OLPC hardware: what if there was an SDR modem / chipset?
dear olpc devel people, i've been doing some research and found a couple of companies with SDR R.F. front-end ICs. one is 40nm and is so tiny that it will only cost about $2, mass-produced. also thanks to being in 40nm, the speed of the (SoC / embedded) ARM9 core is so fast that it's perfectly capable of handling multiple protocols. as you're no doubt aware, Software-Defined Radio has been full of promise for quite some time as The low-cost transceiver option, but it's only recently that the speed of embedded ICs has gone up enough and the geometry small enough to bring the cost down into the affordable range. key to making SDR work is of course having the software :) but, i've found a company who already have GSM through EDGE; there's http://openbts.org and also of course there's the gnu-radio project which has produced part of 802.11, amongst other things. ( but, remember: the nice thing about the 2.4ghz and 5ghz bands is that you don't _actually_ need to do 802.11, you can in fact just use the entire set of bands to do absolutely anything you want. and, with SDR, you _could_ do anything you want). the neat thing about SDR is that the _same_ solution replaces: * a WIFI chipset ($10) * a GSM chipset ($12 lowest i've found in 100k+ volumes) * or a 3G chipset ($30 lowest i've heard about in mass-volume) * a GPS chipset ($6 and that's again an SDR solution, you need a DSP to translate; $12 for dedicated chipset) * a WIMAX chipset (haven't even looked this up, but estimate $20) * a DVB TV chipset (approx $5 and again that's an SDR solution) * an FM Radio chipset (don't know its cost, don't honestly care!) i repeat. all those can be replaced with _one_ i repeat _one_ single solution, costing roughly... $12, if that. issues which need to be resolved: * paying for a minimum of 8 40nm 10in wafers (appx 5000 ICs per wafer) @ $0.50 ea, running the test vectors @ $0.75 ea, packaging @ $0.50 ea it works out roughly at $2.00 times 40,000. * creating the PCB with RF MEMS filters (http://en.wikipedia.org/wiki/RF_MEMS) and other assorted components, coax connectors for antenna, the remaining components are going to be somewhere around $10. * license compliance and Certification in the countries in which the final modem is deployed (remember that if frequencies other than 2.4ghz or 5ghz @ greater than 100mW are used or 400mW in Hong Kong then licenses are NOT required) even with these issues to be costed out and resolved, i wanted to ask: * is the incredible low-cost and flexibility of SDR worth pursuing? * is the current Marvell 88688 proprietary firmware 802.11 blob _that_ acceptable / accepted? * is the possibility of being able to run an XO up a pole (or placed at the top of any tall building) and have it _be_ the GSM or WIMAX base station for an entire town or village and the surrounding countryside for miles around the kind of thing that is attractive to, and useful to the aims of the OLPC project, or not? also - one thing that also would help to have an answer to : if answers above turn out to be resounding yes, what's next? who makes the decision? l. ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: OLPC hardware: what if there was an SDR modem / chipset?
even this could be implemented. http://en.wikipedia.org/wiki/IEEE_802.22 _especially_ 802.22 which is a perfect candidate for SDR because of the need to cooperate, and not interfere with the existing TV transmissions. anything - absolutely, absolutely anything. with SDR, you get _proper_ freedom to develop the communications infrastructure needed for the OLPC laptop users to support themselves and _not_ depend on anyone or anything else. l. ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
offtopic question about high density wifi
this does not directly involve OLPC, but since I know folks here have had to deal with the problem I'm asking for help here. I'm setting up wireless for a confrence in the near future (~1000 people for 3 days in a hotel), I know the RF side of things well and will be doing my best to avoid overlapping channel useage. but my question is if there is a limit (other than the effective limit of the RF channel) on the number of systems that can assocciate with a single access point? if there is a limit on the number of devices that can assocciate with a single AP, then I need to deploy more APs, even though they will interfere with each other on RF. If there isn't such a limit, then I just need to worry about making the best use of the RF spectrum that I can. David Lang ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
quick Forth question
Can anyone help me with a tiny Forth script? Can never quite get my head around the language. I'm trying to set up an if-else based on whether a mfg tag exists (or whether writing a mfg tag succeeded or not) I'm trying: add-tag ak 0 catch if 2drop . Laptop already activated cr then But, if ak already exists, it simply says: Tagname already exists ...rather than executing my conditional code. Also experimented with find-tag but couldn't figure it out. cheers, Daniel ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: OLPC hardware: what if there was an SDR modem / chipset?
Luke, Looks like you have the incorrect link for the Openbts.org. The correct link is now http://openbts.sourceforge.net/ /Robert H. rihowa...@gmail.com linux - the best things in life are free On Jan 25, 2010, at 7:42 AM, Luke Kenneth Casson Leighton wrote: dear olpc devel people, i've been doing some research and found a couple of companies with SDR R.F. front-end ICs. one is 40nm and is so tiny that it will only cost about $2, mass-produced. also thanks to being in 40nm, the speed of the (SoC / embedded) ARM9 core is so fast that it's perfectly capable of handling multiple protocols. as you're no doubt aware, Software-Defined Radio has been full of promise for quite some time as The low-cost transceiver option, but it's only recently that the speed of embedded ICs has gone up enough and the geometry small enough to bring the cost down into the affordable range. key to making SDR work is of course having the software :) but, i've found a company who already have GSM through EDGE; there's http://openbts.org and also of course there's the gnu-radio project which has produced part of 802.11, amongst other things. ( but, remember: the nice thing about the 2.4ghz and 5ghz bands is that you don't _actually_ need to do 802.11, you can in fact just use the entire set of bands to do absolutely anything you want. and, with SDR, you _could_ do anything you want). the neat thing about SDR is that the _same_ solution replaces: * a WIFI chipset ($10) * a GSM chipset ($12 lowest i've found in 100k+ volumes) * or a 3G chipset ($30 lowest i've heard about in mass-volume) * a GPS chipset ($6 and that's again an SDR solution, you need a DSP to translate; $12 for dedicated chipset) * a WIMAX chipset (haven't even looked this up, but estimate $20) * a DVB TV chipset (approx $5 and again that's an SDR solution) * an FM Radio chipset (don't know its cost, don't honestly care!) i repeat. all those can be replaced with _one_ i repeat _one_ single solution, costing roughly... $12, if that. issues which need to be resolved: * paying for a minimum of 8 40nm 10in wafers (appx 5000 ICs per wafer) @ $0.50 ea, running the test vectors @ $0.75 ea, packaging @ $0.50 ea it works out roughly at $2.00 times 40,000. * creating the PCB with RF MEMS filters (http://en.wikipedia.org/wiki/RF_MEMS) and other assorted components, coax connectors for antenna, the remaining components are going to be somewhere around $10. * license compliance and Certification in the countries in which the final modem is deployed (remember that if frequencies other than 2.4ghz or 5ghz @ greater than 100mW are used or 400mW in Hong Kong then licenses are NOT required) even with these issues to be costed out and resolved, i wanted to ask: * is the incredible low-cost and flexibility of SDR worth pursuing? * is the current Marvell 88688 proprietary firmware 802.11 blob _that_ acceptable / accepted? * is the possibility of being able to run an XO up a pole (or placed at the top of any tall building) and have it _be_ the GSM or WIMAX base station for an entire town or village and the surrounding countryside for miles around the kind of thing that is attractive to, and useful to the aims of the OLPC project, or not? also - one thing that also would help to have an answer to : if answers above turn out to be resounding yes, what's next? who makes the decision? l. ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: OLPC hardware: what if there was an SDR modem / chipset?
i've been doing some research and found a couple of companies with SDR R.F. front-end ICs. one is 40nm and is so tiny that it will only cost about $2, mass-produced. also thanks to being in 40nm, the speed of vs i repeat. all those can be replaced with _one_ i repeat _one_ single solution, costing roughly... $12, if that. Was the first $2 a typo or maybe I do not get something? ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: OLPC hardware: what if there was an SDR modem / chipset?
On Mon, 25 Jan 2010, Luke Kenneth Casson Leighton wrote: i've been doing some research and found a couple of companies with SDR R.F. front-end ICs. one is 40nm and is so tiny that it will only cost about $2, mass-produced. also thanks to being in 40nm, the speed of the (SoC / embedded) ARM9 core is so fast that it's perfectly capable of handling multiple protocols. as you're no doubt aware, are you sure that your $2 SDR chip is going to be able to do a protocol as complex as wifi? that will take quite a bit of computing power (digital signal processing isn't something you do efficiantly on the ARM9 core), so it may push you from the $2 chip to a $10 chip (what do you think the existing wifi chipsets are?) Software-Defined Radio has been full of promise for quite some time as The low-cost transceiver option, but it's only recently that the speed of embedded ICs has gone up enough and the geometry small enough to bring the cost down into the affordable range. key to making SDR work is of course having the software :) but, i've found a company who already have GSM through EDGE; there's http://openbts.org and also of course there's the gnu-radio project which has produced part of 802.11, amongst other things. ( but, remember: the nice thing about the 2.4ghz and 5ghz bands is that you don't _actually_ need to do 802.11, you can in fact just use the entire set of bands to do absolutely anything you want. and, with SDR, you _could_ do anything you want). but if you don't do 802.11a/b/g/n you won't be able to talk to other devices. the neat thing about SDR is that the _same_ solution replaces: * a WIFI chipset ($10) * a GSM chipset ($12 lowest i've found in 100k+ volumes) * or a 3G chipset ($30 lowest i've heard about in mass-volume) * a GPS chipset ($6 and that's again an SDR solution, you need a DSP to translate; $12 for dedicated chipset) * a WIMAX chipset (haven't even looked this up, but estimate $20) * a DVB TV chipset (approx $5 and again that's an SDR solution) * an FM Radio chipset (don't know its cost, don't honestly care!) i repeat. all those can be replaced with _one_ i repeat _one_ single solution, costing roughly... $12, if that. while the chip can decode all the different protocols you mention below, the problem is that these cover many different frequency ranges, and getting the RF portion of the device (including antennas) to handle all those different bands on one device, let alone at one time, is far more complex than you imagine (and would you really want a device that could be wifi, OR GPS OR but not more than one at a time?) it's bad enough if you are just needing to receive all these different frequencies, but if you have to transmit on them it takes even more work (several of your items are receive only, but the critical ones require transmit capability) you also ignore licensing and regulatory approval. That actually amounts to a significant portion of some of the chipsets. you can avoid that by eliminating those items from your list, but that also reduces the attractivness of the solution. David Lang issues which need to be resolved: * paying for a minimum of 8 40nm 10in wafers (appx 5000 ICs per wafer) @ $0.50 ea, running the test vectors @ $0.75 ea, packaging @ $0.50 ea it works out roughly at $2.00 times 40,000. * creating the PCB with RF MEMS filters (http://en.wikipedia.org/wiki/RF_MEMS) and other assorted components, coax connectors for antenna, the remaining components are going to be somewhere around $10. * license compliance and Certification in the countries in which the final modem is deployed (remember that if frequencies other than 2.4ghz or 5ghz @ greater than 100mW are used or 400mW in Hong Kong then licenses are NOT required) even with these issues to be costed out and resolved, i wanted to ask: * is the incredible low-cost and flexibility of SDR worth pursuing? * is the current Marvell 88688 proprietary firmware 802.11 blob _that_ acceptable / accepted? * is the possibility of being able to run an XO up a pole (or placed at the top of any tall building) and have it _be_ the GSM or WIMAX base station for an entire town or village and the surrounding countryside for miles around the kind of thing that is attractive to, and useful to the aims of the OLPC project, or not? also - one thing that also would help to have an answer to : if answers above turn out to be resounding yes, what's next? who makes the decision? l. ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: OLPC hardware: what if there was an SDR modem / chipset?
On Mon, 25 Jan 2010, NoiseEHC wrote: i've been doing some research and found a couple of companies with SDR R.F. front-end ICs. one is 40nm and is so tiny that it will only cost about $2, mass-produced. also thanks to being in 40nm, the speed of vs i repeat. all those can be replaced with _one_ i repeat _one_ single solution, costing roughly... $12, if that. Was the first $2 a typo or maybe I do not get something? he claims $10 for the board and other components to drive the $2 chip. David Lang ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: quick Forth question
On Mon, Jan 25, 2010 at 10:59, Daniel Drake d...@laptop.org wrote: Can anyone help me with a tiny Forth script? Can never quite get my head around the language. I once wrote pen plotter programs in FORTH for fractals, to test the plotter mechanism. Hypnotic. I'm trying to set up an if-else based on whether a mfg tag exists (or whether writing a mfg tag succeeded or not) I'm trying: add-tag ak 0 catch if 2drop . Laptop already activated cr then But, if ak already exists, it simply says: Tagname already exists ...rather than executing my conditional code. That isn't very FORTHish, to have the argument to add-tag come after. Is that right? Your description is incomplete, and looks incorrect. My guess is that add-tag gives you the Tagname already exists message, and then FORTH continues, executing your conditional when it gets to it, and dropping two items from the stack. Please check. Here is what we need in order to comment usefully: Stack picture before starting. Expected result of add-tag, with stack picture. Expected result of ak, with stack picture. Is ak the address of a string? We're OK about putting 0 on the stack. Expected result of catch, with stack picture. Once you have all of that, you may not need our help. You can compare it with what actually happens by inserting stack display words. Also experimented with find-tag but couldn't figure it out. cheers, Daniel ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel -- Edward Mokurai (默雷/धर्ममेघशब्दगर्ज/دھرممیگھشبدگر ج) Cherlin Silent Thunder is my name, and Children are my nation. The Cosmos is my dwelling place, the Truth my destination. http://www.earthtreasury.org/ ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: quick Forth question
daniel wrote: Can anyone help me with a tiny Forth script? Can never quite get my head around the language. I'm trying to set up an if-else based on whether a mfg tag exists (or whether writing a mfg tag succeeded or not) I'm trying: add-tag ak 0 catch if 2drop . Laptop already activated cr then maybe something like: ak find-tag if 2drop . Laptop already activated cr then i'm pretty much a neophyte too, but i believe the commands that one types at the ok prompt that feel like command, with trailing args, should be avoided when scripting. i'm sure they can be used, but no doubt some special sauce is needed. paul But, if ak already exists, it simply says: Tagname already exists ...rather than executing my conditional code. Also experimented with find-tag but couldn't figure it out. cheers, Daniel ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel =- paul fox, p...@laptop.org ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: quick Forth question
On 01/25/2010 12:05 PM, Paul Fox wrote: maybe something like: ak find-tag if 2drop . Laptop already activated cr then i'm pretty much a neophyte too, but i believe the commands that one types at the ok prompt that feel like command, with trailing args, should be avoided when scripting. i'm sure they can be used, but no doubt some special sauce is needed. I worked it out. : check-ak add-tag ak 0 eval ; ok ' check-ak catch if . Laptop already activated cr then If you want to use it in a word then you need ['] rather than ' : do-me ['] check-ak catch if . Laptop already activated cr then ok do-me You can think of ' as the C operator. ' gets the reference to the word and that's what you have to give to catch so it can grab the exception. -- Richard A. Smith rich...@laptop.org One Laptop per Child ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: OLPC hardware: what if there was an SDR modem / chipset?
On Mon, Jan 25, 2010 at 4:24 PM, da...@lang.hm wrote: On Mon, 25 Jan 2010, Luke Kenneth Casson Leighton wrote: i've been doing some research and found a couple of companies with SDR R.F. front-end ICs. one is 40nm and is so tiny that it will only cost about $2, mass-produced. also thanks to being in 40nm, the speed of the (SoC / embedded) ARM9 core is so fast that it's perfectly capable of handling multiple protocols. as you're no doubt aware, are you sure that your $2 SDR chip is going to be able to do a protocol as complex as wifi? the $ RF front-end chip ends at an A-D / D-A converter. after that, it's well known that DSPs can handle the rest of the work. that will take quite a bit of computing power (digital signal processing isn't something you do efficiantly on the ARM9 core), so it may push you from the $2 chip to a $10 chip (what do you think the existing wifi chipsets are?) ARM9 or ARM7 cores plus a DSP. while the chip can decode all the different protocols you mention below, the problem is that these cover many different frequency ranges, and getting the RF portion of the device (including antennas) to handle all those different bands on one device, let alone at one time, is far more complex than you imagine and there is expertise in the world to take care of it. admittedly it's an area where the expertise is becoming increasingly rare, but the expertise exists. (and would you really want a device that could be wifi, OR GPS OR but not more than one at a time?) a) two $2 transceiver chips - knock yourself out! :) b) i believe that the RF transceiver chip is multi-channel (simultaneous) so can actually handle two separate protocols at once. either way, it's just extra load on the DSP. you also ignore licensing and regulatory approval. no, i didn't, but it's worth mentioning again so that it's not forgotten as part of the cost. the key questions to be asking are: in light of the massive volumes involved with OLPC XOs, is SDR worth pursuing, given all the development costs, but given all the benefits especially where SDR can be re-programmed to do whatever in bands where licensing and regulatory approval is _not_ required, on a per-country basis? l. ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: OLPC hardware: what if there was an SDR modem / chipset?
On Mon, Jan 25, 2010 at 6:05 PM, Luke Kenneth Casson Leighton l...@lkcl.net wrote: the key questions to be asking are: in light of the massive volumes involved with OLPC XOs, is SDR worth pursuing, given all the development costs, but given all the benefits especially where SDR can be re-programmed to do whatever in bands where licensing and regulatory approval is _not_ required, on a per-country basis? bearing in mind that the particular R.F. front-end transceiver chips i'm looking at, one can do 600mhz to 6ghz and the other can do 100mhz to 6ghz. there's another one which can do 80mhz to around 5ghz or so i believe, but it's receive only but has far superior signal-to-noise ratio and is accompanied by a far superior A2D-USB2 converter. l. ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: OLPC hardware: what if there was an SDR modem / chipset?
On Mon, Jan 25, 2010 at 4:25 PM, da...@lang.hm wrote: On Mon, 25 Jan 2010, NoiseEHC wrote: i've been doing some research and found a couple of companies with SDR R.F. front-end ICs. one is 40nm and is so tiny that it will only cost about $2, mass-produced. also thanks to being in 40nm, the speed of vs i repeat. all those can be replaced with _one_ i repeat _one_ single solution, costing roughly... $12, if that. Was the first $2 a typo or maybe I do not get something? he claims $10 for the board and other components to drive the $2 chip. yeah, roughly. RF MEMS are the cheapest filters needed. the $2 chip basically has an A2D and a D2A so the Intermediate Frequencies come out as Digital. check the design of the USRP for example to see how it all fits together. i'm still finding out about this stuff and tracking it down but i had enough to say this is what's known right now: is it worth it? even at this early stage. l. ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: OLPC hardware: what if there was an SDR modem / chipset?
On Mon, 25 Jan 2010, Luke Kenneth Casson Leighton wrote: On Mon, Jan 25, 2010 at 4:24 PM, da...@lang.hm wrote: On Mon, 25 Jan 2010, Luke Kenneth Casson Leighton wrote: i've been doing some research and found a couple of companies with SDR R.F. front-end ICs. one is 40nm and is so tiny that it will only cost about $2, mass-produced. also thanks to being in 40nm, the speed of the (SoC / embedded) ARM9 core is so fast that it's perfectly capable of handling multiple protocols. as you're no doubt aware, are you sure that your $2 SDR chip is going to be able to do a protocol as complex as wifi? the $ RF front-end chip ends at an A-D / D-A converter. after that, it's well known that DSPs can handle the rest of the work. it's not just 'a RF front-end chip', it can get as bad as a RF receiver chip for each band, plus a RF transmitter chip for each band, plus switching logic to switch between them, that will take quite a bit of computing power (digital signal processing isn't something you do efficiantly on the ARM9 core), so it may push you from the $2 chip to a $10 chip (what do you think the existing wifi chipsets are?) ARM9 or ARM7 cores plus a DSP. which drives up the cost while the chip can decode all the different protocols you mention below, the problem is that these cover many different frequency ranges, and getting the RF portion of the device (including antennas) to handle all those different bands on one device, let alone at one time, is far more complex than you imagine and there is expertise in the world to take care of it. admittedly it's an area where the expertise is becoming increasingly rare, but the expertise exists. this is expensive expertise to hire. (and would you really want a device that could be wifi, OR GPS OR but not more than one at a time?) a) two $2 transceiver chips - knock yourself out! :) b) i believe that the RF transceiver chip is multi-channel (simultaneous) so can actually handle two separate protocols at once. either way, it's just extra load on the DSP. no, it's seperate portions of the RF spectrum that need to be tuned and downconverted to a frequency range the DSP can deal with. those are the more difficult parts of the device to get right. you also ignore licensing and regulatory approval. no, i didn't, but it's worth mentioning again so that it's not forgotten as part of the cost. the key questions to be asking are: in light of the massive volumes involved with OLPC XOs, is SDR worth pursuing, given all the development costs, but given all the benefits especially where SDR can be re-programmed to do whatever in bands where licensing and regulatory approval is _not_ required, on a per-country basis? probably not, for the same reason that OLPC isn't writing it's own OS anymore. it requires extensive expertise and tools that they don't have. they funded the developement and deployment of the screen technology, but everything else has been assembling off-the-shelf chips and subsystems, and with the changeing times, they have less engineering expertise than they used to. David Lang ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: OLPC hardware: what if there was an SDR modem / chipset?
On Mon, 25 Jan 2010, Luke Kenneth Casson Leighton wrote: On Mon, Jan 25, 2010 at 6:05 PM, Luke Kenneth Casson Leighton l...@lkcl.net wrote: the key questions to be asking are: in light of the massive volumes involved with OLPC XOs, is SDR worth pursuing, given all the development costs, but given all the benefits especially where SDR can be re-programmed to do whatever in bands where licensing and regulatory approval is _not_ required, on a per-country basis? bearing in mind that the particular R.F. front-end transceiver chips i'm looking at, one can do 600mhz to 6ghz and the other can do 100mhz to 6ghz. there's another one which can do 80mhz to around 5ghz or so i believe, but it's receive only but has far superior signal-to-noise ratio and is accompanied by a far superior A2D-USB2 converter. please point me at these magic chips, I would like to use them in my own projects. I'll bet that these chips can operate in that band, but not throughout the band without changing external components. David Lang ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: OLPC hardware: what if there was an SDR modem / chipset?
On Mon, Jan 25, 2010 at 4:24 PM, da...@lang.hm wrote: imagine (and would you really want a device that could be wifi, OR GPS OR but not more than one at a time?) http://www.limemicro.com/products.php you can see, from the evaluation board, that there are _fourteen_ separate R.F. coax connectors, and that the product description says listen for GSM stuff as well as transmit. also it's 375mhz to 4ghz not 600mhz to 6ghz as i vaguely remember saying earlier. the other one is definitely 100mhz to 6ghz though. l. ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: OLPC hardware: what if there was an SDR modem / chipset?
On Mon, 25 Jan 2010, Luke Kenneth Casson Leighton wrote: On Mon, Jan 25, 2010 at 4:24 PM, da...@lang.hm wrote: imagine (and would you really want a device that could be wifi, OR GPS OR but not more than one at a time?) http://www.limemicro.com/products.php you can see, from the evaluation board, that there are _fourteen_ separate R.F. coax connectors, and that the product description says listen for GSM stuff as well as transmit. also it's 375mhz to 4ghz not 600mhz to 6ghz as i vaguely remember saying earlier. the other one is definitely 100mhz to 6ghz though. interesting specs, I wish there was a datasheet and pricing available for download. I've registered with them so we'll see when they get back to me. David Lang ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: offtopic question about high density wifi
2010/1/25 da...@lang.hm: but my question is if there is a limit (other than the effective limit of the RF channel) on the number of systems that can assocciate with a single access point? Yes - APs often have a limit. The limit is not defined by any kind of specification. It depends on the AP. Daniel ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: OLPC hardware: what if there was an SDR modem / chipset?
On Mon, Jan 25, 2010 at 6:52 PM, da...@lang.hm wrote: http://www.limemicro.com/products.php you can see, from the evaluation board, that there are _fourteen_ separate R.F. coax connectors, and that the product description says listen for GSM stuff as well as transmit. also it's 375mhz to 4ghz not 600mhz to 6ghz as i vaguely remember saying earlier. the other one is definitely 100mhz to 6ghz though. interesting specs, I wish there was a datasheet and pricing available for download. I've registered with them so we'll see when they get back to me. this stuff is juuust at the point where it's ready for mass-production. ordinarily this stuff would be snapped up by e.g. qualcomm etc. but i believe this is going to be different: the companies involved are ... well, they're fully aware that it's disruptive technology. the important thing is therefore to make an introduction into markets which DO NOT conflict with The Big Boys i.e. introduce finished useable modems into third world countries, emerging markets etc. which The Big Boys have completely written off due to lack of profitable opportunities. in other words, because the base stations are so expensive and will either get eaten by cows or be stripped down for spare parts and the copper wire (let's be honest _and_ cynical at the same time, why not...) third world and emerging markets won't _get_ any WIMAX, 3G or LTE base stations. so, there's therefore a wide-open opportunity to deploy SDR modems which can be reprogrammed as a poor-man's Base Station in a pinch, mayybe have a better external antenna attached to it. if the on-board DSP and ARM CPU can't cope with more than 4 simultaneous users _wow_ so what, big damn deal, that's 4 more users than they've ever had in the area before _and_ there's no data charges. overall it's a completely unattractive financial opportunity _except_ for the manufacturers of the SDR modems and even then the cost will be so low, the profit margins so slim, the upgrade incentives you see in the 1st world are so just... not even there... basically what i'm saying is that it's a completely completely different game (from the 1st world handset/smartphone/basestation market), and it's one that has OLPC and OLPP (one laptop per person) written all over it. it just so happens that the same SDR chipsets could also be used to increase profit margins in the 1st world but that's another story: the markets i'm interested in seeing SDR modems / handsets deployed are clearly separate and distinct, which the 1st world corporations with vested and legacy interests to protect _just_ won't be interested in, thank god. l. ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: offtopic question about high density wifi
Hi, Yes - APs often have a limit. The limit is not defined by any kind of specification. It depends on the AP. I think I recall that brief testing with a bunch of consumer access points at OLPC showed that this number was usually above 15 clients and below 30 clients, per AP, at 54Mbps. For hosting hundreds of devices, you should look into getting many access points that each have three omni-directional antennas working on non-overlapping channels. The PyCon wifi team does a write-up about their setup each year, which seems to contain more information than anyone could need: http://www.tummy.com/Community/Articles/pycon2007-network/ http://www.tummy.com/Community/Articles/pycon2008-network/ http://www.tummy.com/Community/Articles/pycon2009-network/ - Chris. -- Chris Ball c...@laptop.org One Laptop Per Child ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: OLPC hardware: what if there was an SDR modem / chipset?
On Mon, Jan 25, 2010 at 6:35 PM, da...@lang.hm wrote: [...] projects. I'll bet that these chips can operate in that band, but not throughout the band without changing external components. certainly mirics 80mhz-5ghz receiver chip has multiple RF inputs and has i think it looks like it has 3 separate RF down-converters all capable of running simultaneously, so it could do e.g. FM Radio and DVB-T at the same time. whilst i don't have enough info at this stage to confirm whether that's the case in the two transceiver chips i _do_ expect it to be so, simply because... well... the designers would have to be daft not to have done it! :) so, i expect that the chips will be able to operate in several wildly different frequencies simultaneously, _if_ set up with several sets of appropriate external components (with matching antenna) but again: too early to tell, yet; i'll have more info later as my research progresses. the point is, however, to establish the actual cost of a multi-frequency SDR modem in OLPC-level mass volume, and see if it's viable. _orrr_ establish whether the next gen OLPC hardware could put in a standard interface such as PCI-e (USB2 not SATA/PATA) which could easily be used to slot in an Intel 5350 WIMAX (or even pffh one of the PCI-e 3G modems from Huawei such as the EM775 or EM770); that would then be future-proof upgradeable, so that if a multi-frequency SDR modem ever came out in 50x30mm or 24x30mm mini PCI-e form-factor, it could just be slotted in without a PCB redesign. worth thinking about? l. ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: OLPC hardware: what if there was an SDR modem / chipset?
On Mon, Jan 25, 2010 at 6:33 PM, da...@lang.hm wrote: the key questions to be asking are: in light of the massive volumes involved with OLPC XOs, is SDR worth pursuing, given all the development costs, but given all the benefits especially where SDR can be re-programmed to do whatever in bands where licensing and regulatory approval is _not_ required, on a per-country basis? probably not, for the same reason that OLPC isn't writing it's own OS anymore. it requires extensive expertise and tools that they don't have. they funded the developement and deployment of the screen technology, but everything else has been assembling off-the-shelf chips and subsystems, and with the changeing times, they have less engineering expertise than they used to. ok - i'm asking the wrong question :) let's assume that somewhere in 2010 an SDR modem exists (from someone, doesn't matter who made it). let's assume that software is available (COTS) and is (perhaps temporarily, perhaps permanently) proprietary and turns on the SDR for specific functions. let's assume also that the specs on the SDR RF side are completely documented, publicly available and, importantly, useable by free software (for the future, for replacing the COTS firmware). let's assume that the SDR modem and the COTS firmware which actually turns it into WIMAX, 3G, GSM, 802.11 etc. is available; let's assume that the SDR modem comes with instructions just plug in this 802.11 antenna here; just plug in this Quad-band Penta-band GSM/3G antenna here; just plug in the GPS antenna here. _if_ all these things were true, _would_ the OLPC hardware design team select such a COTS modem and its associated firmware (over-and-above the rather dull Marvell 88688 option being deployed right now in XO-1)? and if so, who do i need to talk to, to get a yes from? (and if not, what _would_ it take for an SDR modem to be selected?) this last is perhaps the key question. what's it going to take to get an SDR modem into a future XO? l. ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: quick Forth question
2010/1/25 Richard A. Smith rich...@laptop.org: I worked it out. : check-ak add-tag ak 0 eval ; ok ' check-ak catch if . Laptop already activated cr then Thanks muchly! It works well. Daniel ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Lots of broken chargers in Nicaragua
Hi, What seems to be a lesser-common problem in the other deployments I have seen seems to be quite common here: chargers are breaking due to damage to the cable and the point where the cable enters the big green plug that goes into the power socket. Although these problems seem to be due to carelessness with the chargers, it would certainly help this deployment if the units were stronger. This is a significant problem here. A project partner here has been able to repair almost all of the broken units by reinforcing the cables and sometimes swapping out the components inside the charger unit itself. I'll send in more details once they arrive. Daniel ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: offtopic question about high density wifi
Chris and Daniel are right. Doing this with SOHO APs is going to be difficult - it would require over 25 APs. You have moved into a area where you are probably better off using high-priced (i.e. multiple antenna) APs, and a centralized controller. wad On Jan 25, 2010, at 11:57 PM, da...@lang.hm wrote: this does not directly involve OLPC, but since I know folks here have had to deal with the problem I'm asking for help here. I'm setting up wireless for a confrence in the near future (~1000 people for 3 days in a hotel), I know the RF side of things well and will be doing my best to avoid overlapping channel useage. but my question is if there is a limit (other than the effective limit of the RF channel) on the number of systems that can assocciate with a single access point? if there is a limit on the number of devices that can assocciate with a single AP, then I need to deploy more APs, even though they will interfere with each other on RF. If there isn't such a limit, then I just need to worry about making the best use of the RF spectrum that I can. David Lang ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: Touchpad accel, spirals and xset
Sorry for the delayed response, I think I need to play around and compile a kernel module and then use it on the xo-1. But to answer a few of the questions... The init of the psmouse module triggers a calibration. that's certainly true, but i think it happens pretty early -- the kernel is initialized by the time the dots start circling the XO guy. and we don't really have any control over it. In the GS spec, 7.3.1 it mentions sensor correction being done automatically at startup, and the sending of AA and 00 once complete. Then in 7.5 Section 6) Sensor calibration execution command it says to When Power-up is done, do the self adjustment... Once I'm able I will test a module without the INIT_DELAYED_WORK(priv-recalib_wq, hgpk_recalib_work); on driver init, and rely on the spew recalibration to be its first calibration. A bit of an experiment... why do you think that the when the pad emits streams of packets on its own, which don't represent any real motion, that it's not a bug? I believe it is noise, which is easily filtered out either at the driver level, or with xset m threshold. At a guess I'd say it is auto-tuning of the cells to get rid of low frequency noise, like a blob of dirt/water that maybe sitting in a corner of the pad uninterrupted. A little bit of testing (with recalibrations turned off) I find it compensates well against the presence of a tiny key on the pad (big interference, and fixed), ie can still correctly and accurately move around. But the pad does not immediately compensate back once the interference (key) is removed, instead it just wabbles around by 1 or 2 pixels (sound familiar ;) Perhaps this is a cause of spew? In this state I found that tracking could work ok, but tapping the pad produced a fixed jump in the curser depending on where I tapped. Sometimes it stopped sooner, other times not after a while. Note, this is still with spew recalibration turned off. I suspect if I turned it on, a moment away from the pad and I'd be back to accurate tracking and no deltas if I tapped the pad. Just tested now, and yes, with spew recalib on (a spew_delay of 1), and interference removed, I quickly gain accurate and correct control. i think you may not be aware of the long history of issues with this touchpad. fixing the pad's errant behavior in the lab, or in a climate controlled home, is easy. the touchpads don't misbehave in those conditions, much. but in the uncontrolled environment of a classroom in the developing world, all bets are off. kids have dirty hands, or lick their fingers, or work in a dusty (chalk dust?) environment, or often tend to have two hands close to the touchpad at once, or, or, or... the list goes on. Looking at the spec sheet again, I noticed its operating conditions go to 95% non-condensing humidity, and operating temperatures upto 50degreesC. But in essence the problems in the field, are just some form of interference or another, and its what we decide the driver should do or what we should we let the pad firmware do that is the question. i'm all for having a deployment that's having touchpad troubles try simply turning off jumpyness recalibration -- i'd love to be proven wrong -- but i don't think it will work well. I refer to my earlier testing with the key. Note, at this point in time my housemate has offered me some yoghurt... Interference as yoghurt (blob in the corner) seems to be harder for the pad to compensate against than the key. Perhaps because it does not max out the sensors as much not being metal. This is with spew_delay off again. Turning the spew_delay back to 1 rapidly gives me correct control, and fixed tapping with no delta. Even when removing the blob (smearing it across the pad in the process) I think this is enough experimenting for now, and a field test would be great... :) jumpy_delay of 0, spew_delay of 1. it's certainly nice having someone else looking at the problem(s) with a fresh perspective. thank you. (and don't let my negative response deter you -- you might well be on to something -- who knows?) Yes its important to critique in the hope of getting to the bottom of this and deciding what is the best solution. James. ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: Touchpad accel, spirals and xset
james wrote: Sorry for the delayed response, I think I need to play around and compile a kernel module and then use it on the xo-1. But to answer a few of the questions... The init of the psmouse module triggers a calibration. that's certainly true, but i think it happens pretty early -- the kernel is initialized by the time the dots start circling the XO guy. and we don't really have any control over it. In the GS spec, 7.3.1 it mentions sensor correction being done automatically at startup, and the sending of AA and 00 once complete. Then in 7.5 Section 6) Sensor calibration execution command it says to When Power-up is done, do the self adjustment... Once I'm able I will test a module without the INIT_DELAYED_WORK(priv-recalib_wq, hgpk_recalib_work); on driver init, and rely on the spew recalibration to be its first calibration. A bit of an experiment... that call doesn't cause a recalibration. it only sets up the work queue infrastructure so that later calls to: psmouse_queue_work(psmouse, priv-recalib_wq, ... ) can work. you can see from dmesg that we already don't force a recalibration at init time. paul =- paul fox, p...@laptop.org ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: Lots of broken chargers in Nicaragua
On 01/25/2010 04:31 PM, Daniel Drake wrote: Hi, What seems to be a lesser-common problem in the other deployments I have seen seems to be quite common here: chargers are breaking due to damage to the cable and the point where the cable enters the big green plug that goes into the power socket. Although these problems seem to be due to carelessness with the chargers, it would certainly help this deployment if the units were stronger. This is a significant problem here. A project partner here has been able to repair almost all of the broken units by reinforcing the cables and sometimes swapping out the components inside the charger unit itself. I'll send in more details once they arrive. The abuse case is a trade off. Without adding a lot of expense beefing up all the parts in the chain something has to fail its just a question of what. In the XO we decided that we wanted the cable to fail rather than the laptop. The mechanical coupling of the DC jack at the XO is stronger than the cable. The plug is straight rather than right angle in hopes that it would separate from the jack in high stress events but if the force is perpendicular to the jack then its still going to bind. Reinforcing the cable without careful analysis may cause failure at the XO rather than in the cable. As new power adapters are much cheaper than new laptop motherboards they should probably take a closer look at how the cable is getting yanked and attack that problem rather than beefing up the cable. -- Richard A. Smith rich...@laptop.org One Laptop per Child ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: Lots of broken chargers in Nicaragua
On Mon, Jan 25, 2010 at 03:31:24PM -0600, Daniel Drake wrote: chargers are breaking due to damage to the cable and (sic) the point where the cable enters the big green plug that goes into the power socket. I agree with Richard, something has to fail, and the cable should be the thing to fail rather than the laptop ... and the point where the cable exits the strain relief of either end is what should fail. But my original reading of what you said suggests the failures are at the AC end of the cable ... the power supply housing is a big green plug and it goes into the wall power socket. Which is it? -- James Cameron http://quozl.linux.org.au/ ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: Lots of broken chargers in Nicaragua
On 01/25/2010 09:27 PM, James Cameron wrote: But my original reading of what you said suggests the failures are at the AC end of the cable ... the power supply housing is a big green plug and it goes into the wall power socket. Which is it? I'll add that we have one other report from Nepal of the cable failing. There we believe its the kids pulling the laptop out of the charging rack and forgetting to unplug it first. For Nepal it fails at both the connection to the power brick and at the connection to the barrel connector with the largest number of failures occurring at the barrel. -- Richard A. Smith rich...@laptop.org One Laptop per Child ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: OLPC hardware: what if there was an SDR modem / chipset?
On Mon, 25 Jan 2010, Luke Kenneth Casson Leighton wrote: ok - i'm asking the wrong question :) let's assume that somewhere in 2010 an SDR modem exists (from someone, doesn't matter who made it). let's assume that software is available (COTS) and is (perhaps temporarily, perhaps permanently) proprietary and turns on the SDR for specific functions. let's assume also that the specs on the SDR RF side are completely documented, publicly available and, importantly, useable by free software (for the future, for replacing the COTS firmware). let's assume that the SDR modem and the COTS firmware which actually turns it into WIMAX, 3G, GSM, 802.11 etc. is available; let's assume that the SDR modem comes with instructions just plug in this 802.11 antenna here; just plug in this Quad-band Penta-band GSM/3G antenna here; just plug in the GPS antenna here. _if_ all these things were true, _would_ the OLPC hardware design team select such a COTS modem and its associated firmware (over-and-above the rather dull Marvell 88688 option being deployed right now in XO-1)? and if so, who do i need to talk to, to get a yes from? (and if not, what _would_ it take for an SDR modem to be selected?) they already ditched the Marvell option that was in the XO-1 for the XO-1.5 that's nearing production. this last is perhaps the key question. what's it going to take to get an SDR modem into a future XO? I'm pretty sure that if there is a SDR that's comparibly priced and has good linux (and unfortunantly, windows) drivers it would be a strong candidate for a future XO. they have always been interested in using open hardware (with the Marvell, they were promised open firmware, but it was never delivered). David Lang ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: OLPC hardware: what if there was an SDR modem / chipset?
On Jan 26, 2010, at 2:07 AM, Luke Kenneth Casson Leighton wrote: On Mon, Jan 25, 2010 at 6:05 PM, Luke Kenneth Casson Leighton l...@lkcl.net wrote: the key questions to be asking are: in light of the massive volumes involved with OLPC XOs, is SDR worth pursuing, given all the development costs, but given all the benefits especially where SDR can be re-programmed to do whatever in bands where licensing and regulatory approval is _not_ required, on a per-country basis? bearing in mind that the particular R.F. front-end transceiver chips i'm looking at, one can do 600mhz to 6ghz and the other can do 100mhz to 6ghz. there's another one which can do 80mhz to around 5ghz or so i believe, but it's receive only but has far superior signal-to-noise ratio and is accompanied by a far superior A2D-USB2 converter. A USB2 interface is used to talk to the A/D ? I just eliminated all the internal USB buses in the XO... I'm not against SDR, but this chip doesn't sound compatible with our power/cost budget. More importantly, this sounds like it is years of software development and testing from being a real product. OLPC doesn't have the resources to fund this development. Re certifications, on both XO-1 and XO-1.5 we use slightly non-standard modules (on XO-1 to support 802.11s, on XO-1.5 to reduce power consumption by 50%) and have payed the full certification costs. They run about 100K$ for starters, with each additional country adding around 5K$. Cheers, wad ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: offtopic question about high density wifi
On Mon, 25 Jan 2010, Chris Ball wrote: Hi, Yes - APs often have a limit. The limit is not defined by any kind of specification. It depends on the AP. I think I recall that brief testing with a bunch of consumer access points at OLPC showed that this number was usually above 15 clients and below 30 clients, per AP, at 54Mbps. For hosting hundreds of devices, you should look into getting many access points that each have three omni-directional antennas working on non-overlapping channels. The PyCon wifi team does a write-up about their setup each year, which seems to contain more information than anyone could need: http://www.tummy.com/Community/Articles/pycon2007-network/ http://www.tummy.com/Community/Articles/pycon2008-network/ http://www.tummy.com/Community/Articles/pycon2009-network/ I've read through these, and they have a lot of useful info. I do have good RF experiance (and even some halfway decent tools for looking at things), but I didn't know what, if any limits there were on the number of clients other than what can be supported by the available airtime. David Lang ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: OLPC hardware: what if there was an SDR modem / chipset?
On Jan 26, 2010, at 4:58 AM, Luke Kenneth Casson Leighton wrote: On Mon, Jan 25, 2010 at 6:33 PM, da...@lang.hm wrote: the key questions to be asking are: in light of the massive volumes involved with OLPC XOs, is SDR worth pursuing, given all the development costs, but given all the benefits especially where SDR can be re-programmed to do whatever in bands where licensing and regulatory approval is _not_ required, on a per-country basis? probably not, for the same reason that OLPC isn't writing it's own OS anymore. it requires extensive expertise and tools that they don't have. they funded the developement and deployment of the screen technology, but everything else has been assembling off-the-shelf chips and subsystems, and with the changeing times, they have less engineering expertise than they used to. ok - i'm asking the wrong question :) let's assume that somewhere in 2010 an SDR modem exists (from someone, doesn't matter who made it). let's assume that software is available (COTS) and is (perhaps temporarily, perhaps permanently) proprietary and turns on the SDR for specific functions. let's assume also that the specs on the SDR RF side are completely documented, publicly available and, importantly, useable by free software (for the future, for replacing the COTS firmware). let's assume that the SDR modem and the COTS firmware which actually turns it into WIMAX, 3G, GSM, 802.11 etc. is available; let's assume that the SDR modem comes with instructions just plug in this 802.11 antenna here; just plug in this Quad-band Penta-band GSM/3G antenna here; just plug in the GPS antenna here. _if_ all these things were true, _would_ the OLPC hardware design team select such a COTS modem and its associated firmware (over-and-above the rather dull Marvell 88688 option being deployed right now in XO-1)? The XO-1 uses the 88W8388, which I've never heard anyone describe as dull before... The XO-1.5 uses the 88W8686, which I hope is nice and dull from an engineering point of view (it has been so far.) and if so, who do i need to talk to, to get a yes from? speaking (and if not, what _would_ it take for an SDR modem to be selected?) this last is perhaps the key question. what's it going to take to get an SDR modem into a future XO? Equivalent performance, for an equivalent cost and power budget. Whether to use fixed hardware or software is a frequent engineering decision. At the prices you quoted, I can currently get multiple dedicated hardware interfaces for the same price, and almost certainly for lower power. The certification issues for SDR haven't been settled, either. I don't know of any products w. SDR shipping with user modifiable software at this time. Can you point me to some ? Cheers, wad ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: offtopic question about high density wifi
On Mon, Jan 25, 2010 at 10:31 PM, da...@lang.hm wrote: I've read through these, and they have a lot of useful info. I do have good RF experiance (and even some halfway decent tools for looking at things), but I didn't know what, if any limits there were on the number of clients other than what can be supported by the available airtime. Lots of very subtle protocol limits, having to do with all sorts of random mostly-timing related parameters where the 802.11 spec gives implementers a lot of freedom to choose arbitrary values. *Plus* the details of all your clients. There are all sorts of fancy algorithms you can use to tune your AP, but all it takes is one bad client and everything goes to hell. And that's completely apart from the arbitrary software limits that some access point manufacturers include, in order to differentiate their consumer and professional product lines. *And* not accounting for stupid software which decides to use the broadcast features of 802.11, which chew up bandwidth 50x faster than normal data does. So, basically: theory is no substitute for experience. It's not really the protocol that's the limit, it's the particular choices that particular access point makes and the choices that common clients and common software make. So your best bet is really to (a) find someone who's done it before, and slavishly copy their setup (variations that you think are trivial, like between firmware revisions, may in fact be critical), or (b) find a company who's invested the time and money to figure out all the variables and do the real world testing, and fork over the $$$ for the commercial quality or pro grade or whatever-they-call-it access point with a guarantee about the number of clients it can support. And a couple of accessible wired switches and wired internet kiosks will go a long way toward mitigating your downside if it turns out that your wireless totally melts down under load. I've attempted a couple of mystery hunts (http://en.wikipedia.org/wiki/Mystery_Hunt) with ~50 clients on one access point and can vouch that that's above the workable capacity of even consumer-grade access points. (We had a fancy commercial grade access point this year with 10s of compact antennas and it did much better.) As Chris noted, we did testing at OLPC and found that even 30 clients was pushing for most access points. At the time, I backed that up with a literature search and could cite the various parts of the 802.11 collision-avoidance algorithm which melted down in the 10s of clients. I can't cite chapter and verse any more, sadly. --scott -- ( http://cscott.net/ ) ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: [Server-devel] [Olpc-open] [IAEP] Sharing EToys projects
On 07.12.2009, at 12:54, Dave Bauer dave.ba...@gmail.com wrote: On Sun, Dec 6, 2009 at 7:22 PM, Gerald Ardito gerald.ard...@gmail.com wrote: Tomeu, There is no mime type that I can see. The Journal entry simply says File filename.pr from url for file. This is no different, by the way, when I upload and then download games we made in Memorize. However, Memorize will load the downloaded game. Thanks. Gerald Hi, I checked the apache config and added the mime type for the .pr files. I downloaded the file on my Mac and it got the correct mime type and offered to open the project in Squeak. I tried on soas-strawberry and XO-802 and it did not open etoys from the journal. Maybe etoys is looking for a different mime-type than x- application/squeak-project? Dave It's supposed to be application/x-squeak-project, not what you wrote above. - Bert - On Sun, Dec 6, 2009 at 7:08 PM, Tomeu Vizoso to...@sugarlabs.org wrote: On Sun, Dec 6, 2009 at 21:31, Gerald Ardito gerald.ard...@gmail.com wrote: Hello. I am working with 140 5th grade students who are using XOs (mostly) and netbooks with SOAS. About 50 of them are using Etoys to create projects. I am trying to find a way to share them with their teachers and each other. When I try to upload them to a Moodle course and them download them, the downloaded files can't be read by EToys. Any ideas? This uses to be a problem with the mime types. Can you see with which mimetype is downloaded the file from moodle? Regards, Tomeu -- «Sugar Labs is anyone who participates in improving and using Sugar. What Sugar Labs does is determined by the participants.» - David Farning ___ IAEP -- It's An Education Project (not a laptop project!) i...@lists.sugarlabs.org http://lists.sugarlabs.org/listinfo/iaep -- Dave Bauer d...@solutiongrove.com http://www.solutiongrove.com ___ Olpc-open mailing list olpc-o...@lists.laptop.org http://lists.laptop.org/listinfo/olpc-open ___ Server-devel mailing list Server-devel@lists.laptop.org http://lists.laptop.org/listinfo/server-devel
