Hello FC community, Time for yet another status update:
* In terms of priority, my current highest one is getting the next batch of 12 FCDEV3B boards assembled. As I already mentioned, I have decided to *not* wait for the resolution of the sleep mode hw bug, i.e., not block the assembly of the next batch of boards until this issue is resolved, thus unless some miracle happens, these next boards will most likely also suffer from the sleep mode bug, and sleep will need to be disabled for reliable operation - I will ship those boards out with a firmware image that has sleep disabled by default. Running with sleep modes disabled should be perfectly acceptable for all of the major uses for which the FCDEV3B is intended, where it is powered from a supply that ultimately takes the power from AC mains, as opposed to truly mobile operation on a battery: given the form factor and interface requirements of these boards (the need for control from a computer), it is difficult for me to imagine how someone could use one of these boards in a truly mobile application where battery life and thus sleep modes would matter. It should be possible to run the FCDEV3B on a battery, connected to a laptop that also runs on its battery, to test mobile functionality like cell reselection, location updates and handover, but such tests are expected to last hours, not days, thus once again the higher battery draw in idle mode due to not working sleep modes should not be a real issue. * Investigating the sleep mode hw bug and doing everything we can to try to fix it is still on the agenda, but it is something I plan on working on after we make the next batch of boards, not before. Based on this reasoning, my plan to buy my own oscilloscope for my home lab is still on, but in terms of allocation of my personal funds it will once again be after the assembly of the next batch of 12 boards. I plan on covering the assembly cost of this next batch (probably somewhere around $1200 USD, assuming that Technotronix charge me the same per-board price as on the previous batch) with my own funds: I still owe boards to a couple of people who have contributed to the initial crowdfunding campaign, so I am not going to ask anyone for any more money until I fulfill those obligations, which I plan on doing from this next batch. * The only issues that remain to be resolved before I give the go-ahead to Technotronix to assemble the next batch of boards are the on-board loudspeaker and microphone circuits. The next step on this front is that I need to have the J312 two-post header desoldered from one of my current test boards and to have the wires from the speaker soldered in its place. I may need to make a trip to Technotronix for this rework, or I might be able to convince the lab technician at my day job to help me. Once the loudspeaker is connected reliably, I will do one more round of loudness tests and will most likely end up needing to up a pair of 0402 resistors from 10 kOhm to 18 kOhm to increase the gain of the amplifier. The needed 18 kOhm resistors are on order from Digi-Key. * The microphone circuit has not been tested at all yet, as I am focusing on the loudspeaker first. If the loudspeaker works but the microphone does not, I may go ahead with the next batch of boards anyway and tell people who need voice input functionality to use the external digital voice interface (MCSI) for it. * Speaking of MCSI, *after* I assemble the next batch of boards and buy my own oscilloscope, I am going to use that scope to determine empirically whether our Calypso DSP puts MCSI into master or slave mode when commanded into what TI called the "Bluetooth headset" mode. Once we know whether it is master or slave (the critical piece of knowledge needed before anything else can be done), I plan on getting one of the readily available and inexpensive FPGA boards, connecting it to the MCSI signals on our FCDEV3B, and building a demo project on that FPGA board that proves a working digital audio interface to our FreeCalypso modem. * Once I get my own o'scope and get back to the investigation of the sleep mode hw bug, a very important avenue of investigation will be comparing the scope-observed behaviour at various test points on our FCDEV3B against an Openmoko-made GTA02, which is essentially the same hw, but does NOT exhibit the bug. Toward that end, I performed a very important experiment last night: on the bare GTA02 I have which I have powered from a bench supply via alligator clips on the battery connector, I have reflashed the firmware to our own FC Magnetite which can take AT commands over RVTMUX (over the external headset jack), inserted a SIM into the socket on that bare GTA02 MB (the exact same SIM with which AT+CFUN=1 causes a self-reboot on FCDEV3B boards with small sleep enabled), and confirmed that the same AT+CFUN=1 command succeeds on this bare GTA02 MB with all sleep modes enabled. This confirmation is important because it disproves the hypothesis (proposed to me off-list) that the problem is with us using a long wire connection to an external power supply instead of a directly attached battery. * In other news not directly related to the FCDEV3B, I finally got the main signal generator on my CMU200 repaired. The replacement Rx/Tx module I bought on ebay arrived in my hands on Monday, I swapped it into my CMU200, and was very delighted to see that my suspicion that the fault was in the Rx/Tx module proved correct: as soon as I swapped that Rx/Tx module out, the signal levels on the internal output from this module became sensible (around 0 dBm when the configured Tx power level is the respective maximum for each external RF port), and once I reconnected the rigid coax piece that takes this internal Tx output to the RF front end, the internal loopback test which failed before started passing. I now need to finish putting this CMU200 back together (the unit came with two of the internal Phillips-head screws way overtightened, the removal of these overtightened screws resulted in their heads being stripped, so I need to replace these two screws with new ones), and when I get the next batch of boards assembled, I will be able to immediately put them through the fully automated procedure for the full RF Rx and Tx test and calibration for all 3 bands. * Finally, other project news going beyond the current FCDEV3B: yesterday I received the BenQ M32 GSM+GPRS modem modules from China about which I posted earlier, and popped one of them open to see the insides. The findings are: there is indeed a Calypso DBB chip and a Iota ABB chip inside like I suspected, but: * The Calypso chip version is D751774AZHH, and according to the TI docs we have, it has DSP ROM version 34. In contrast, the Calypso chip versions we work with have DSP ROM version 36, and this latter version is the only one for which we have known-good, gamble-free L1 support. * The RF block is not Rita or Clara, but implemented with chips from some vendor other than TI - might be Silabs, as the chip markings begin with the letters "SI". TI naturally wanted cellphone and modem manufs to use their RF chips, but the interface between the baseband and RF parts of a GSM modem (when the two aren't in the same chip like they are with newer stuff) is plain analog I&Q and does not leave a lot of room for vendor incompatibility, thus if some cellphone or modem manuf wanted to use RF chips from someone other than TI, but still use TI's baseband chips, TI were happy to sell them the latter. Because of these differences, running our own FreeCalypso firmware on the existing historical M32 hardware from BenQ/ebay will NOT be possible: one might be able to take a gamble with the DSP difference, but the non-TI RF is an absolute show-stopper. However, putting replacement fw on the existing BenQ M32 modules was never my primary interest (it might have made a fun exercise if it were possible, but it is something we can quite easily live without), instead my idea was and still remains to make our own FreeCalypso modem module in the same form factor as the M32, i.e., make our own semi-clone of BenQ's modem, using our version of the Calypso+RF chipset and naturally running our FreeCalypso fw. The good news with the latter plan is that the floorplan of BenQ's little module (the basic arrangement in which the components are laid out) makes good sense, with an internal partitioning wall between the baseband and RF sections like in all of the phones we've been hacking on. The layout of the components on the baseband side of the wall looks good, the Calypso and Iota chip footprints naturally stay the same no matter whose board it is; BenQ used separate flash and XRAM chips, we can either copy the same ones, or we can probably fit our combined flash+RAM MCP footprint into the same space. On the RF side of the internal wall I was very pleased to see that even though BenQ used non-TI chips, the relative placement arrangement of the RF transceiver, the PA, the antenna switch and the Rx SAW filters follows exactly the same general pattern as TI's Leonardo layout, thus we should be able to not only fit a Rita-based RF block in that space, but also make it quadband! Now the catch is that the potential project of making a FreeCalypso modem module in BenQ's form factor will only happen if someone funds it - I am not interested in doing it as an at-risk venture with my own money on the hope that the product sells afterward, instead if this proposed idea is to happen for real, someone will need to fund it upfront. A while back when we were still raising money for the FCDEV3B someone contacted me with an expressed interest in buying FreeCalypso modems in a quantity of 1000 or more pieces, and possibly repackaged in a form factor that is more like SIM900 modules - my current proposal is pretty close to that idea - once we get past building the next batch of FCDEV3B boards with everything working except sleep modes, I am going to reach out to that person once more to see if they are still interested. That's all from me for now. I am now off to get the replacement screws for putting my CMU200 back together, and after that I will be looking for local assistance with the loudspeaker soldering rework. Hasta la Victoria, Siempre, Mychaela aka The Mother _______________________________________________ Community mailing list Community@freecalypso.org https://www.freecalypso.org/mailman/listinfo/community