Is there anything that could be done to improve the driving capability of the i2c devices ?
Out of interest is the DS2482-100 any better, it would of course be possible have multiple ones of these on the same i2c bus. Stuart On 23/04/12 11:50, Achim Scheidl wrote: > Don't forget, that the I²C bus-master can drive much less capacity load on > cable (I measured a max of only 8,9nF which represent about 89m IY(ST)Y > cable) > The USB bus-master based with DS9490R is able to drive 28nF - so > theoretically about 280m cable > > On Mon, Apr 23, 2012 at 11:25, Chris Lautre <chris.lau...@karusoft.com>wrote: > >> I would be very interested in a USB to 1Wire Hub with 8 1 Wire ports. >> This would eb much better than using multiple DS9490R. >> >> Chris >> >> >> On 22/04/2012 10:42, Patryk wrote: >>> I propose a new USB 1-wire adapter. >>> The DS2490 native USB 1-wire adapter is no longer in production. I think >>> you can still buy built adapters from Hobbyboards but if You want to >> build >>> your own it's nearly impossible to source this chip. The popular solution >>> is to use DS2480B with some serial to USB converter like FT232 it behaves >>> then like native DS2490. However if one plans to have w big 1-wire >>> network with multiple branches the better way seems be DS2482-800 which >> is >>> basically a 1-wire master with one bus connected to a 8 port hub. You >> can >>> have then a star topology. Again You can still(not sure) buy a hub from >>> Hobbyborad to achieve the same goal but the hub chip is also out of >>> production. So if you are familiar with soldering iron this is a solution >>> for you. >>> >>> The DS2482-800 uses I2C bus. The conversion form I2C to USB is handled by >>> Atmega8A which is a 8 bit microcontroller and runs a special program. >>> It's a very popular chip it costs about $2(at least in Poland). However >>> You have to upload the firmware to it for which you need a programmer. If >>> you don't have one but you have an old PC with parallel port you can >> build >>> one with few resistors and a plug. Also Raspberry Pi can program AVR >> chips. >>> First I run i2c-tiny-usb >>> http://www.harbaum.org/till/i2c_tiny_usb/index.shtml on Atmega8 >>> but there was a performance issue. The read from DS18B20 took about 3 >>> seconds >>> and without specifying the bus about 10. Compared to 1.5 with DS2480 and >>> similar >>> time connected to vga i2c port. >>> Fortunately there is a derivative project from Till's i2-usb-tiny it's >>> called OSFI(Open Source InterFace) . It's part of a project called >>> OpenServo http://www.openservo.com/StepByStep >>> It uses Atemga8 and has better performance because it uses some built in >>> i2c(do not know exactly). >>> >>> Here is the whole circuit. I think it's pretty explanatory. For testing >>> You can omit the voltage regulator and power it directly from USB and not >>> using the diodes should be fine for most computers. I done my prototype >> on >>> a breadboard and it works fine. >>> http://ubuntuone.com/6uM1yQRB36zgGEFDxrTc7c >>> >>> >>> On the 1-wire side DS9503 are not essential to get it running they just >>> protect the bus from electrostatic discharges. However they are cheap. I >>> used RJ-12 connectors (telephone) There are different standard's of >> wiring >>> the additional +5V the RJ45 are also popular. You can use screw >> connectors >>> as well. I think I will use 4 RJ45 for longer cables and if more power is >>> needed and RJ12 for thermometers. >>> >>> After assembling it on a breadboard You have to program the uC the >>> firmware can be downloaded from OpenServo cvs. >>> >> http://www.openservo.com/viewcvs/OpenServo/Interfaces/OpenServo_InterFace/driver/Version_2/firmware/?root=cvs >>> You need main.hex >>> avrdude -c usbasp -p atmega8 -U lfuse:w:0x9f:m -U hfuse:w:0xc9:m -U >>> flash:w:main.hex >>> >>> Then you can test if it's recognized by the system >>> lsusb shows >>> Bus 001 Device 005: ID 1964:0001 >>> There is no name for it >>> >>> Then you have to compile kernel module >>> >> http://www.openservo.com/viewcvs/OpenServo/Interfaces/OpenServo_InterFace/driver/Version_2/kernel/?root=cvs >>> make >>> sudo make install >>> sudo depmod -a >>> >>> sudo modprobe osif >>> >>> sudo modprobe i2c-dev >>> >>> then >>> sudo i2cdetect -l >>> should show something like this >>> i2c-0 i2c OSIF at bus 001 device 005 I2C adapter >>> >>> Then you can run owfs >>> sudo owfs –i2c=/dev/i2c-0 /mnt/owfs >>> You can also use the parameter >>> --i2c=ALL:ALL and owfs will look at every i2c device. However there is >>> some bug in older version an you might get segmentation fault. It is now >>> fixed in CVS >>> >>> The you should get something like this >>> sudo ls /mnt/owfs >>> bus.0 >>> bus.1 >>> bus.2 >>> bus.3 >>> bus.4 >>> bus.5 >>> bus.6 >>> bus.7 >>> settings >>> structure >>> uncached >>> statistics >>> system >>> >>> Here's the whole Eagle project the board is half done >>> http://ubuntuone.com/32tUJtqRyNr3ngTsApwW83 >>> and how it looks like on a breadboard >>> http://ubuntuone.com/0CUuACUSJMW69aK2FznM6i >>> >>> >>> Pleas give tips how to improve this tutorial. The board is on the way. >>> >> >> ------------------------------------------------------------------------------ >> For Developers, A Lot Can Happen In A Second. >> Boundary is the first to Know...and Tell You. >> Monitor Your Applications in Ultra-Fine Resolution. Try it FREE! >> http://p.sf.net/sfu/Boundary-d2dvs2 >> _______________________________________________ >> Owfs-developers mailing list >> Owfs-developers@lists.sourceforge.net >> https://lists.sourceforge.net/lists/listinfo/owfs-developers >> > > > ------------------------------------------------------------------------------ > For Developers, A Lot Can Happen In A Second. > Boundary is the first to Know...and Tell You. > Monitor Your Applications in Ultra-Fine Resolution. Try it FREE! > http://p.sf.net/sfu/Boundary-d2dvs2 > > > _______________________________________________ > Owfs-developers mailing list > Owfs-developers@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/owfs-developers ------------------------------------------------------------------------------ For Developers, A Lot Can Happen In A Second. Boundary is the first to Know...and Tell You. Monitor Your Applications in Ultra-Fine Resolution. Try it FREE! http://p.sf.net/sfu/Boundary-d2dvs2 _______________________________________________ Owfs-developers mailing list Owfs-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/owfs-developers