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. -- p4trykx ------------------------------------------------------------------------------ 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
