Am 03.09.2016 um 10:36 schrieb Colin Law: > I want to use owserver on a raspberry pi (zero) running Raspbian > (Jessie) using the method of direct connection to GPIO pins with a > pullup resistor. Unfortunately I have found a fair amount of > conflicting and confusing information on this around the web. Is > there an up to date and authoritative write up somewhere on how to do > this? > 1. You have to recall the Raspberry Pi's GPIOs are 3.3V. You'll have a non-standard 3.3V Onewire then. That's okay for the DS18B20, but for other Onewire chips, you have to check the datasheets. Same, if you use an external pullup, it has to go to 3.3V, not 5V.
Of course, you can always use this simple level shifting circuit, should you need a 5V Onewire: | | +5V ----. ,-----+---- +3.3V | | | | | \ G | \ | / –––––' / | \ ––– – ––– \ | | | ^ | | | 5V bus line ---+-----' '--+-----+---- 3.3V bus line | D S | The transistor is a small signal N-channel enhancement mode MOSFET, e.g. a 2N7000, BS170 or MMBF170. The value of the two pullup resistors depend on the pullup current you need, 1.5kΩ is okay for most cases. 2. You have to put dtoverlay=w1-gpio,gpiopin=4 or dtoverlay=w1-gpio-pullup,gpiopin=4,pullup=5 into your Raspberry Pi boot partition config.txt. And of course, the w1-gpio resp. w1-gpio-pullup dtb files have to be present in the boot partition overlays directory. Then reboot. 3. You have to use --w1 for this. The w1 kernel driver is the only way to use the bitbanging host adapter. 4. You have to update your owfs to 3.1p1 or later, because Debian Jessie uses kernel 3.16.x, and there was a long-unseen incompatiblity between post-3.16rc kernels and pre-3.1p1 owfs. You can use the owfs packages from the Raspbian testing repository. Edit (or create) your /etc/apt/preferences to contain: -------------------------------------------------------------------------- Package: * Pin: release o=Raspbian,a=stable Pin-Priority: 500 Package: * Pin: release o=Raspbian,a=testing Pin-Priority: 300 -------------------------------------------------------------------------- This is important so you keep stable (Jessie) for all packages but the ones explicitly taken from testing (Stretch). Then, add a line -------------------------------------------------------------------------- deb http://mirrordirector.raspbian.org/raspbian/ testing main contrib non-free rpi -------------------------------------------------------------------------- to your /etc/apt/sources.list to get access to the Raspbian testing repository. Do an $ sudo apt-get update to read the package metadata, then check $ sudo apt-cache policy whether the testing repo is there with priority 300. Then $ sudo apt-get update -t testing owserver ow-shell That should install all you need, including the startup files and systemd units. Note you have to edit /etc/owfs.conf again to contain (this and only this) -------------------------------------------------------------------------- !server: server = localhost:4304 server: w1 -------------------------------------------------------------------------- Restart the owserver service after that. Done. Kind regards Jan ------------------------------------------------------------------------------ _______________________________________________ Owfs-developers mailing list Owfs-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/owfs-developers
