Hello! Just ordered a Replicape and I'm trying to test some of the electronics

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Hello! Just ordered a Replicape and I’m trying to test some of the electronics I have on hand before it arrives. I have a MAX31820PARMCR+ sensor, which is a One-Wire temp sensor from MAXIM and I am trying to make it work with my Beaglebone (I have a BB Green Wireless). The BB is running Kamikaze. The problem is that I cannot see the sensor when running “ls /sys/bus/w1/devices/”. One reason might be that the sensor only supports parasitic-power mode, where it sucks power from the DQ line, which the driver does not account for.

I cannot find where the one-wire protocol is implemented in the Kamikaze distribution - it seems that most standard tutorials on how to run one-wire on BB either presume that the device will be listed in “/sys/devices/w1_bus_master1” (link to tutorial: http://www.bonebrews.com/temperature-monitoring-with-the-ds18b20-on-a-beaglebone-black/) or that there exists a file “/sys/devices/bone_capemgr.9/slots” (for example this tutorial: https://interactingobjects.com/ds18b20-temperature-sensor-on-a-beaglebone-black-running-ubuntu/). Neither of these seem to correspond with what is running on my Kamikaze BB (the folders do not even exist). Also when I rum lsmod, there is no w1-gpio nor w1-therm as suggested by some of the tutorials.

So how is the one-wire implemented? How can I modify it? Any suggestions on getting this working?

Thanks,
Matouš

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tl;dr:
So again - where do I find the OneWire driver and how do I modify it?

So I delved a bit deeper into the Device tree setup on the Kamikaze and it turns out that for some reason instead of the standard path “/sys/devices/bone_capemgr.9/slots” the slots file is located in
“/sys/devices/platform/bone_capemgr/” for some reason. There is also a file “BB-W1-P9.12-00A0.dtbo” board file located in “/lib/firmware/”, so I loaded it by running “echo BB-W1-P9.12 > /sys/devices/platform/bone_capemgr/slots” and it successfully created the slot and a device in “/sys/bus/w1/devices/” called “w1_bus_master1”. So it seems to be working somehow. But no device for the sensor connected to my board appears, only some garbage with nonsense names like “00-4000000” etc., which would point at the sensor not communicating properly, but still trying to do so. I have tried connecting the sensor to P9.22 as implied by the pinout image (on http://wiki.thing-printer.com/index.php?title=Replicape) as well as P9.12 as implied by the name of the board file and neither worked.

I am suspecting that the OneWire driver itself has to be modified in order to support the parasitic mode properly, but I cannot find it. It has cost me a lot of time to get even this far and I would really appreciate some help or at least some directions.

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This is how it’s done in Redeem: https://bitbucket.org/intelligentagent/redeem/src/0dc7929320eec5f4573579aab4fb31ddaab8bbbd/redeem/Redeem.py?at=master&fileviewer=file-view-default#Redeem.py-258

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From memory, I think only DS18B20 has been tested, but it should give a starting point. Realy simple code for those.

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Thanks for your answer, the code you linked to will certainly be useful. However I think that I will have to look into the linux onewire driver itself. I found some forum threads discussing onewire with parasitic mode on the RasPi and they got it working but is seems that Kamikaze uses a different version of the driver.