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1 Wire Pi Plus not detected

54 Views - Created 5 days ago

5 days ago

Posted by:
jfm

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Hi guys,

I installed a 1 Wire Pi Plus on a new Raspberry Pi 4B but it isn't detected by i2cdetect (no device detected).

- The jumper at J1 is in place
- My soldering skills are very limited and it took me ages, but I triple-checked that the soldering is clean, no bridges.
- I2C is enabled on the Pi (via raspi-config and the corresponding line is visible in /boot/config.txt, to which I also added the baudrate and core_freq settings). Duely rebooted, a few times actually.
- 3 DS18S20 sensors on the 1-wire line (soldered to the board)

Any ideas?

Thanks in advance,
JF

4 days ago

Posted by:
andrew

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Location:
United Kingdom

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Hi JF

Do you have a multimeter you could use to measure the 5V and GND pins on the corner next to the RJ12 connector? If 5V is present on those pins that means the 1 Wire Pi should be receiving power. If there is no voltage then there is a connection problem either with the J1 header or the GPIO header.

The most common reason for the 1 Wire Pi not working is a bad solder joint so it may be worth reheating each pin on the GPIO header to make sure the solder has flowed fully around the joint.

If the board still does not work after trying the suggestions above you could try reducing the I2C baud rate down to 100KHz just in case something is stopping it from working at its full speed.  Update the baud rate parameter in /boot/config.txt to "dtparam=i2c_baudrate=100000" and hopefully the 1 Wire Pi will appear on i2cdetect.

AB Electronics UK Tech Support

4 days ago

Posted by:
jfm

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Hi Andrew,

Thanks for the reply. I don't have a multimeter but could connect the 5V port as an input to a relay board with both led and relay. Connecting the 5V GPIO pin to that setup normaly results in a LED turning on and the relay activating.

With the Pi Plus present, I can see there IS some voltage on the 5V port, but very little as the LED on the relay board barely lights up and the relay doesn't activate. Same thing when connecting to the 5V GPIO pin while the Pi Plus is present.

Interestingly, the 3.3V pins on the GPIO go also amiss when the Pi Plus is present: barely connecting a 3.3V pin to the relay input, which normally does nothing else than activating the relay, instead spread havoc on the GPIOs inputs levels (and turned my home into a Christmas tree as I use GPIO inputs to detect button pushes).

I've now removed the Pi Plus to avoid any damage.

Any thoughts? Frankly I wish I could have purchased a pre-soldered board.

Thanks,
JF

 

4 days ago

Posted by:
andrew

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Location:
United Kingdom

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Hi JF

It sounds like you have a short circuit somewhere. On the 1 Wire Pi Plus the only GPIO header pins that are used are the first 6 pins for power and I2C and the various ground pins across the header so if there is a short circuit it is probably between one of those pins.

Is the board aligned correctly on the GPIO header? It should look like the photo below when it is connected to the Raspberry Pi.

1 Wire Pi Plus

AB Electronics UK Tech Support

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