I2C With Fan Hat

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Nate N

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May 10, 2021, 8:06:20 PM5/10/21
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Has anyone figured out how to work other I2C devices (particularly hats) with the Clusterhat aboard a Pi 3B+?
I'm trying to use the Argon 40 fan hat for my Pi. It uses the I2C to control fan speed and the Pi's shutdown and reboot modes. The Clusterhat works perfectly well plugged in and the fan works perfectly well plugged in. However, when I plug both in (Pi on Bottom -> Fan Hat -> Cluster on Top), the Clusterhat won't respond. I've used jumpers to make the connection between the two hats, but it still wouldn't work.
The blue LED and red LED stay lit (blue is dim). But I can't control the zeros and the Hat isn't seen by my 3B+ at all.
From my experience with Arduino, I'm under the impression that there can be multiple devices on the I2C bus as long as they have separate IDs.

Chris Burton

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May 11, 2021, 2:11:25 AM5/11/21
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Hi,
If the Argon 40 fan HAT follows the HAT spec then it will have a HAT EEPROM (which it looks to have) so both HAT will have an HAT EEPROM on the same I2C address.

I'd start by setting CLUSTERHAT_FORCE in /etc/default/clusterctrl to the version of ClusterHAT you have and if you have a ClusterHAT v2.5 you can also cut the ID_SCL / ID_SDA solder jumpers on the back of the board to disconnect the HAT EEPROM so there's less chance of it causing issues with the other EEPROM.

Chris.
 

Nate N

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May 11, 2021, 9:41:25 PM5/11/21
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Thank you for the response! How would that affect the HAT and cluster? Does it limit any other functions or would it not do anything? I want to make sure before I start cutting jumpers! Would turning the EEPROM write protect on/off help this problem as well without any physical changes to the board?

Chris Burton

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May 12, 2021, 7:20:21 AM5/12/21
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Hi,
Thank you for the response! How would that affect the HAT and cluster? Does it limit any other functions or would it not do anything? I want to make sure before I start cutting jumpers! Would turning the EEPROM write protect on/off help this problem as well without any physical changes to the board?

Editing the file just overrides the fact if can't find the ClusterHAT HAT EEPROM and it carries on as though it can with the version you've specified.

Cutting the solder jumper just disconnects the EEPROM so you won't have 2 EEPROM on the same I2C address. If you want to use it at a later date in a different setup you'd need to either edit the config file again or bridge the solder jumpers to restore it back to normal operation.

Chris.

David Glaude

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May 12, 2021, 12:56:34 PM5/12/21
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Maybe you should promote you Butterfly solution: https://www.tindie.com/products/8086net/butterfly/
You can have one board that has the ID I2C and the other that is not connected.

Just saying...

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Nate N

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May 12, 2021, 5:42:56 PM5/12/21
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It works, I can work the nodes and keep the Pi nice and cool! :) It took a second to realize that I needed to take out the description part of the values but I got that! Just to make sure everything is normal, I can connect to the nodes via the terminal and control the board, but I can't use the ClusterCTRL window with the sliders to turn the nodes on and off. That's normal since the EEPROM is disabled right?
Thank you for the help!

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