RE: SDA/SCL when stacking.
1226 Views - Created 20/01/2020
The best way to wire the ADC boards will be to use the SDA (pin 3) and SCL (pin 5) pins on the GPIO header. That way each I2C bus will be buffered through the voltage level translator on each ADC board and they should all show up with i2cdetect.
You will also need to connect the 3.3V (pin 1), 5V (pin 2) and ground (pin 6) on the GPIO header to the Raspberry Pi.
Are you using the SDA and SCL on the ADC Pi on the board's GPIO connector or the two separate SDA and SCL pins? The pins on the GPIO connector operate at 3V whereas the separate ones are 5V so if you connect them to the Raspberry Pi they will feed 5V back into the Raspberry Pi GPIO header which could damage it. I would recommend only using the pins on the GPIO header to connect to the Raspberry Pi.
The I2C voltage level shifter on the ADC Pi needs 5V and 3.3V to operate correctly so you will need to run a 3.3V wire to the ADC Pi as well for it to work.
I'll do this over the next day or so and let you know if that solves the issue.
If you attach the wires to the top header then it will pass through to the other boards below it and they should all appear on the I2C bus.
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