ADS131M08: SPI Problems Persist (we are on a Raspberry Pi 4 model B)

Hi Clark,

I checked your timing:

1. During the first 50ms period in your timing, you forced /SYNC/RESET signal to low when you were sending SCLKs and /CS to the ADC, and also you were sending 16 SCLKs to the ADC, but the default word length is 24 bits, those operations are definitely wrong.
2. Starting from 5.9ms in your timing, you sent 20 bytes SCLKs to the ADC in one frame, then went back to 2 bytes (16 SCLKs), then you repeated this sequence between 20bytes and 2 bytes as a frame.
3. Starting from 53.5ms until 58.8ms, you forced the /SYNC/RESET signal to high, but there are a lot of spikes on the /CS, those spikes definitely messed up the communication between the ADC and your host controller.
4. After the moment of 58.8ms, you timing went back to 2 bytes (16 SCLKs), you received 0x05FF data on MISO, this is the correct response from the ADS131M08 ADC, this is the STATUS word.

I double checked the photograph of your test setup in your previous post from the link, you are using so many blue wires and also a bread board to connect the digital SPI and control signals from the ADC EVM board to your host controller board, so I'm not surprised spikes were seen on your /CS signal. I would strongly recommend you:

• Design a circuit board to combine both your controller and the ADC device to a single circuit board or use short blue wires between the EVM and your controller board without a bread board.
• Correct your software code and optimize your timing, I already showed my timing in your previous post that can be a reference for you.

BR,

Dale

Hi Clark,

Thank you for your update. Let me know if you have any further questions.

BR,

Dale

Hi Clark,

Thanks for your update. 

BR,

Dale