How to fix ADS129x RLD output being stuck at AVDD
I wanted to use my ADS1291’s Right Leg Drive amplifier to output the internal midsupply. I’ve spent several hours trying to figure out why it was stuck at AVDD. Spoiler alert: my configuration was incorrect.
This post was written and tested using and ADS1291, but in principle it is relevant for all the 1/2 channel ADS1x9x devices:
- ADS1191
- ADS1192
- ADS1291
- ADS1292
- ADS1292R
If you are using an ADS1x9x device and your RLD output voltage is stuck to AVDD, try reviewing the register values you are configuring.
I’ve stumbled upon this post while debugging this issue. While unhelpful for me, it showed that some people were indeed having the same issue as I. And in this comment we can see the cause of the issue:
;ADS129x_RESP1 , #000000000B ; data: resp off (default))
The default value of the RESP1 register should be 0x02, or 00000010b. In the datasheet bit 1 is “Must be set to ‘1’”.
After fixing this, the Right Leg Drive output changed to the expected value.
Lessons learnt: triple check the register default values.