My team and I are using two ADS1298s with TQFP packages for an EMG application. All negative differential pins are tied to ground and the ADCs were both soldered by hand.
Our C program (using a pic24fj128ga204 uC) is designed to send a write command to set register values (all channels), then read back the register values to verify that the registers were set successfully.
When we checked our register read back values (attempted to write (0x91), we noticed that channels 5-8 on our first ADC would only read back (0x00 NUL). When we attempted to write specifically to those registers (button press trigger with different values), the returned value is still 0x00. All other registers matched what was sent. The second ADC functions as intended.
Replacing the ADS1298 did not fix the issue. the same channel registers would still return 0x00. All PCB connections are identical to the functioning ADC #2 (bypass capacitors, voltage pins). I have attached the Altium schematics for the ADC that is not functioning (Labeled U1) and the working ADC (Labeled U2).
If anyone would be able to give insight why these specific channels are not functioning, it would be greatly appreciated. Thank you in advance.