We're seeing the weirdest thing with our AD7124-8SDZ evaluation boards when measuring PT100 RTDs. I've tested 3 of our boards and they all read incorrect voltage measurements for an RTD connected to AIN2-7. I used a single PT100 and tested each analog pin individually and produced the following measurements:
AIN0 - 0.0553 V
AIN1 - 0.0553 V
AIN2 - 0.549 V
AIN3 - 0.549 V
AIN4 - 0.546 V
AIN6 - 0.551 V
AIN7 - 0.551 V
AIN8 - AIN15 all read 0.0555 V (which is equivalent to about 110 ohms for PT100s at room temperature, so great measurements). Also completed the tests with a 2N2222 transistor RTD and saw the same behavior. I saw the same behavior on all 3 boards I tested and don't understand why those analog pins would be different from the rest.
My configuration also looks to be fine:
IO_CONTROL = [0x03, 0x00, 0x04, 0x0Y] //where Y = 0,1,2,3 ... F for AIN0 ... AIN15
Channel_0 = [0x09, 0x80|(Y>>3), 0x05|(Y<<5 & 0xFF)] //AINP = same pin in IO_CONTROL, AINM = AIN5
This is my wire setup:
(Where I have all of the default jumpers (LK x) set other than LK5 for noise test on AIN0/AIN1.)
I've posted quite a bit in just these past few months with questions. Thank you so much for your continuing help!