I’m having some issues replicating my breadboard circuit on a PCB. The issue appears to be surrounding the MCP4131 chip (digital potentiometer) that I am using to calibrate a strain gauge bridge circuit.
On the breadboard circuit, I am able to adjust the voltage values (confirmed with DMM measurements of TP7). When I measure TP7 on the PCB, the voltage does not change to changing the register values (always stuck at 2.12V).
Any thoughts on what the root cause could be would be appreciated!
- When I power reset the PCB and load a Blink code, the voltage at TP7 is closer to 1.5V. Whenever I upload any code to the register value (as attached) the TP7 voltage goes to 2.12 V
- I got a colleague to take a look and they mentioned that the CS signal (Pin 6) was not going high after transmission after measuring on an oscilloscope. I didn’t supervise this measurement though, so I am not sure if it’s related. He may have uploaded a different code, different measurement, etc. I attached a screenshot of the oscilloscope reading.
Schematic, Code attached.
Using Arduino Nano IoT
Using the DFN package of MCP4131 on the PCB; DIP package on the breadboard
ArduinoMCP4131Test.ino (663 Bytes)
Schematic_V1_0503.pdf (65.5 KB)
Schematic_V1_Markup.pdf (85.4 KB)