Hello,
This is a follow up question to:
https://e2e.ti.com/support/data-converters-group/data-converters/f/data-converters-forum/1022706/ads124s08-trouble-reading-conversion-data-with-internal-or-external-reference?tisearch=e2e-sitesearch
Since posting the previous thread, I determined that I had a bug in my software preventing the Reference Control Register to be written. Since then I have fixed this bug but am still not able to read valid conversion data. I am running the ADC with the internal reference, differential inputs (Ain2 tied to ground and set as the negative input, Ain9 set as the positive inputs signal and tied to a GPIO signal off the ADC). I have the PGA disabled and the internal reference buffers disabled.
I have a ADC GPIO configured as an output which I have tied to the Ain9 input signal and I toggle it on every conversion reading. Although I would expect to read 0V and 3.3V conversion data based on this GPIO input, I continuously get conversion results that do not match what I expect. Occasionally, I will get results that look like they may be correct but that could just be a coincidence. I am using the slowest data rate of 2.5 SPS for debugging and am polling the DRDY pin for read timing.
Here are some screen shots of my coms:
Initialization (There is a 3.7 ms delay between all initialization commands):
- Reset Command
- Configure System Reg
- Enable Send Status
- Enable CRC
- Configure Input Mux Reg
- Ain2 = negative input
- Ain9 = positive input
- Configure Reference Reg
- Internal reference always on
- Use internal 2.5V reference
- Disable both reference buffers
- Configure GPIO Data Reg
- GPIO 1 = Output
- Set GPIO 1 = high
- Configure GPIO Config Reg
- Set Ain7 as GPIO (GPIO-1)
- Configure Data Rate Reg
- Set to 2.5 SPS
- Read back Reference Reg for debug
- Start Command
Reading Conversion Data:
- Bad low signal reading in through Ain9: Conversion results = 1,550,847
- Bad high signal reading in through Ain9: Conversion results = 6,946,233
- Good low signal reading through Ain9? Conversion results = 124,865
- Good high signal reading though Ain9? Conversion results = 8,388,607
- Overall conversion reads showing timing