Correct setup for AD7793?

Hi,

I am evaluating AD7793 through the EVAL-CN0355-PMDZ board. In order to understand how it works I'm using the NO-OS driver found here and trying to interface it with an Arduino, but as far I can see, data is a little bit strange.

When I execute AD7793_Init(), the function does not return 1, it returns 0 meaning the device is not correctly detected.

When I read from the AVDD Monitor with these functions:

  AD7793_SetChannel(AD7793_CH_AVDD_MONITOR);
  unsigned long conv = AD7793_SingleConversion();
  float AVDD = ((conv - 8388608.0) / 8388608.0) * 1.17 / (1/6.0);
It returns a value that oscillates around 4.9V, which seems correct because I'm powering the board with 5V, also when I read the chip temperature I read the ambient temperature, which seems to be correct. The problem comes when I try to read from AIN2, I get data that is absolutely not correct.
AD7793_SetExcitCurrent(AD7793_EN_IXCEN_1mA);
AD7793_SetChannel(AD7793_CH_AIN2P_AIN2M);
conv = AD7793_SingleConversion();  /* Returns the result of a single conversion. */
float Temp = (((conv - 8388608.0) / 8388608.0) * 1.17 * 1000 / 0.810);
First I set the excitation current to 1mA, then I set the channel to read and finally I try to get the conversion. But data read varies from -1444.44 to 1444.44. Data read should be zero because I'm not using an RTD, but a resistance with a nominal value of 100 Ohm (100 Ohm correspond to 0ºC). So I think I'm missing some configuration before getting the data.
Any ideas of what I'm doing wrong?


Formatation done.
[edited by: rnicolas at 3:40 PM (GMT -4) on 17 Mar 2021]