AD7794 test produces no serial output

Troubleshooting
1

Hi, I’m untrained and inexperienced writing code but I’m trying to get my Electron running 0.7.0 OS to talk to an AD7794 via Serial Port 0. The f/w flashes fine but on Reset I get nothing on the terminal. When I flash Tinker or Blink an LED it works fine. I’m guessing the issue is with my code. Is there something obvious I’m missing. I’m using a Library I found on Github [https://github.com/jjuliano77/JJ_AD7794] and i modeled my code after their example. Thanks!


#include "JJ_AD7794.h"

#define AD7794_CS A2
#define SENSOR_EXCITATION A0
#define SPI_RATE 1000000
#define ADC_CHANNELS 6
#define REF_VOLTAGE 3.30

AD7794 adc(AD7794_CS, SPI_RATE, REF_VOLTAGE);

float readings[6]; // 6 channels

void setup() {
    
    Serial.begin(115200);

    pinMode(SENSOR_EXCITATION, OUTPUT);
    digitalWrite(SENSOR_EXCITATION, LOW); // Excitation Off
    
    adc.begin();
    delay(100);
    
    adc.setUpdateRate(470);
    
    for(int i=0; i < ADC_CHANNELS; i++){
        adc.setBipolar(i, true);
        adc.setGain(i, 128);
        adc.setEnabled(i, true);
    }
    
    delay(100);
    
    double junk = adc.read(0);
    delay (10); 
    
    adc.zero();
    
    Serial.println("AD7794");
    Serial.println("time [ms] , Channel, AD7794 value");

}

void loop() {
    
    digitalWrite(SENSOR_EXCITATION, HIGH);
    delay(1000); //mic94063 needs 800 uS to settle
    adc.read(readings, ADC_CHANNELS);
    digitalWrite(SENSOR_EXCITATION, LOW);
    
    Serial.printf("%lu, 1, %i\n\r", millis(), readings[0]);
    Serial.printf("%lu, 2, %i\n\r", millis(), readings[1]);
    Serial.printf("%lu, 3, %i\n\r", millis(), readings[2]);
    Serial.printf("%lu, 4, %i\n\r", millis(), readings[3]);
    Serial.printf("%lu, 5, %i\n\r", millis(), readings[4]);
    Serial.printf("%lu, 6, %i\n\r", millis(), readings[5]);

}
2

What do you mean with "Serial Port 0"?
How have you wired the AD7794?

In your AD7794::begin() function you call SPI.begin() without providing the CS pin. When using A2 as CS this won't make a lot of difference, but when opting for an alternative, that won't work since CS won't be set as OUTPUT then.

3

The AD7794 is connected to Electron on A5-A2 (I called it SPI 0 - better to call it the default SPI). The nets are: A5->DIN, A4->DOUT, A3->SCLK, A2->CS. I verified the AD7794 is getting 3.3V power on DVDD and AVDD.

I realized the SPI bus the AD7794 is on is shared with another IC (a flash memory chip). I did not set that CS pin state in my code (it is on B0). I’m guessing that is a mistake. Should I set that pin as Output, High?