How do I set parameters on the ADC of my Seeeduino LoRAWAN arduino board? I am trying to get as much precision as I can for my measurements and understand that I can set a number of constants to change the ADC operation.
I have the Atmel AT07627: ASF Manual (SAM D21), which gives enumerations for ADC settings but apparently I can’t just slap their code into the Arduino IDE because it doesn’t recognize the data objects.
I have seen some code examples that use things like:
I want to use the Arduino IDE. I hope I don’t need to deal with ASF, but I haven’t been successful in addressing the ADC chip. I thought I could use the structures ATM had defined in their documentation but that doesn’t seem to work and I haven’t been successful using the “ADC->” form either. Here is a cut-down version of my code that I am using for testing.
/*Code to read a Teros 10 capacitance soil moisture sensor, output reading to Serial
* All LoRaWAN code removed for debugging
* Written for Seeeduino so the serial port to the computer is SerialUSB
* The current requirement of the sensor is 12 mA at 3VDC so can power from digital pin
*/
// millis timer global------------------------------------------------------------------
#include <millisDelay.h> //handy timing library
//https://www.forward.com.au/pfod/ArduinoProgramming/TimingDelaysInArduino.html
millisDelay SensorDelay; // the delay object
// battery of Seeeduino LoRaWAN
const short pin_battery_status = A5;
const short pin_battery_voltage = A4; //note that this will read the USB voltage if plugged into computer
boolean arStatus; //not very useful
int arVoltage;
float bvoltage;
const int Apin = A3; //analog pin connected to sensor +
const int ReadingTime = 20; //time to read from Apin in ms 10 is minimum
int SensorBits = 0; //variable to store sensor reading from 12 bit A/D converter
double SensorMV = 0; //store sensor reading converted to mV
// Setup readings global-----------------------------------------------------------
const unsigned long DelayTime = 1000*60; // have const here so it is easy to find and change (in mS)
// end global----------------------------------------------------------------------
void setup() {
// put your setup code here, to run once:
pinMode(Apin, INPUT);
pinMode(LED_BUILTIN, OUTPUT); //During testing have the LED on when taking a reading
SerialUSB.begin(19200);
while (!SerialUSB) {
; // wait for serial port to connect
}
//analogReadResolution(12); //will do this through direct addressing
//analogReference(AR_INTERNAL); //2.23V SAMD Boards e.g. Zero/Seeeduino only has error
//Read sensor once as throwaway value but print it out
SerialUSB.println("Read in setup");
digitalWrite(LED_BUILTIN, HIGH);
delay(10);
SensorBits = analogRead(Apin);
digitalWrite(LED_BUILTIN, LOW);
SerialUSB.print("SensorBits = ");
SerialUSB.println(SensorBits);
SensorMV = SensorBits/4096.0*3.3; //Not sure if this should be 4095. Assumes 3.3 mV analog reference
SerialUSB.print("SensorMV = ");
SerialUSB.println(SensorMV);
//Read sensor again after setting to 12 bit for testing as throwaway value but print it out
SerialUSB.println("Set ADC to 12 Bit using direct addressing");
configure_adc();
digitalWrite(LED_BUILTIN, HIGH);
delay(10);
SensorBits = analogRead(Apin);
digitalWrite(LED_BUILTIN, LOW);
SerialUSB.print("SensorBits = ");
SerialUSB.println(SensorBits);
SensorMV = SensorBits/4096.0*3.3; //Not sure if this should be 4095. Assumes 3.3 mV analog reference
SerialUSB.print("SensorMV = ");
SerialUSB.println(SensorMV);
SensorDelay.start(DelayTime); //Start millis delay timer for sensor reading intervals
} //end setup
void loop() {
// put your main code here, to run repeatedly:
if (SensorDelay.justFinished()) { // repeat delay and take reading
SensorDelay.repeat(); // repeat
SerialUSB.print("millis() = ");
SerialUSB.println(millis());
ReadTeros10();
// SendPayload();
}
} //end loop
void configure_adc(void){
/* This routine uses commands that send instructions directly to the SAM-D21 chip
* so it is not portable to other systems
* they are taken from the AT07627: ASF Manual (SAM D21)
* not sure which commands are needed so trial and error
*/
ADC->ADC_ACCUMULATE_SAMPLES=ADC_ACCUMULATE_SAMPLES_16;
} //end configure_adc
void ReadTeros10() {
digitalWrite(LED_BUILTIN, HIGH);
delay(10);
SensorBits = analogRead(Apin);
digitalWrite(LED_BUILTIN, LOW);
SerialUSB.print("SensorBits = ");
SerialUSB.println(SensorBits);
SensorMV = SensorBits/4096.0*3.3; //Not sure if this should be 4095. Assumes 3.3 mV analog reference
SerialUSB.print("SensorMV = ");
SerialUSB.println(SensorMV);
} //end ReadTeros10
