4-20mA R click calibration

receiver_calibration.ino

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Project name:
Project page: https://electronza.com/4-20ma-current-loop-revisited-a-simpler-calibration-procedure
Description:  
********************************************************************/


/*
  4-20mA R click calibration
  Reads result on 4-20mA bus and outputs the
  result of the conversion on serial monitor
 */
#include <SPI.h>
 
// Arduino UNO with Mikroe Arduino Uno Click shield
// 4-20mA R click is placed in socket #2
// CS   is pin 9
// SCK  is pin 13
// MISO is pin 12
// MOSI is pin 11
#define ADC_CS 9
 
unsigned int ADC_result;
float ADC_avrg;
 
void setup() {
/* Resetting MCP3201
 * From MCP3201 datasheet: If the device was powered up
 * with the CS pin low, it must be brought high and back low
 * to initiate communication.
 * The device will begin to sample the analog
 * input on the first rising edge after CS goes low. */
 pinMode (ADC_CS, OUTPUT);
 digitalWrite(ADC_CS, 0);
 delay(100);
 digitalWrite(ADC_CS, 1);
 
 // initialize serial
 Serial.begin(9600);
 // initialize SPI
 SPI.begin();
 
}
 
void loop() {
  ADC_avrg = 0;
  // Average of 100 measurements 
  for (int i=0; i<100; i++){
  // put your main code here, to run repeatedly:
  ADC_result = get_ADC();
  //Serial.print("Conversion result: ");
  //Serial.println(ADC_result);
  // Dont print too often
  delay(10);
  ADC_avrg = ADC_avrg + ADC_result;
  }
  Serial.print("Conversion average: ");
  Serial.println(ADC_avrg / 100);
  delay(500);
}
 
unsigned int get_ADC(void){
/*
DAC works on SPI
We receive 16 bits
Of which we extract only 12 bits
MCP3201 has a strange way of formatting data
with 5 bits in the first byte and
the rest of 7 bits in the second byte
*/
  unsigned int result;
  unsigned int first_byte;
  unsigned int second_byte;
 
  SPI.beginTransaction(SPISettings(1000000, MSBFIRST, SPI_MODE1));
  digitalWrite(ADC_CS, 0);
  first_byte = SPI.transfer(0);
  second_byte = SPI.transfer(0);
  digitalWrite(ADC_CS, 1);
  SPI.endTransaction();
 
  /* After the second eight clocks have been
  sent to the device, the MCU receive register
  will contain the lowest order seven bits and
  the B1 bit repeated as the A/D Converter has begun
  to shift out LSB first data with the extra clock.
  Typical procedure would then call for the lower order
  byte of data to be shifted right by one bit
  to remove the extra B1 bit.
  See MCP3201 datasheet, page 15
  */
  result = ((first_byte & 0x1F) << 8) | second_byte;
  result = result >> 1;
  return result;
}