guess

modulate_ld_spi.c

#include <SPI.h>

// Generated using https://www.daycounter.com/Calculators/Triangle-Wave-Generator-Calculator.phtml
// max value 2^9
// num values 128
// val 0-4096 | mA 0-300
// 
int16_t* pValues = NULL;
int valuesCount = 0;

// Due to ADN8810 output impedance drop off
const int currentChangeFrequecy = 10000;
const int triangleMmodulationFrequency = 520;
const float minCurrent = 0.02335; //23.35 mA
const float maxCurrent = 0.02345; //23.75 mA
const int16_t maxValue12Bit = 4095;
const float maxAmps = 0.3;
const float conversionFactor = maxValue12Bit / maxAmps;

// Assume address 0
bool fillTriangleValues(int modulationPPFrequency, int16_t minValue, int16_t maxValue) {
  int16_t value = 0;
  int16_t step = 0;
  int valuesCount = 0;
  int valuesHalfCount = 0;
  
  if (modulationPPFrequency > currentChangeFrequecy){
    return -1;
  }
  
  if (pValues)
  {
    free(pValues);
    pValues = NULL;
  }
  
  valuesCount = currentChangeFrequecy / modulationPPFrequency;
  valuesHalfCount = valuesCount/2;
  
  pValues = (int16_t*) malloc(valuesCount * sizeof(int16_t));
  if (!pValues) {
    valuesCount = 0;
    return -2;
  }
  
  step = (maxValue - minValue)/valuesHalfCount;
  
  if (minValue < 0) return -3;
  if (maxValue > maxValue12Bit) return -4;
  
  value = minValue;
  for (int i = 0; i < valuesCount; i++)
  {
    int sign = i < valuesHalfCount ? 1 : -1;
    value += step * sign;
    
    value = value > maxValue ? maxValue : value;
    value = value < minValue ? minValue : value;
    
    pValues[i] = value;    
  }
  
  return 0;
}

// using two incompatible SPI devices, A and B. Incompatible means that they need different SPI_MODE
const int slavePin = 4;

// set up the speed, data order and data mode
// modes: https://www.arduino.cc/en/reference/SPI
SPISettings settingsB(currentChangeFrequecy, MSBFIRST, SPI_MODE3);

void setup() {
  if (fillTriangleValues(triangleMmodulationFrequency, ) >= 0)
  {
    // set the Slave Select Pins as outputs:
    pinMode (slavePin, OUTPUT);
    // initialize SPI:
    SPI.begin();
  }
}

uint8_t i = 0;

void loop() {  
  SPI.beginTransaction(settingsB);
  SPI.transfer16(triangle[i]); 
  SPI.endTransaction();
  
  i = (i + 1) % triangle_len;
}