mt6835_res.ino

/*
 *
 *   Dummy Header
 *
 *   (if this is not here, i cant read the code)
 *
 */

#include <Arduino.h>
#include <SPI.h>

#define MT6835_REG_ABZ_RES1 0x007
#define MT6835_REG_ABZ_RES2 0x008

#define MT6835_OP_READ  0b0011
#define MT6835_OP_WRITE 0b0110

#define MT6835_WRITE_ACK 0x55

int startSPI = 2; //pin to set the slave active

union MT6835ABZRes {
	struct {
		uint8_t ab_swap:1;
		uint8_t abz_off:1;
		uint8_t abz_res_low:6;
	};
	uint8_t reg;
};

union MT6835Command {
	struct {
		uint32_t unused:8;
		uint32_t data:8;
		uint32_t addr:12;
		uint32_t cmd:4;
	};
	uint32_t val;
};

void setup() {
  pinMode(startSPI, OUTPUT);
  pinMode(LED_BUILTIN, OUTPUT);
  digitalWrite(LED_BUILTIN, LOW);
 //SPI.begin();
 //SPI.beginTransaction(SPISettings(1000000, MSBFIRST, SPI_MODE3));
 //SPI.setBitOrder(MSBFIRST);

  Serial.begin(115200);
}

void loop() {

  setABZResolution(10240);

  writeEEPROM();
  delay(7000); //wait at least 6s
  digitalWrite(LED_BUILTIN, HIGH);
  while (1) {
    delay(1000);
  }
}


void setABZResolution(uint16_t res){
    uint8_t hi = (res >> 6);
    MT6835ABZRes lo = {
			.reg = readRegister(MT6835_REG_ABZ_RES2)
	};
    lo.abz_res_low = (res & 0x3F);
    writeRegister(MT6835_REG_ABZ_RES1, hi);
    writeRegister(MT6835_REG_ABZ_RES2, lo.reg);
};

bool writeRegister(uint16_t reg, uint8_t value) {
    MT6835Command cmd;
    cmd.cmd = MT6835_OP_WRITE;
    cmd.addr = reg;
    cmd.data = value;
    transfer24(&cmd);
    return cmd.data == MT6835_WRITE_ACK;
};

uint8_t readRegister(uint16_t reg) {
    MT6835Command cmd;
    cmd.cmd = MT6835_OP_READ;
    cmd.addr = reg;
    transfer24(&cmd);
    return cmd.data;
};

void transfer24(MT6835Command* outValue) {
    uint32_t buff = __builtin_bswap32(outValue->val);
    SPI.beginTransaction(SPISettings(1000000, MSBFIRST, SPI_MODE3));

    digitalWrite(startSPI, LOW);
    SPI.transfer(&buff, 3);

    digitalWrite(startSPI, HIGH);
    SPI.endTransaction();
    outValue->val = __builtin_bswap32(buff);
};

bool writeEEPROM(){
    delay(1); // wait at least 1ms
    MT6835Command cmd;
    cmd.cmd = MT6835_OP_PROG;
    cmd.addr = 0x000;
    transfer24(&cmd);
    return cmd.data == MT6835_WRITE_ACK;
};