/*
* MAX31865.c
*
* Created on: Feb 19, 2024
* Author: Marwen Maghrebi
*/
#include "MAX31865.h"
extern SPI_HandleTypeDef hspi1;
bool initialized = false;
/**
* @brief Write an 8-bit value to the specified register.
* @param addr Register address.
* @param data Data to write.
*/
void writeRegister8(uint8_t addr, uint8_t data) {
addr |= 0x80; // MSB=1 for write, make sure top bit is set
uint8_t buffer[2] = {addr, data};
HAL_GPIO_WritePin(CS_GPIO_Port, CS_Pin, GPIO_PIN_RESET);
HAL_SPI_Transmit(&hspi1, buffer, 2, SPI_DELAY);
HAL_GPIO_WritePin(CS_GPIO_Port, CS_Pin, GPIO_PIN_SET);
}
/**
* @brief Read multiple bytes from the specified register.
* @param addr Register address.
* @param buffer Buffer to store the read data.
* @param n Number of bytes to read.
*/
void readRegisterN(uint8_t addr, uint8_t buffer[], uint8_t n) {
addr &= 0x7F; // MSB=0 for read, make sure top bit is not set
HAL_GPIO_WritePin(CS_GPIO_Port, CS_Pin, GPIO_PIN_RESET);
HAL_SPI_Transmit(&hspi1, &addr, 1, SPI_DELAY);
HAL_SPI_Receive(&hspi1, buffer, n, SPI_DELAY);
HAL_GPIO_WritePin(CS_GPIO_Port, CS_Pin, GPIO_PIN_SET);
}
/**
* @brief Read an 8-bit value from the specified register.
* @param addr Register address.
* @return 8-bit value read from the register.
*/
uint8_t readRegister8(uint8_t addr) {
uint8_t ret = 0;
readRegisterN(addr, &ret, 1);
return ret;
}
/**
* @brief Read a 16-bit value from the specified register.
* @param addr Register address.
* @return 16-bit value read from the register.
*/
uint16_t readRegister16(uint8_t addr) {
uint8_t buffer[2] = {0, 0};
readRegisterN(addr, buffer, 2);
uint16_t ret = (uint16_t)buffer[0]; // Cast to uint16_t before left shift
ret <<= 8;
ret |= buffer[1];
return ret;
}
/**
* @brief Read a 24-bit value from the specified register.
* @param addr Register address.
* @return 24-bit value read from the register.
*/
uint32_t readRegister24(uint8_t addr) {
uint8_t buffer[3] = {0, 0, 0};
readRegisterN(addr, buffer, 3);
uint32_t ret = (uint32_t)buffer[0];
ret <<= 8;
ret |= buffer[1];
ret <<= 8;
ret |= buffer[2];
return ret;
}
/**
* @brief Set the number of wires for the RTD configuration.
* @param wires Number of wires configuration (2, 3, or 4-wire).
*/
void setWires(max31865_numwires_t wires) {
uint8_t t = readRegister8(MAX31865_CONFIG_REG);
if (wires == MAX31865_3WIRE) {
t |= MAX31865_CONFIG_3WIRE;
} else {
t &= ~MAX31865_CONFIG_3WIRE;
}
writeRegister8(MAX31865_CONFIG_REG, t);
}
/**
* @brief Enable or disable the bias voltage on the RTD sensor.
* @param b True to enable, false to disable.
*/
void enableBias(bool b) {
uint8_t t = readRegister8(MAX31865_CONFIG_REG);
if (b) {
t |= MAX31865_CONFIG_BIAS; // Enable bias
} else {
t &= ~MAX31865_CONFIG_BIAS; // Disable bias
}
writeRegister8(MAX31865_CONFIG_REG, t);
}
/**
* @brief Enable or disable automatic conversion mode.
* @param b True to enable, false to disable.
*/
void autoConvert(bool b) {
uint8_t t = readRegister8(MAX31865_CONFIG_REG);
if (b) {
t |= MAX31865_CONFIG_MODEAUTO; // Enable auto convert
} else {
t &= ~MAX31865_CONFIG_MODEAUTO; // Disable auto convert
}
writeRegister8(MAX31865_CONFIG_REG, t);
}
/**
* @brief Enable or disable 50Hz filter.
* @param b True to enable, false to disable.
*/
void enable50Hz(bool b) {
uint8_t t = readRegister8(MAX31865_CONFIG_REG);
if (b) {
t |= MAX31865_CONFIG_FILT50HZ;
} else {
t &= ~MAX31865_CONFIG_FILT50HZ;
}
writeRegister8(MAX31865_CONFIG_REG, t);
}
/**
* @brief Set the high and low fault thresholds.
* @param lower Lower threshold.
* @param upper Upper threshold.
*/
void setThresholds(uint16_t lower, uint16_t upper) {
writeRegister8(MAX31865_LFAULTLSB_REG, lower & 0xFF);
writeRegister8(MAX31865_LFAULTMSB_REG, lower >> 8);
writeRegister8(MAX31865_HFAULTLSB_REG, upper & 0xFF);
writeRegister8(MAX31865_HFAULTMSB_REG, upper >> 8);
}
/**
* @brief Get the lower fault threshold.
* @return Lower fault threshold.
*/
uint16_t getLowerThreshold(void) {
return readRegister16(MAX31865_LFAULTMSB_REG);
}
/**
* @brief Get the upper fault threshold.
* @return Upper fault threshold.
*/
uint16_t getUpperThreshold(void) {
return readRegister16(MAX31865_HFAULTMSB_REG);
}
/**
* @brief Initialize the MAX31865 device.
* @param wires Number of wires configuration (2, 3, or 4-wire).
* @return True if initialization is successful, otherwise false.
*/
bool begin(max31865_numwires_t wires) {
if (HAL_SPI_Init(&hspi1) == HAL_OK) {
initialized = true;
} else {
initialized = false;
}
setWires(wires);
enableBias(false);
autoConvert(false);
setThresholds(0, 0xFFFF);
clearFault();
return initialized;
}
/**
* @brief Read the RTD resistance value.
* @return Raw RTD resistance value.
*/
uint16_t readRTD(void) {
clearFault();
enableBias(true);
HAL_Delay(10);
uint8_t t = readRegister8(MAX31865_CONFIG_REG);
t |= MAX31865_CONFIG_1SHOT;
writeRegister8(MAX31865_CONFIG_REG, t);
HAL_Delay(65);
uint16_t rtd = readRegister16(MAX31865_RTDMSB_REG);
enableBias(false); // Disable bias current to reduce self-heating.
rtd >>= 1; // Remove fault bit
return rtd;
}
/**
* @brief Calculate the temperature from the RTD resistance.
* @param RTDnominal Nominal resistance of the RTD at 0°C.
* @param refResistor Reference resistance value.
* @return Calculated temperature.
*/
float temperature(float RTDnominal, float refResistor) {
return calculateTemperature(readRTD(), RTDnominal, refResistor);
}
/**
* @brief Calculate the temperature from the raw RTD resistance value.
* @param RTDraw Raw RTD resistance value.
* @param RTDnominal Nominal resistance of the RTD at 0°C.
* @param refResistor Reference resistance value.
* @return Calculated temperature.
*/
float calculateTemperature(uint16_t RTDraw, float RTDnominal, float refResistor) {
float Z1, Z2, Z3, Z4, Rt, temp;
Rt = RTDraw;
Rt /= 32768;
Rt *= refResistor;
Z1 = -RTD_A;
Z2 = RTD_A * RTD_A - (4 * RTD_B);
Z3 = (4 * RTD_B) / RTDnominal;
Z4 = 2 * RTD_B;
temp = Z2 + (Z3 * Rt);
temp = (sqrt(temp) + Z1) / Z4;
if (temp >= 0) return temp;
Rt /= RTDnominal;
Rt *= 100; // Normalize to 100 ohm
float rpoly = Rt;
temp = -242.02;
temp += 2.2228 * rpoly;
rpoly *= Rt; // Square
temp += 2.5859e-3 * rpoly;
rpoly *= Rt; // ^3
temp -= 4.8260e-6 * rpoly;
rpoly *= Rt; // ^4
temp -= 2.8183e-8 * rpoly;
rpoly *= Rt; // ^5
temp += 1.5243e-10 * rpoly;
return temp;
}
/**
* @brief Read fault status from the MAX31865.
* @param fault_cycle Fault detection cycle mode.
* @return Fault status register value.
*/
uint8_t readFault(max31865_fault_cycle_t fault_cycle) {
if (fault_cycle) {
uint8_t cfg_reg = readRegister8(MAX31865_CONFIG_REG);
cfg_reg &= 0x11; // Mask out wire and filter bits
switch (fault_cycle) {
case MAX31865_FAULT_AUTO:
writeRegister8(MAX31865_CONFIG_REG, (cfg_reg | 0b10000100));
HAL_Delay(1);
break;
case MAX31865_FAULT_MANUAL_RUN:
writeRegister8(MAX31865_CONFIG_REG, (cfg_reg | 0b10001000));
return 0;
case MAX31865_FAULT_MANUAL_FINISH:
writeRegister8(MAX31865_CONFIG_REG, (cfg_reg | 0b10001100));
return 0;
case MAX31865_FAULT_NONE:
default:
break;
}
}
return readRegister8(MAX31865_FAULTSTAT_REG);
}
/**
* @brief Clear fault status on the MAX31865.
*/
void clearFault(void) {
uint8_t t = readRegister8(MAX31865_CONFIG_REG);
t &= ~0x2C;
t |= MAX31865_CONFIG_FAULTSTAT;
writeRegister8(MAX31865_CONFIG_REG, t);
}