Added files (not yet modified)

sgp40.c

@@ -0,0 +1,186 @@
+/*
+ * SGP40.c
+ *
+ *  Created on: Jan 9, 2022
+ *      Author: david
+ */
+
+#include <sgp40.h>
+#include "main.h" /* for uart_disable_interrupts() */
+
+int8_t sgp40_send_cmd(sgp40_cmd_t cmd)
+{
+	uint8_t buffer[32];
+	int result;
+
+	// start measurement
+	buffer[0] = cmd >> 8;
+	buffer[1] = cmd & 0x00ff;
+	uart_disable_interrupts();
+	result = i2c_transmit(SGP40_I2C_ADDRESS<<1, buffer, 2);
+	uart_enable_interrupts();
+	if (result == I2C_ERROR_TX_INCOMPLETE) {
+		return SGP40_ERROR;
+	}
+
+	/* Sensirion sensors return NACK after last byte (so NACK at the end is ok) */
+	return SGP40_OK;
+}
+
+int8_t sgp40_measure_raw_signal(uint16_t * voc_ticks)
+{
+	uint8_t buffer[32];
+	int result;
+
+	/* Start measurement */
+	buffer[0] = 0x26;
+	buffer[1] = 0x0F;
+	buffer[2] = 0x80;
+	buffer[3] = 0x00;
+	buffer[4] = 0xA2;
+	buffer[5] = 0x66;
+	buffer[6] = 0x66;
+	buffer[7] = 0x93;
+
+	/* Returns NACK if CRC is wrong */
+	uart_disable_interrupts();
+	result = i2c_transmit(SGP40_I2C_ADDRESS<<1, buffer, 8);
+	uart_enable_interrupts();
+	if (result != I2C_OK) {
+		return SGP40_ERROR;
+	}
+
+	LL_mDelay(SGP40_MAX_MEAS_DURATION_MS); // 30ms
+
+	uart_disable_interrupts();
+	result = i2c_receive(SGP40_I2C_ADDRESS<<1, buffer, 3);
+	uart_enable_interrupts();
+	if (result != I2C_OK)
+	{
+		return SGP40_ERROR;
+	}
+
+	*voc_ticks = (buffer[0] << 8) + buffer[1];
+	uint8_t voc_ticks_crc = buffer[2];
+	uint8_t crc_correct = crc8_calculate(buffer, 2) == voc_ticks_crc;
+	if (!crc_correct) {
+		return SGP40_CRC8_ERROR;
+	}
+	return SGP40_OK;
+
+}
+
+int8_t sgp40_measure_raw_signal_compensated(uint16_t * voc_ticks, uint16_t relative_humidity, int16_t temperature)
+{
+	uint8_t buffer[32];
+	int result;
+
+	uint16_t rh_ticks = (uint16_t)((uint32_t)relative_humidity * 65535 / 100);
+	uint16_t t_ticks = (uint16_t)(((uint32_t)temperature/10 + 45) * 65535 / 175);
+
+	buffer[0] = SGP40_MEASURE_RAW_SIGNAL >> 8;
+	buffer[1] = SGP40_MEASURE_RAW_SIGNAL & 0x00ff;
+	buffer[2] = (uint8_t)(rh_ticks >> 8);
+	buffer[3] = (uint8_t)rh_ticks;
+	buffer[4] = crc8_calculate(buffer+2, 2);
+	buffer[5] = (uint8_t)(t_ticks >> 8);
+	buffer[6] = (uint8_t)t_ticks;
+	buffer[7] = crc8_calculate(buffer+5, 2);
+
+	/* Returns NACK if CRC is wrong */
+	uart_disable_interrupts();
+	result = i2c_transmit(SGP40_I2C_ADDRESS<<1, buffer, 8);
+	uart_enable_interrupts();
+	if (result != I2C_OK) {
+		return SGP40_ERROR;
+	}
+
+	LL_mDelay(SGP40_MAX_MEAS_DURATION_MS); // 30ms
+
+	uart_disable_interrupts();
+	result = i2c_receive(SGP40_I2C_ADDRESS<<1, buffer, 3);
+	uart_enable_interrupts();
+	if (result != I2C_OK)
+	{
+		return SGP40_ERROR;
+	}
+
+	*voc_ticks = (buffer[0] << 8) + buffer[1];
+	uint8_t voc_ticks_crc = buffer[2];
+	uint8_t crc_correct = crc8_calculate(buffer, 2) == voc_ticks_crc;
+	if (!crc_correct) {
+		return SGP40_CRC8_ERROR;
+	}
+	return SGP40_OK;
+}
+
+int8_t SGP40_execute_self_test ( uint8_t * test_result)
+{
+	uint8_t buffer[16];
+	int8_t result;
+
+	result = sgp40_send_cmd(SGP40_EXECUTE_SELF_TEST);
+	if (result != I2C_OK) {
+		return SGP40_ERROR;
+	}
+
+	LL_mDelay(350);
+
+	uart_disable_interrupts();
+	result = i2c_receive(SGP40_I2C_ADDRESS << 1, buffer, 3);
+	uart_enable_interrupts();
+	if (result != I2C_OK) {
+		return SGP40_ERROR;
+	}
+
+	test_result = buffer[0];
+	uint8_t test_result_crc = buffer[2];
+
+	uint8_t crc_correct = crc8_calculate(buffer, 2) == test_result_crc;
+	if (!crc_correct) {
+		return SGP40_CRC8_ERROR;
+	}
+	return SGP40_OK;
+}
+
+int8_t SGP40_get_serial_number(uint8_t serial[6])
+{
+	uint8_t buffer[16];
+
+	uart_disable_interrupts();
+	sgp40_send_cmd(SGP40_GET_SERIAL_NUMBER);
+	uart_enable_interrupts();
+
+	LL_mDelay(5);
+
+	uart_disable_interrupts();
+	i2c_receive(SGP40_I2C_ADDRESS << 1, buffer, 9);
+	uart_enable_interrupts();
+
+	serial[0] = buffer[0];
+	serial[1] = buffer[1];
+	uint8_t crc_ser01 = buffer[3];
+	serial[2] = buffer[4];
+	serial[3] = buffer[5];
+	uint8_t crc_ser23 = buffer[6];
+	serial[4] = buffer[7];
+	serial[5] = buffer[8];
+	uint8_t crc_ser45 = buffer[9];
+
+	uint8_t crc_correct = crc8_calculate(buffer, 2) == crc_ser01;
+	crc_correct &= crc8_calculate(buffer + 3, 2) == crc_ser23;
+	crc_correct &= crc8_calculate(buffer + 6, 2) == crc_ser45;
+	if (!crc_correct) {
+		return SGP40_CRC8_ERROR;
+	}
+	return SGP40_OK;
+}
+
+int8_t SGP40_turn_heater_off(void)
+{
+	return sgp40_send_cmd(SGP40_TURN_HEATER_OFF);
+}
+int8_t SGP40_soft_reset(void)
+{
+	return sgp40_send_cmd(SGP40_SOFT_RESET);
+}

sgp40.h

@@ -0,0 +1,50 @@
+/*
+ * sgp4x.h
+ *
+ *  Created on: Jan 9, 2022
+ *      Author: david
+ */
+
+#ifndef INC_SGP40_H_
+#define INC_SGP40_H_
+
+
+#include "stdint.h"
+#include "stm32l0xx_ll_i2c.h"
+#include "stm32l0xx_ll_utils.h"
+#include "i2c.h"
+#include "crc8.h"
+
+/*
+ * Defines & macros
+ */
+
+#define SGP40_I2C_ADDRESS 0x59
+#define SGP40_MAX_MEAS_DURATION_MS 50
+
+/*
+ * Return values
+ */
+
+#define SGP40_OK 0
+#define SGP40_ERROR -1 // generic error
+#define SGP40_CRC8_ERROR -2 // checksum failed
+
+typedef enum {
+	SGP40_MEASURE_RAW_SIGNAL	= 0x260F,
+	SGP40_EXECUTE_SELF_TEST		= 0x280E,
+	SGP40_TURN_HEATER_OFF		= 0x3615,
+	SGP40_GET_SERIAL_NUMBER		= 0x3682,
+	SGP40_SOFT_RESET			= 0x0006
+} sgp40_cmd_t;
+
+int8_t sgp40_send_cmd(sgp40_cmd_t cmd);
+
+int8_t sgp40_measure_raw_signal (uint16_t * voc_ticks);
+int8_t sgp40_measure_raw_signal_compensated (uint16_t * voc_ticks, uint16_t relative_humidity, int16_t temperature);
+int8_t sgp40_execute_self_test ( uint8_t * test_result);
+int8_t sgp40_get_serial_number ( uint8_t serial[6]);
+int8_t sgp40_turn_heater_off ( void );
+int8_t sgp40_soft_reset ( void );
+
+#endif /* INC_SGP40_H_ */