100 lines
2.5 KiB
C
100 lines
2.5 KiB
C
#include <linux/i2c-dev.h>
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#include <i2c/smbus.h>
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#include <stdint.h>
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#include <fcntl.h>
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#include <byteswap.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <errno.h>
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#include <string.h>
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#include <sys/ioctl.h>
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#include "temperature.h"
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#define MCP9808_BUS "/dev/i2c-2"
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#define MCP9808_ADR 0x18
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#define MCP9808_MANID 0x0054
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#define MCP9808_DEVID 0x04
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#define CONFIG_REG 0x01
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#define TUPPER_REG 0x02
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#define TLOWER_REG 0x03
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#define TCRIT_REG 0x04
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#define TA_REG 0x05
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#define MANID_REG 0x06
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#define DEVID_REG 0x07
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#define RES_REG 0x08
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uint8_t get_byte_in_integer(int num, int n)
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{
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return (num >> (8*n)) & 0xff;
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}
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double get_temperature(temperature_handle_t file)
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{
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double temperature;
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int32_t reg32;
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uint8_t temperatureUpper;
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uint8_t temperatureLower;
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reg32 = i2c_smbus_read_word_data(file, TA_REG);
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reg32 = bswap_16(reg32); // swap to little endian
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reg32 = reg32 & 0x1FFF; // clear unused flags
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temperatureUpper = get_byte_in_integer(reg32, 1);
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temperatureLower = get_byte_in_integer(reg32, 0);
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if ((temperatureUpper & 0x10) == 0x10) {
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temperatureUpper = temperatureUpper & 0x0F; // clear negative flag
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temperature = 256.0 - (temperatureUpper * 16.0 + temperatureLower / 16.0);
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} else {
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temperature = (temperatureUpper * 16.0 + temperatureLower / 16.0);
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}
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return temperature;
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}
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temperature_handle_t init_temperature(void)
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{
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int file = open(MCP9808_BUS, O_RDWR);
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if (file < 0) {
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perror("Error opening temperature sensor device");
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exit(EXIT_FAILURE);
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}
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if (ioctl(file, I2C_SLAVE, MCP9808_ADR) == -1) {
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fprintf(stderr, "ERROR: setting address %d on i2c bus %s with ioctl() - %s", MCP9808_ADR, MCP9808_BUS, strerror(errno));
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exit(EXIT_FAILURE);
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}
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int32_t reg32;
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uint16_t * const reg16poi = (uint16_t *) ®32;
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uint8_t * const reg8poi = (uint8_t *) ®32;
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// Read manufactorer ID
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reg32 = i2c_smbus_read_word_data(file, MANID_REG);
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if (reg32 < 0) {
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fprintf(stderr, "Read failed on i2c bus register %d: %s\n", MANID_REG, strerror(errno));
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exit(EXIT_FAILURE);
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}
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if (bswap_16(reg16poi[0]) != MCP9808_MANID) {
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fprintf(stderr, "Invalid manufacturer ID: Expected 0x%x, got 0x%x\n", MCP9808_MANID, __bswap_16(reg16poi[0]));
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exit(EXIT_FAILURE);
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}
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// Read device ID and revision
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reg32 = i2c_smbus_read_word_data(file, DEVID_REG);
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if (reg32 < 0) {
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fprintf(stderr, "Read failed on i2c bus register %d - %s\n", DEVID_REG, strerror(errno));
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exit(EXIT_FAILURE);
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}
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if (reg8poi[0] != MCP9808_DEVID) {
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fprintf(stderr, "Invalid device ID - expected 0x%x, got 0x%x\n", MCP9808_DEVID, reg8poi[0]);
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exit(EXIT_FAILURE);
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}
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return file;
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}
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