Implement IoT temperature measuring

iot/Makefile

@@ -1,3 +1,3 @@
-all: main.c
-	$(CC) -lmosquitto main.c
+all: main.c mqtt.c temperature.c
+	$(CC) -lmosquitto -lpthread -li2c main.c mqtt.c temperature.c
 

iot/main.c

@@ -1,43 +1,46 @@
-#include <mosquitto.h>
+#include <pthread.h>
 #include <stdlib.h>
+#include <unistd.h>
+#include <stdbool.h>
+#include <string.h>
 #include <stdio.h>
 
-#include "config.h"
+#include "mqtt.h"
+#include "temperature.h"
 
-void on_connect(struct mosquitto *client, void *obj, int rc)
+void *watch_temperature(void *arg)
 {
-	if (rc != 0) {
-		fprintf(stderr, "%s\n", mosquitto_connack_string(rc));
-		return;
+	init_temperature();
+
+	get_temperature();
+
+	while (true) {
+		double temperature = get_temperature();
+
+		char *str = malloc(snprintf(NULL, 0, "%lf", temperature) + 1);
+		sprintf(str, "%lf", temperature);
+
+		mqtt_send_message("/temperature", str);
+
+		free(str);
+
+		printf("Temperature: %lf\n", temperature);
+
+		sleep(60);
 	}
 
-	puts("Connected to " MQTT_IP);
+	return NULL;
 }
 
-void on_message(struct mosquitto *mosq, void *obj, const struct mosquitto_message *message)
+void mqtt_on_connect(void)
 {
-	printf("Received message on topic %s\n", message->topic);
+	pthread_t temperature_thread;
+	pthread_create(&temperature_thread, NULL, watch_temperature, NULL);
 }
 
 int main(void)
 {
-	int version[3];
-	mosquitto_lib_init();
-	mosquitto_lib_version(&version[0], &version[1], &version[2]);
-	printf("Using mosquitto library version %i.%i.%i\n", version[0], version[1], version[2]);
-
-	struct mosquitto *mosq = mosquitto_new(NULL, true, NULL);
-
-	mosquitto_connect_callback_set(mosq, on_connect);
-	mosquitto_message_callback_set(mosq, on_message);
-
-	mosquitto_username_pw_set(mosq, MQTT_USER, MQTT_PASSWORD);
-	mosquitto_connect(mosq, MQTT_IP, MQTT_PORT, 60);
-
-	mosquitto_loop_forever(mosq, -1, 1);
-
-	mosquitto_destroy(mosq);
-	mosquitto_lib_cleanup();
+	init_mqtt();
 
 	return EXIT_SUCCESS;
 }

iot/mqtt.c

@@ -0,0 +1,57 @@
+#include <mosquitto.h>
+#include <stdio.h>
+#include <string.h>
+#include <stdbool.h>
+
+#include "config.h"
+
+struct mosquitto *mosq;
+
+void mqtt_on_connect(void);
+
+void on_connect(struct mosquitto *client, void *obj, int rc)
+{
+	if (rc != 0) {
+		fprintf(stderr, "%s\n", mosquitto_connack_string(rc));
+		return;
+	}
+
+	puts("Connected to " MQTT_IP);
+
+	mqtt_on_connect();
+}
+
+void on_message(struct mosquitto *mosq, void *obj, const struct mosquitto_message *message)
+{
+	printf("Received message on topic %s\n", message->topic);
+}
+
+void mqtt_send_message(char *topic, char *message)
+{
+	int result = mosquitto_publish(mosq, NULL, topic, strlen(message), message, 0, false);
+	if (result != MOSQ_ERR_SUCCESS) {
+		fprintf(stderr, "Error sending message: %d\n", result);
+	}
+}
+
+void init_mqtt(void)
+{
+	int version[3];
+	mosquitto_lib_init();
+	mosquitto_lib_version(&version[0], &version[1], &version[2]);
+	printf("Using mosquitto library version %i.%i.%i\n", version[0], version[1], version[2]);
+
+	mosq = mosquitto_new(NULL, true, NULL);
+
+	mosquitto_connect_callback_set(mosq, on_connect);
+	mosquitto_message_callback_set(mosq, on_message);
+
+	mosquitto_username_pw_set(mosq, MQTT_USER, MQTT_PASSWORD);
+	mosquitto_connect(mosq, MQTT_IP, MQTT_PORT, 60);
+
+	mosquitto_loop_forever(mosq, -1, 1);
+
+	mosquitto_destroy(mosq);
+	mosquitto_lib_cleanup();
+}
+

iot/mqtt.h

@@ -0,0 +1,4 @@
+void init_mqtt(void);
+
+void mqtt_send_message(char *topic, char *message);
+

iot/temperature.c

@@ -0,0 +1,94 @@
+#include <linux/i2c-dev.h>
+#include <i2c/smbus.h>
+#include <stdint.h>
+#include <fcntl.h>
+#include <byteswap.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <string.h>
+#include <sys/ioctl.h>
+
+#define MPC9808_BUS	"/dev/i2c-2"
+#define MPC9808_ADR	0x18
+
+#define CONFIG_REG 0x01
+#define TUPPER_REG 0x02
+#define TLOWER_REG 0x03
+#define TCRIT_REG  0x04
+#define TA_REG     0x05
+#define MANID_REG  0x06
+#define DEVID_REG  0x07
+#define RES_REG    0x08
+
+int file;
+
+uint8_t get_byte_in_integer(int num, int n)
+{
+	return (num >> (8*n)) & 0xff;
+}
+
+double get_temperature()
+{
+	double temperature;
+	int32_t reg32;
+	uint8_t temperatureUpper;
+	uint8_t temperatureLower;
+
+	reg32 = i2c_smbus_read_word_data(file, TA_REG);
+	reg32 = bswap_16(reg32); // swap to little endian
+	reg32 = reg32 & 0x1FFF; // clear unused flags
+	temperatureUpper = get_byte_in_integer(reg32, 1);
+	temperatureLower = get_byte_in_integer(reg32, 0);
+
+	if ((temperatureUpper & 0x10) == 0x10) {
+			temperatureUpper = temperatureUpper & 0x0F; // clear negative flag
+			temperature = 256.0 - (temperatureUpper * 16.0 + temperatureLower / 16.0);
+	} else {
+			temperature = (temperatureUpper * 16.0 + temperatureLower / 16.0);
+	}
+
+	return temperature;
+}
+
+void init_temperature(void)
+{
+	file = open(MPC9808_BUS, O_RDWR);
+	if (file < 0) {
+		fprintf(stderr, "Error opening temperature sensor device (%s): %s\n", MPC9808_BUS, strerror(errno));
+		exit(1);
+	}
+
+	if (ioctl(file, I2C_SLAVE, MPC9808_ADR) == -1) {
+		fprintf(stderr, "ERROR: setting  address %d on i2c bus %s with ioctl() - %s", MPC9808_ADR, MPC9808_BUS, strerror(errno));
+		exit(1);
+	}
+
+	int32_t reg32;
+	uint16_t * const reg16poi = (uint16_t *) &reg32;
+	uint8_t  * const reg8poi  = (uint8_t *)  &reg32;
+
+	// Read manufactorer ID
+	reg32 = i2c_smbus_read_word_data(file, MANID_REG);
+
+	if ( reg32 < 0 ) {
+			fprintf(stderr, "ERROR: Read failed  on i2c bus register %d - %s\n",  MANID_REG,strerror(errno));
+			exit(1);
+	}
+	if (bswap_16(reg16poi[0]) != 0x0054) {
+			fprintf(stderr, "Manufactorer ID wrong is 0x%x should be 0x54\n",__bswap_16(reg16poi[0]));
+			exit(1);
+	}
+
+	// Read device ID and revision
+	reg32 = i2c_smbus_read_word_data(file, DEVID_REG);
+	if (reg32 < 0) {
+			fprintf(stderr, "ERROR: Read failed  on i2c bus register %d - %s\n",  DEVID_REG,strerror(errno) );
+			exit(1);
+	}
+	if (reg8poi[0] != 0x04) {
+			fprintf(stderr, "Manufactorer ID OK but device ID wrong is 0x%x should be 0x4\n",reg8poi[0]);
+			exit(1);
+	}
+}
+

iot/temperature.h

@@ -0,0 +1,4 @@
+void init_temperature();
+
+double get_temperature();
+