aws iot sample: add support to remotely control an LED

The application allows to switch on and off the configured LED.

This commit adds the following configuration parameter:
  * 'user_led ': GPIO number of the LED to be remotely controlled.
    If -1, no LED is controlled, but the application simulates its status.

https://jira.digi.com/browse/DEL-4149

Signed-off-by: Tatiana Leon <tatiana.leon@digi.com>

awsiot-sample/README.md

@@ -2,7 +2,8 @@ AWS IoT device SDK Demo Application
 ===================================
 Demo application to connect devices to AWS IoT.
 
-This application monitors the CPU temperature and load.
+This application monitors the CPU temperature and load and allows to remotely
+switch on/off a device LED.
 
 The demo uploads the device Thing Shadow every minute or when the difference
 between the current value of temperature or load and the last reported is bigger
@@ -51,12 +52,35 @@ You can specify the configuration file with `-c`:
     "state" : {
       "reported" : {
         "temperature" : 45.971,
-        "cpuLoad" : 4.504505
+        "cpuLoad" : 4.504505,
+        "ledON" : false
       }
     },
     "clientToken" : "<thing_name>-3"
   }
   ```
+* To switch on the configured LED send to the topic
+  `$aws/things/<thing_name>/shadow/update`:
+  ```
+  {
+    "state" : {
+      "desired" : {
+        "ledON" : true
+      }
+    }
+  }
+  ```
+* To switch off the configured LED send to the topic
+  `$aws/things/<thing_name>/shadow/update`:
+  ```
+  {
+    "state" : {
+      "desired" : {
+        "ledON" : false
+      }
+    }
+  }
+  ```
 
 Compiling the application
 -------------------------

awsiot-sample/cfg_files/awsiotsdk.conf

@@ -65,3 +65,7 @@ temperature_variation = 1
 # By default, 10%.
 cpu_load_variation = 10
 
+# User LED: GPIO number of the LED.
+# If -1, no LED is controlled, but the application still simulates its status.
+# User LED on board are: ccimx6sbc, 34; ccimx6ulsbc, 488; ccimx6ulstarter, 75.
+user_led = -1

awsiot-sample/src/aws_config.c

@@ -47,6 +47,7 @@
 #define SETTING_CPULOAD_VARIATION	"cpu_load_variation"
 #define SETTING_CPULOAD_VARIATION_MIN	1 /* % */
 #define SETTING_CPULOAD_VARIATION_MAX	50.0 /* % */
+#define SETTING_USER_LED		"user_led"
 
 #define SETTING_UNKNOWN			"__unknown"
 
@@ -112,6 +113,8 @@ int parse_configuration(const char *const filename, aws_iot_cfg_t *aws_cfg)
 		CFG_FLOAT	(SETTING_TEMP_VARIATION,	1,		CFGF_NONE),
 		CFG_FLOAT	(SETTING_CPULOAD_VARIATION,	10,		CFGF_NONE),
 
+		CFG_INT		(SETTING_USER_LED,		-1,		CFGF_NONE),
+
 		/* Needed for unknown settings. */
 		CFG_STR		(SETTING_UNKNOWN,		NULL,		CFGF_NONE),
 		CFG_END()
@@ -199,6 +202,7 @@ static int fill_aws_iot_config(aws_iot_cfg_t *aws_cfg)
 	aws_cfg->shadow_report_rate = cfg_getint(cfg, SETTING_SHADOW_REPORT_RATE);
 	aws_cfg->temp_variation = cfg_getfloat(cfg, SETTING_TEMP_VARIATION);
 	aws_cfg->cpuload_variation = cfg_getfloat(cfg, SETTING_CPULOAD_VARIATION);
+	aws_cfg->led_gpio = cfg_getint(cfg, SETTING_USER_LED);
 
 	return 0;
 }

awsiot-sample/src/aws_config.h

@@ -49,6 +49,7 @@
  * 			(C) to report again
  * @cpuload_variation:	CPU load variation between last reported and current (%)
  * 			to report again
+ * @led_gpio:		GPIO number of the LED
  */
 typedef struct {
 	char *thing_name;
@@ -62,6 +63,7 @@ typedef struct {
 	uint32_t shadow_report_rate;
 	uint16_t temp_variation;
 	uint16_t cpuload_variation;
+	int led_gpio;
 } aws_iot_cfg_t;
 
 /*------------------------------------------------------------------------------

awsiot-sample/src/aws_control.c

@@ -35,6 +35,8 @@
 /*------------------------------------------------------------------------------
                     F U N C T I O N  D E C L A R A T I O N S
 ------------------------------------------------------------------------------*/
+static void led_actuate_callback(const char *json_string, uint32_t len,
+				  jsonStruct_t *json_struct);
 static void shadow_update_status_callback(const char *pThingName,
 					  ShadowActions_t action,
 					  Shadow_Ack_Status_t status,
@@ -175,6 +177,8 @@ IoT_Error_t disconnect_shadow_client(AWS_IoT_Client *mqtt_client)
 IoT_Error_t initialize_shadow(AWS_IoT_Client *mqtt_client,
 			      device_shadow_t *dev_shadow)
 {
+	IoT_Error_t rc = FAILURE;
+
 	device_shadow = dev_shadow;
 
 	device_shadow->temp_handler.cb = NULL;
@@ -193,9 +197,22 @@ IoT_Error_t initialize_shadow(AWS_IoT_Client *mqtt_client,
 	device_shadow->cpu_load = 0;
 	device_shadow->cpu_load_update = 0;
 
+	device_shadow->led_actuator.cb = led_actuate_callback;
+	device_shadow->led_actuator.pKey = ATTR_LED;
+	device_shadow->led_actuator.pData = &(device_shadow->led_on);
+	device_shadow->led_actuator.type = SHADOW_JSON_BOOL;
+
+	device_shadow->led_on = false;
+	device_shadow->led_update = 0;
+
 	device_shadow->aws_config = &aws_cfg;
 
-	return SUCCESS;
+	rc = aws_iot_shadow_register_delta(mqtt_client,
+					   &(device_shadow->led_actuator));
+	if (rc != SUCCESS)
+		IOT_ERROR("Unable to register Shadow Delta for LED, error: %d", rc);
+
+	return rc;
 }
 
 /**
@@ -216,9 +233,10 @@ IoT_Error_t update_shadow(AWS_IoT_Client *mqtt_client)
 		return rc;
 
 	rc = aws_iot_shadow_add_reported(json_doc_buf, size_json_doc_buf,
-					 2,
+					 3,
 					 &(device_shadow->temp_handler),
-					 &(device_shadow->cpu_load_handler));
+					 &(device_shadow->cpu_load_handler),
+					 &(device_shadow->led_actuator));
 	if (rc != SUCCESS)
 		return rc;
 
@@ -232,6 +250,35 @@ IoT_Error_t update_shadow(AWS_IoT_Client *mqtt_client)
 				     (void *) device_shadow, 4, true);
 }
 
+/**
+ * led_actuate_callback() - Callback to be executed on receiving the LED value
+ *
+ * @json_string:	Thing name of the shadow to be updated.
+ * @len:		The response of the action.
+ * @json_struct:	The struct used to parse JSON value.
+ */
+static void led_actuate_callback(const char *json_string, uint32_t len,
+				 jsonStruct_t *json_struct)
+{
+	bool status = false;
+	int led_gpio = aws_cfg.led_gpio;
+	IOT_UNUSED(json_string);
+	IOT_UNUSED(len);
+
+	if (json_struct == NULL)
+		return;
+
+	status = *(bool *) (json_struct->pData);
+
+	if (led_gpio <= -1 ||
+	    (led_gpio > -1 && set_gpio_value(led_gpio, status) == 0)) {
+		IOT_INFO("Delta - LED state changed to %s", status ? ON : OFF);
+		device_shadow->led_update = 1;
+	} else {
+		IOT_ERROR("Error setting LED to %s", status ? ON : OFF);
+	}
+}
+
 /**
  * shadow_update_status_callback() - AWS IoT Device SDK update status callback
  *
@@ -270,6 +317,7 @@ static void shadow_update_status_callback(const char *pThingName,
 		IOT_INFO("Shadow update accepted");
 		dev_shadow->temp_update = 0;
 		dev_shadow->cpu_load_update = 0;
+		dev_shadow->led_update = 0;
 		break;
 	}
 }

awsiot-sample/src/aws_control.h

@@ -30,6 +30,10 @@
 ------------------------------------------------------------------------------*/
 #define ATTR_TEMPERATURE			"temperature"
 #define ATTR_CPU_LOAD				"cpuLoad"
+#define ATTR_LED				"ledON"
+
+#define ON					"ON"
+#define OFF					"OFF"
 
 /*------------------------------------------------------------------------------
                  D A T A    T Y P E S    D E F I N I T I O N S
@@ -44,6 +48,9 @@
  * @cpu_load:		Last CPU load reported (%)
  * @cpu_load_handler:	CPU load handler
  * @cpu_load_update:	CPU load value locally updated
+ * @led_on:		Last LED value reported
+ * @led_actuator:	LED actuator
+ * @led_update:		LED value locally updated
  * @update_required:	Update shadow immediately
  * @aws_config:		AWS IoT Decive SDK configuration struct
  */
@@ -54,6 +61,9 @@ typedef struct {
 	double cpu_load;
 	jsonStruct_t cpu_load_handler;
 	unsigned int cpu_load_update;
+	bool led_on;
+	jsonStruct_t led_actuator;
+	unsigned int led_update;
 	unsigned int update_required;
 	aws_iot_cfg_t *aws_config;
 } device_shadow_t;

awsiot-sample/src/device_control.c

@@ -18,6 +18,8 @@
  */
 
 #include <aws_iot_log.h>
+#include <dirent.h>
+#include <stdarg.h>
 #include <string.h>
 #include <unistd.h>
 
@@ -31,10 +33,18 @@
 #define FILE_CPU_TEMP		"/sys/class/thermal/thermal_zone0/temp"
 #define FILE_CPU_LOAD		"/proc/stat"
 
+#define PATH_GPIO_FILES		"/sys/class/gpio/"
+#define EXPORT_FILE		PATH_GPIO_FILES "export"
+#define GPIO_DIR_FILE_FORMAT	PATH_GPIO_FILES "gpio%d/direction"
+#define GPIO_VALUE_FILE_FORMAT	PATH_GPIO_FILES "gpio%d/value"
+
 /*------------------------------------------------------------------------------
                     F U N C T I O N  D E C L A R A T I O N S
 ------------------------------------------------------------------------------*/
+static int export_gpio(int gpio);
+static int is_gpio_exported( int gpio);
 static long read_file(const char * path, char *buffer, long bytes_to_read);
+static int write_file(const char *const path, const char *const format, ...);
 
 /*------------------------------------------------------------------------------
                      F U N C T I O N  D E F I N I T I O N S
@@ -114,6 +124,158 @@ double get_cpu_temp(void)
 	return temperature / 1000;
 }
 
+/**
+ * init_gpio() - Export and initialize a GPIO
+ *
+ * @gpio:		GPIO kernel number
+ *
+ * The provided GPIO is exported and configured as input with edge "none".
+ *
+ * Return: 0 if the GPIO was initialized successfully, -1 otherwise.
+ */
+int init_gpio(int gpio)
+{
+	int error = 0;
+
+	if (gpio < 0) {
+		IOT_ERROR("Bad GPIO number '%d'", gpio);
+		return -1;
+	}
+
+	/* Export the GPIO. */
+	if (export_gpio(gpio) != 0) {
+		IOT_ERROR("Cannot initialize GPIO %d", gpio);
+		return -1;
+	}
+
+	/* Configure GPIO as input. */
+	error = set_gpio_direction(gpio, INPUT);
+	if (error != 0)
+		IOT_ERROR("Cannot initialize GPIO %d", gpio);
+
+	return error;
+}
+
+/**
+ * set_gpio_value() - Set GPIO value, if it is configured as an output
+ *
+ * @gpio:	GPIO kernel number.
+ * @value:	1 to set to high, 0 to low.
+ *
+ * Return: 0 if the GPIO was successfully set, -1 otherwise.
+ */
+int set_gpio_value(int gpio, unsigned int value)
+{
+	char gpio_path[MAX_LENGTH] = {0};
+
+	if (gpio < 0) {
+		IOT_ERROR("Bad GPIO number '%d'", gpio);
+		return -1;
+	}
+
+	snprintf(gpio_path, MAX_LENGTH, GPIO_VALUE_FILE_FORMAT, gpio);
+
+	if (write_file(gpio_path, "%d", value) != 0) {
+		IOT_ERROR("Error setting GPIO %d value to %s (%d)", gpio,
+			  value ? "high" : "low", value);
+		return -1;
+	}
+
+	return 0;
+}
+
+/**
+ * set_gpio_direction() - Set GPIO direction, input or output
+ *
+ * @gpio:		GPIO kernel number.
+ * @out:		1 to configure as out, 0 as input.
+ *
+ * Return: 0 if the GPIO was successfully configured, -1 otherwise.
+ */
+int set_gpio_direction(int gpio, unsigned int out)
+{
+	char gpio_path[MAX_LENGTH] = {0};
+	char buf[MAX_LENGTH] = {0};
+
+	IOT_DEBUG("GPIO %d as %s", gpio, out ? "Output" : "Input");
+
+	if (gpio < 0) {
+		IOT_ERROR("Bad GPIO number '%d'", gpio);
+		return -1;
+	}
+
+	snprintf(gpio_path, MAX_LENGTH, GPIO_DIR_FILE_FORMAT, gpio);
+
+	if (out)
+		strcpy(buf, "out");
+	else
+		strcpy(buf, "in");
+
+	if (write_file(gpio_path, "%s", buf) != 0) {
+		IOT_ERROR("Error setting GPIO %d direction to '%s'", gpio,
+			  out ? "Output" : "Input");
+		return -1;
+	}
+
+	return 0;
+}
+
+/**
+ * export_gpio() - Export a GPIO
+ *
+ * @gpio:	GPIO kernel number.
+ *
+ * Return: 0 if the GPIO was successfully exported, -1 otherwise.
+ */
+static int export_gpio(int gpio)
+{
+	if (gpio < 0) {
+		IOT_ERROR("Bad GPIO number '%d'", gpio);
+		return -1;
+	}
+
+	if (is_gpio_exported(gpio))
+		return 0;
+
+	if (write_file(EXPORT_FILE, "%d", gpio) != 0) {
+		IOT_ERROR("GPIO %d not exported, error writing to 'export' file",
+			  gpio);
+		return -1;
+	}
+
+	/* Check if the GPIO was really exported. */
+	if (!is_gpio_exported(gpio)) {
+		IOT_ERROR("GPIO %d not exported", gpio);
+		return -1;
+	}
+
+	return 0;
+}
+
+/**
+ * is_gpio_exported() - Check if a GPIO is exported
+ *
+ * @gpio:	GPIO kernel number.
+ *
+ * Return: 1 if the GPIO is exported, 0 otherwise.
+ */
+static int is_gpio_exported( int gpio)
+{
+	char dir_path[MAX_LENGTH] = {0};
+	DIR *dir = NULL;
+
+	snprintf(dir_path, MAX_LENGTH, PATH_GPIO_FILES "gpio%d", gpio);
+
+	dir = opendir(dir_path);
+
+	if (dir) {
+		closedir(dir);
+		return 1;
+	} else {
+		return 0;
+	}
+}
+
 /**
  * read_file() - Read the given file and returns its contents
  *
@@ -150,3 +312,46 @@ static long read_file(const char * path, char *buffer, long bytes_to_read)
 
 	return read_size;
 }
+
+/**
+ * write_file() - Write data to a file
+ *
+ * @path:	Absolute path of the file to be written.
+ * @format:	String that contains the text to be written to the file.
+ *
+ * Return: 0 if the file was written successfully, -1 otherwise.
+ */
+static int write_file(const char *const path, const char *const format, ...)
+{
+	va_list args;
+	FILE *f = NULL;
+	int len, error = 0;
+
+	if (access(path, W_OK) != 0) {
+		IOT_DEBUG("File cannot be written: %s", path);
+		return -1;
+	}
+
+	va_start(args, format);
+
+	f = fopen(path, "w");
+	if (f == NULL) {
+		IOT_DEBUG("fopen error: %s", path);
+		error = -1;
+		goto done;
+	}
+
+	len = vfprintf(f, format, args);
+	if (len < 0) {
+		IOT_DEBUG("vfprintf error: %s", path);
+		error = -1;
+	}
+
+	fsync(fileno(f));
+	fclose(f);
+
+done:
+	va_end(args);
+
+	return error;
+}

awsiot-sample/src/device_control.h

@@ -20,10 +20,19 @@
 #ifndef DEVICE_CONTROL_H_
 #define DEVICE_CONTROL_H_
 
+/*------------------------------------------------------------------------------
+                             D E F I N I T I O N S
+------------------------------------------------------------------------------*/
+#define INPUT		0
+#define OUTPUT		1
+
 /*------------------------------------------------------------------------------
                     F U N C T I O N  D E C L A R A T I O N S
 ------------------------------------------------------------------------------*/
 double get_cpu_load(void);
 double get_cpu_temp(void);
+int init_gpio(int gpio);
+int set_gpio_value(int gpio, unsigned int value);
+int set_gpio_direction(int gpio, unsigned int out);
 
 #endif /* DEVICE_CONTROL_H_ */

awsiot-sample/src/main.c

@@ -58,6 +58,7 @@
                     F U N C T I O N  D E C L A R A T I O N S
 ------------------------------------------------------------------------------*/
 static int start_aws_iot(const char *config_file);
+static int initialize_system(device_shadow_t *dev_shadow);
 static int check_stop(void);
 static void add_sigkill_signal(void);
 static void graceful_shutdown(void);
@@ -160,6 +161,9 @@ static int start_aws_iot(const char *config_file)
 		goto done;
 	}
 
+	if (initialize_system(&device_shadow) != 0)
+		IOT_WARN("Unable to initialize the whole system");
+
 	time_start = time(NULL);
 	/* Loop and publish shadow changes */
 	while (rc == NETWORK_ATTEMPTING_RECONNECT ||
@@ -189,7 +193,8 @@ static int start_aws_iot(const char *config_file)
 						 load >= (device_shadow.cpu_load + aws_cfg->cpuload_variation));
 
 		change_shadow = device_shadow.temp_update ||
-				device_shadow.cpu_load_update;
+				device_shadow.cpu_load_update ||
+				device_shadow.led_update;
 
 		if (change_shadow ||
 		    (time(NULL) - time_start) >= aws_cfg->shadow_report_rate) {
@@ -206,8 +211,15 @@ static int start_aws_iot(const char *config_file)
 				IOT_INFO(
 					 "CPU Load variation greater than %d%%\n",
 					 aws_cfg->cpuload_variation);
+			if (device_shadow.led_update)
+				IOT_INFO(
+					 "LED changed to %s\n",
+					 device_shadow.led_on ? ON : OFF);
 			IOT_INFO("Temperature: %fC", t);
 			IOT_INFO("CPU Load: %f%%", load);
+			IOT_INFO(
+				 "LED status: %s",
+				 device_shadow.led_on ? ON : OFF);
 			IOT_INFO("=========================================\n");
 
 			rc = update_shadow(&mqtt_client);
@@ -228,6 +240,29 @@ done:
 	return rc;
 }
 
+/*
+ * initialize_system() - Stop application
+ *
+ * @dev_shadow:		Device shadow.
+ *
+ * Return: 0 if it is successfully initialized, -1 otherwise.
+ */
+static int initialize_system(device_shadow_t *dev_shadow)
+{
+	int led_gpio = dev_shadow->aws_config->led_gpio;
+
+	if (led_gpio > -1 &&
+	    (init_gpio(led_gpio) != 0 ||
+	     set_gpio_direction(led_gpio, OUTPUT) != 0 ||
+	     set_gpio_value(led_gpio, dev_shadow->led_on) != 0)) {
+		IOT_ERROR("Unable to initialize User LED");
+		dev_shadow->aws_config->led_gpio = -1;
+		return -1;
+	}
+
+	return 0;
+}
+
 /*
  * check_stop() - Stop application
  *