Initial non-tested code for reading from the ESC.

src/drivers/hott_telemetry/hott_telemetry_main.c

@@ -149,6 +149,29 @@ recv_req_id(int uart, uint8_t *id)
 	return OK;
 }
 
+int
+recv_data(int uart, uint8_t *buffer, size_t *size, uint8_t id)
+{
+	usleep(100000);
+
+	static const int timeout_ms = 200;
+	struct pollfd fds[] = { { .fd = uart, .events = POLLIN } };
+
+	int i = 0;
+	if (poll(fds, 1, timeout_ms) > 0) {
+		while (true) {
+			read(uart, &buffer[i], sizeof(buffer[i]));
+
+			if (&buffer[i] == STOP_BYTE) {
+				*size = ++i;
+				id = &buffer[1];
+				return OK;
+			}
+		}
+	}
+	return ERROR;
+}
+
 int
 send_data(int uart, uint8_t *buffer, size_t size)
 {
@@ -218,6 +241,7 @@ hott_telemetry_thread_main(int argc, char *argv[])
 	bool connected = true;
 
 	while (!thread_should_exit) {
+		// Listen for and serve poll from the receiver.
 		if (recv_req_id(uart, &id) == OK) {
 			if (!connected) {
 				connected = true;
@@ -242,6 +266,26 @@ hott_telemetry_thread_main(int argc, char *argv[])
 			connected = false;
 			warnx("syncing");
 		}
+
+		// Poll the next HoTT devices.
+		// TODO(sjwilks): Currently there is only one but if there would be more we would round-robin
+		// calling one for every loop iteration.
+		build_esc_request(&buffer, &size);
+		send_data(uart, buffer, size);
+
+		// Listen for a response.
+		recv_data(uart, &buffer, &size, &id);
+
+		for (size_t i = 0; i < size; i++) {
+			warnx("%d", buffer[i]);
+		}
+
+		// Determine which moduel sent it and process accordingly.
+		if (id == ESC_SENSOR_ID) {
+			extract_esc_message(buffer);
+		} else {
+			warnx("Unknown sensor ID received: %d", id);
+		}
 	}
 
 	warnx("exiting");

src/drivers/hott_telemetry/messages.c

@@ -73,6 +73,31 @@ messages_init(void)
 	airspeed_sub = orb_subscribe(ORB_ID(airspeed));
 }
 
+void
+build_esc_request(uint8_t *buffer, size_t *size)
+{
+	struct esc_module_poll_msg msg;
+	*size = sizeof(msg);
+	memset(&msg, 0, *size);
+
+	msg.mode = BINARY_MODE_REQUEST_ID;
+	msg.id = ESC_SENSOR_ID;
+
+	memcpy(&msg, buffer, size);
+}
+
+void
+extract_esc_message(const uint8_t *buffer)
+{
+	struct esc_module_msg msg;
+	size_t size = sizeof(msg);
+	memset(&msg, 0, size);
+	memcpy(buffer, &msg, size);
+
+	// Publish it.
+
+}
+
 void 
 build_eam_response(uint8_t *buffer, size_t *size)
 {
@@ -92,7 +117,7 @@ build_eam_response(uint8_t *buffer, size_t *size)
 
 	msg.start = START_BYTE;
 	msg.eam_sensor_id = EAM_SENSOR_ID;
-	msg.sensor_id = EAM_SENSOR_TEXT_ID;
+	msg.sensor_text_id = EAM_SENSOR_TEXT_ID;
 	
 	msg.temperature1 = (uint8_t)(raw.baro_temp_celcius + 20);
 	msg.temperature2 = msg.temperature1 - BOARD_TEMP_OFFSET_DEG;
@@ -112,7 +137,6 @@ build_eam_response(uint8_t *buffer, size_t *size)
 	msg.speed_L = (uint8_t)speed & 0xff;
 	msg.speed_H = (uint8_t)(speed >> 8) & 0xff;
 
-
 	msg.stop = STOP_BYTE;
 	memcpy(buffer, &msg, *size);
 }

src/drivers/hott_telemetry/messages.h

@@ -60,6 +60,34 @@
 #define STOP_BYTE		0x7d
 #define TEMP_ZERO_CELSIUS	0x14
 
+#define ESC_SENSOR_ID			0x8e
+
+/* The ESC Module poll message. */
+struct esc_module_poll_msg {
+	uint8_t mode;
+	uint8_t id;
+};
+
+/* The Electric Air Module message. */
+struct esc_module_msg {
+	uint8_t start;			/**< Start byte */
+	uint8_t sensor_id;
+	uint8_t warning;
+	uint8_t sensor_text_id;
+	uint8_t alarm_inverse1;
+	uint8_t alarm_inverse2;
+	uint8_t temperature1;		/**< Temperature sensor 1. 20 = 0 degrees */
+	uint8_t temperature2;
+	uint8_t current_L;		/**< Current (mAh) lower 8-bits in steps of 0.1V */
+	uint8_t current_H;
+	uint8_t rpm_L;			/**< RPM Lower 8-bits In steps of 10 U/min */
+	uint8_t rpm_H;
+	uint8_t speed_L;		/**< Airspeed in km/h in steps of 1 km/h */
+	uint8_t speed_H;
+	uint8_t stop;			/**< Stop byte */
+	uint8_t checksum;		/**< Lower 8-bits of all bytes summed. */
+};
+
 /* Electric Air Module (EAM) constants. */
 #define EAM_SENSOR_ID			0x8e
 #define EAM_SENSOR_TEXT_ID		0xe0
@@ -69,7 +97,7 @@ struct eam_module_msg {
 	uint8_t start;			/**< Start byte   				*/
 	uint8_t eam_sensor_id;		/**< EAM sensor					*/
 	uint8_t warning;
-	uint8_t sensor_id;			/**< Sensor ID, why different?	*/
+	uint8_t sensor_text_id;
 	uint8_t alarm_inverse1;
 	uint8_t alarm_inverse2;
 	uint8_t cell1_L;		/**< Lipo cell voltages. Not supported.	*/
@@ -116,7 +144,7 @@ struct eam_module_msg {
 /** 
  * The maximum buffer size required to store a HoTT message.
  */
-#define MESSAGE_BUFFER_SIZE sizeof(union { 	\
+#define EAM_MESSAGE_BUFFER_SIZE sizeof(union { 	\
     struct eam_module_msg eam; 			\
 })
 
@@ -186,7 +214,11 @@ struct gps_module_msg {
     struct gps_module_msg gps; 			\
 })
 
+#define MESSAGE_BUFFER_SIZE GPS_MESSAGE_BUFFER_SIZE
+
 void messages_init(void);
+void build_esc_request(uint8_t *buffer, size_t *size);
+void extract_esc_message(const uint8_t *buffer);
 void build_eam_response(uint8_t *buffer, size_t *size);
 void build_gps_response(uint8_t *buffer, size_t *size);
 float _get_distance_to_next_waypoint(double lat_now, double lon_now, double lat_next, double lon_next);