Merge pull request #1439 from samsonact/master

sbus1_output

src/modules/px4iofirmware/sbus.c

@@ -57,6 +57,7 @@
 #define SBUS_FLAGS_BYTE		23
 #define SBUS_FAILSAFE_BIT	3
 #define SBUS_FRAMELOST_BIT	2
+#define SBUS1_FRAME_DELAY	14000
 
 /*
   Measured values with Futaba FX-30/R6108SB:
@@ -80,6 +81,7 @@ static int sbus_fd = -1;
 
 static hrt_abstime last_rx_time;
 static hrt_abstime last_frame_time;
+static hrt_abstime last_txframe_time = 0;
 
 static uint8_t	frame[SBUS_FRAME_SIZE];
 
@@ -122,10 +124,42 @@ sbus_init(const char *device)
 void
 sbus1_output(uint16_t *values, uint16_t num_values)
 {
-	char a = 'A';
-	write(sbus_fd, &a, 1);
-}
+	uint8_t byteindex = 1; /*Data starts one byte into the sbus frame. */
+	uint8_t offset = 0;
+	uint16_t value;
+	hrt_abstime now;
 
+	now = hrt_absolute_time();
+
+	if ((now - last_txframe_time) > SBUS1_FRAME_DELAY) {
+		last_txframe_time = now;
+		uint8_t	oframe[SBUS_FRAME_SIZE] = { 0x0f };
+
+		/* 16 is sbus number of servos/channels minus 2 single bit channels.
+		* currently ignoring single bit channels.  */
+
+		for (unsigned i = 0; (i < num_values) && (i < 16); ++i) {
+			value = (uint16_t)(((values[i] - SBUS_SCALE_OFFSET) / SBUS_SCALE_FACTOR) + .5f);
+
+			/*protect from out of bounds values and limit to 11 bits*/
+			if (value > 0x07ff ) {
+				value = 0x07ff;
+			}
+
+			while (offset >= 8) {
+				++byteindex;
+				offset -= 8;
+			}
+
+			oframe[byteindex] |= (value << (offset)) & 0xff;
+			oframe[byteindex + 1] |= (value >> (8 - offset)) & 0xff;
+			oframe[byteindex + 2] |= (value >> (16 - offset)) & 0xff;
+			offset += 11;
+		}
+
+		write(sbus_fd, oframe, SBUS_FRAME_SIZE);
+	}
+}
 void
 sbus2_output(uint16_t *values, uint16_t num_values)
 {