Adjust the control mapping from DSM receivers to correspond to the standard PPM control mapping for channels 0-4.

apps/px4io/comms.c

@@ -130,7 +130,7 @@ comms_main(void)
 			last_report_time = now;
 
 			/* populate the report */
-			for (int i = 0; i < system_state.rc_channels; i++)
+			for (unsigned i = 0; i < system_state.rc_channels; i++)
 				report.rc_channel[i] = system_state.rc_channel_data[i];
 			report.channel_count = system_state.rc_channels;
 			report.armed = system_state.armed;

apps/px4io/dsm.c

@@ -322,10 +322,28 @@ dsm_decode(hrt_abstime frame_time)
 		/* convert 0-1024 / 0-2048 values to 1000-2000 ppm encoding in a very sloppy fashion */
 		if (channel_shift == 11)
 			value /= 2;
+		value += 998;
 
-		/* stuff the decoded channel into the PPM input buffer */
+		/* 
-		/* XXX check actual values */
+		 * Store the decoded channel into the R/C input buffer, taking into
-		system_state.rc_channel_data[channel] = 988 + value;
+		 * account the different ideas about channel assignement that we have.
+		 *
+		 * Specifically, the first four channels in rc_channel_data are roll, pitch, thrust, yaw,
+		 * but the first four channels from the DSM receiver are thrust, roll, pitch, yaw.
+		 */
+		switch (channel) {
+		case 0:
+			channel = 2;
+			break;
+		case 1:
+			channel = 0;
+			break;
+		case 2:
+			channel = 1;
+		default:
+			break;
+		}
+		system_state.rc_channel_data[channel] = value;
 	}
 
 	/* and note that we have received data from the R/C controller */

apps/px4io/px4io.h

@@ -75,7 +75,7 @@ struct sys_state_s
 	/*
 	 * Data from the remote control input(s)
 	 */
-	int		rc_channels;
+	unsigned	rc_channels;
 	uint16_t	rc_channel_data[PX4IO_INPUT_CHANNELS];
 	uint64_t	rc_channels_timestamp;