rc: dsm allow full range

src/lib/rc/dsm.cpp

@@ -81,6 +81,7 @@ static unsigned dsm_partial_frame_count;	/**< Count of bytes received for curren
 static unsigned dsm_channel_shift = 0;			/**< Channel resolution, 0=unknown, 10=10 bit (1024), 11=11 bit (2048) */
 static unsigned dsm_frame_drops = 0;			/**< Count of incomplete DSM frames */
 static uint16_t dsm_chan_count = 0;         /**< DSM channel count */
+static uint16_t dsm_chan_count_prev = 0;    /**< last valid DSM channel count */
 
 /**
  * Attempt to decode a single channel raw channel datum
@@ -135,7 +136,7 @@ static bool dsm_decode_channel(uint16_t raw, unsigned shift, uint8_t &channel, u
 
 		// Spektrum range is 903μs to 2097μs (Specification for Spektrum Remote Receiver Interfacing Rev G 9.1)
 		//  ±100% travel is 1102µs to 1898 µs
-		if (value < 990 || value > 2010) {
+		if (value < 903 || value > 2097) {
 			// if the value is unrealistic, fail the parsing entirely
 			PX4_DEBUG("channel %d invalid range %d", channel, value);
 			return false;
@@ -190,12 +191,14 @@ static bool dsm_decode_channel(uint16_t raw, unsigned shift, uint8_t &channel, u
 
 		// Spektrum range is 903μs to 2097μs (Specification for Spektrum Remote Receiver Interfacing Rev G 9.1)
 		//  ±100% travel is 1102µs to 1898 µs
-		if (value < 990 || value > 2010) {
+		if (value < 903 || value > 2097) {
 			// if the value is unrealistic, fail the parsing entirely
 			PX4_DEBUG("channel %d invalid range %d", channel, value);
 			return false;
 		}
 
+		PX4_DEBUG(stderr, "CH%d=%d(0x%02x), ", channel, value, raw);
+
 		return true;
 	}
 
@@ -215,6 +218,7 @@ static bool dsm_guess_format(bool reset)
 
 	/* reset the 10/11 bit sniffed channel masks */
 	if (reset) {
+		PX4_DEBUG("dsm_guess_format reset");
 		cs10 = 0;
 		cs11 = 0;
 		samples = 0;
@@ -283,8 +287,8 @@ static bool dsm_guess_format(bool reset)
 	printf("dsm guess format: samples: %d %s\n", samples, (reset) ? "RESET" : "");
 #endif
 
-	/* wait until we have seen plenty of frames - 5 should normally be enough */
+	/* wait until we have seen plenty of frames */
-	if (samples < 5) {
+	if (samples < 10) {
 		return false;
 	}
 
@@ -597,6 +601,7 @@ bool dsm_decode(hrt_abstime frame_time, uint16_t *values, uint16_t *num_values,
 		// abort if channel already found, no duplicate channels per DSM frame
 		if (channels_found[channel]) {
 			PX4_DEBUG("duplicate channel %d\n\n", channel);
+			dsm_guess_format(true);
 			return false;
 
 		} else {
@@ -605,6 +610,7 @@ bool dsm_decode(hrt_abstime frame_time, uint16_t *values, uint16_t *num_values,
 
 		/* reset bit guessing state machine if the channel index is out of bounds */
 		if (channel > DSM_MAX_CHANNEL_COUNT) {
+			PX4_DEBUG("channel %d > %d (DSM_MAX_CHANNEL_COUNT)", channel, DSM_MAX_CHANNEL_COUNT);
 			dsm_guess_format(true);
 			return false;
 		}
@@ -645,16 +651,6 @@ bool dsm_decode(hrt_abstime frame_time, uint16_t *values, uint16_t *num_values,
 		values[channel] = value;
 	}
 
-	/*
-	 * Spektrum likes to send junk in higher channel numbers to fill
-	 * their packets. We don't know about a 13 channel model in their TX
-	 * lines, so if we get a channel count of 13, we'll return 12 (the last
-	 * data index that is stable).
-	 */
-	if (*num_values == 13) {
-		*num_values = 12;
-	}
-
 	/* Set the 11-bit data indicator */
 	*dsm_11_bit = (dsm_channel_shift == 11);
 
@@ -845,11 +841,18 @@ bool dsm_parse(const uint64_t now, const uint8_t *frame, const unsigned len, uin
 	}
 
 	if (decode_ret) {
-		*num_values = dsm_chan_count;
+		// require stable channel count (dsm_chan_count == dsm_chan_count_prev) before considering the decode valid
+		if ((dsm_chan_count > 0) && (dsm_chan_count <= DSM_MAX_CHANNEL_COUNT) && (dsm_chan_count == dsm_chan_count_prev)) {
+			*num_values = dsm_chan_count;
+			memcpy(&values[0], &dsm_chan_buf[0], dsm_chan_count * sizeof(dsm_chan_buf[0]));
+
+		} else {
+			decode_ret = false;
+		}
+
+		dsm_chan_count_prev = dsm_chan_count;
 
-		memcpy(&values[0], &dsm_chan_buf[0], dsm_chan_count * sizeof(dsm_chan_buf[0]));
 #ifdef DSM_DEBUG
-
 		printf("PACKET ---------\n");
 		printf("frame drops: %u, chan #: %u\n", dsm_frame_drops, dsm_chan_count);
 

src/lib/rc/rc_tests/RCTest.cpp

@@ -231,17 +231,17 @@ bool RCTest::ghstTest()
 
 bool RCTest::dsmTest10Ch()
 {
-	return dsmTest(TEST_DATA_PATH "dsm_x_data.txt", 10, 6, 1500);
+	return dsmTest(TEST_DATA_PATH "dsm_x_data.txt", 10, 17, 1500);
 }
 
 bool RCTest::dsmTest16Ch()
 {
-	return dsmTest(TEST_DATA_PATH "dsm_x_dx9_data.txt", 16, 3, 1500);
+	return dsmTest(TEST_DATA_PATH "dsm_x_dx9_data.txt", 16, 6, 1500);
 }
 
 bool RCTest::dsmTest22msDSMX16Ch()
 {
-	return dsmTest(TEST_DATA_PATH "dsm_x_dx9_px4_binding_data.txt", 16, 6, 1499);
+	return dsmTest(TEST_DATA_PATH "dsm_x_dx9_px4_binding_data.txt", 16, 11, 1499);
 }
 
 bool RCTest::dsmTest(const char *filepath, unsigned expected_chancount, unsigned expected_dropcount, unsigned chan0)
@@ -290,7 +290,7 @@ bool RCTest::dsmTest(const char *filepath, unsigned expected_chancount, unsigned
 					&dsm_11_bit, &dsm_frame_drops, nullptr, max_channels);
 
 		if (result) {
-			if (count > (16 * 10)) { // need to process enough data to have full channel count
+			if (count > (16 * 20)) { // need to process enough data to have full channel count
 				ut_compare("num_values == expected_chancount", num_values, expected_chancount);
 			}
 
@@ -313,6 +313,8 @@ bool RCTest::dsmTest(const char *filepath, unsigned expected_chancount, unsigned
 
 	fclose(fp);
 
+	ut_compare("num_values == expected_chancount", num_values, expected_chancount);
+
 	ut_test(ret == EOF);
 	//PX4_INFO("drop: %d", (int)last_drop);
 	ut_compare("last_drop == expected_dropcount", last_drop, expected_dropcount);