Another take on Spektrum/DSM frame decoding, based on more careful examination of the relevant docs.

2026-11-02 02:51:37 +08:00 · 2012-11-07 02:47:01 -08:00
parent 7d76a8a57b
commit ff3a014971
8 changed files with 377 additions and 213 deletions
@@ -44,6 +44,7 @@
 #include <debug.h>
 #include <stdlib.h>
 #include <errno.h>
+#include <termios.h>
 #include <string.h>
 #include <poll.h>

@@ -60,26 +61,126 @@

 static int			fmu_fd;
 static hx_stream_t		stream;
-
+static int			rx_fd;
 static struct px4io_report	report;

 static void			comms_handle_frame(void *arg, const void *buffer, size_t length);

+static struct pollfd pollfds[2];
+static int pollcount;
+
 void
 comms_init(void)
 {
+	/* initialise the FMU interface */
 	fmu_fd = open("/dev/ttyS1", O_RDWR | O_NONBLOCK);
 	if (fmu_fd < 0)
 		lib_lowprintf("COMMS: fmu open failed %d\n", errno);
-
 	stream = hx_stream_init(fmu_fd, comms_handle_frame, NULL);
+	pollfds[0].fd = fmu_fd;
+	pollfds[0].events = POLLIN;
+	pollcount = 1;

+	/* default state in the report to FMU */
 	report.i2f_magic = I2F_MAGIC;
+
+}
+
+static void
+serial_rx_init(unsigned serial_mode)
+{
+	if (serial_mode == system_state.serial_rx_mode)
+		return;
+	system_state.serial_rx_mode = serial_mode;
+
+	if (serial_mode == RX_MODE_PPM_ONLY) {
+		if (rx_fd != -1) {
+			pollcount = 1;
+			close(rx_fd);
+			rx_fd = -1;
+		}
+		return;
+	}
+
+	/* open the serial port used for DSM and S.bus communication */
+	rx_fd = open("/dev/ttyS0", O_RDONLY | O_NONBLOCK);
+	pollfds[1].fd = rx_fd;
+	pollfds[1].events = POLLIN;
+	pollcount = 2;
+
+	struct termios t;
+	tcgetattr(rx_fd, &t);
+
+	switch (serial_mode) {
+	case RX_MODE_DSM_10BIT:
+	case RX_MODE_DSM_11BIT:
+
+		/* 115200, no parity, one stop bit */
+		cfsetspeed(&t, 115200);
+		t.c_cflag &= ~(CSTOPB | PARENB);
+
+		dsm_init(serial_mode);
+		break;
+
+	case RX_MODE_FUTABA_SBUS:
+		/* 100000, even parity, two stop bits */
+		cfsetspeed(&t, 100000);
+		t.c_cflag |= (CSTOPB | PARENB);
+
+		sbus_init(serial_mode);
+		break;
+
+	default:
+		break;
+	}
+
+	tcsetattr(rx_fd, TCSANOW, &t);
 }

 void
 comms_check(void)
 {
+	/*
+	 * Check for serial data
+	 */
+	int ret = poll(pollfds, pollcount, 0);
+
+	if (ret > 0) {
+		/*
+		 * Pull bytes from FMU and feed them to the HX engine.
+		 * Limit the number of bytes we actually process on any one iteration.
+		 */
+		if (pollfds[0].revents & POLLIN) {
+			char buf[32];
+			ssize_t count = read(fmu_fd, buf, sizeof(buf));
+			for (int i = 0; i < count; i++)
+				hx_stream_rx(stream, buf[i]);
+		}
+
+		/*
+		 * Pull bytes from the serial RX port and feed them to the decoder
+		 * if we care about serial RX data.
+		 */
+		if ((pollcount > 1) && (pollfds[1].revents & POLLIN)) {
+			switch (system_state.serial_rx_mode) {
+			case RX_MODE_DSM_10BIT:
+			case RX_MODE_DSM_11BIT:
+				dsm_input(rx_fd);
+				break;
+
+			case RX_MODE_FUTABA_SBUS:
+				sbus_input(rx_fd);
+				break;
+
+			default:
+				break;
+			}
+		}
+	}
+
+	/*
+	 * Decide if it's time to send an update to the FMU.
+	 */
 	static hrt_abstime last_report_time;
 	hrt_abstime now, delta;

@@ -87,7 +188,7 @@ comms_check(void)
 	now = hrt_absolute_time();
 	delta = now - last_report_time;
 	if ((delta > FMU_MIN_REPORT_INTERVAL) && 
-		(system_state.fmu_report_due || (delta > FMU_MAX_REPORT_INTERVAL))) {
+	    (system_state.fmu_report_due || (delta > FMU_MAX_REPORT_INTERVAL))) {

 		system_state.fmu_report_due = false;
 		last_report_time = now;
@@ -101,15 +202,6 @@ comms_check(void)
 		/* and send it */
 		hx_stream_send(stream, &report, sizeof(report));
 	}
-
-	/*
-	 * Check for bytes and feed them to the RX engine.  
-	 * Limit the number of bytes we actually process on any one iteration.
-	 */
-	char buf[32];
-	ssize_t count = read(fmu_fd, buf, sizeof(buf));
-	for (int i = 0; i < count; i++)
-		hx_stream_rx(stream, buf[i]);
 }

 int frame_rx;
@@ -127,8 +219,7 @@ comms_handle_config(const void *buffer, size_t length)

 	frame_rx++;

-	mixer_set_serial_mode(cfg->serial_rx_mode);
-
+	serial_rx_init(cfg->serial_rx_mode);
 }

 static void