RC C library: Use same buffer as the protocols do not decode in parallel.

src/lib/rc/CMakeLists.txt

@@ -35,10 +35,11 @@ px4_add_module(
 	COMPILE_FLAGS
 		-Wno-unused-result
 	SRCS
-		st24.c
-		sumd.c
-		sbus.c
-		dsm.c
+		st24.cpp
+		sumd.cpp
+		sbus.cpp
+		dsm.cpp
+		common_rc.cpp
 	DEPENDS
 		platforms__common
 	)

src/lib/rc/common_rc.cpp

@@ -0,0 +1,4 @@
+
+#include "common_rc.h"
+
+__EXPORT rc_decode_buf_t rc_decode_buf;

src/lib/rc/common_rc.h

@@ -0,0 +1,33 @@
+
+#pragma once
+
+#include <stdint.h>
+
+#include "dsm.h"
+#include "sbus.h"
+#include "st24.h"
+#include "sumd.h"
+#include "dsm.h"
+
+#pragma pack(push, 1)
+typedef   uint8_t dsm_frame_t[DSM_BUFFER_SIZE]; /**< DSM dsm frame receive buffer */
+typedef   uint8_t dsm_buf_t[DSM_FRAME_SIZE * 2]; // Define working buffer
+
+typedef  struct dsm_decode_t {
+	dsm_frame_t frame;
+	dsm_buf_t buf;
+} dsm_decode_t;
+
+typedef   uint8_t sbus_frame_t[SBUS_FRAME_SIZE + (SBUS_FRAME_SIZE / 2)];
+
+typedef  struct rc_decode_buf_ {
+	union {
+		dsm_decode_t dsm;
+		sbus_frame_t sbus_frame;
+		ReceiverFcPacket _strxpacket;
+		ReceiverFcPacketHoTT _hottrxpacket;
+	};
+} rc_decode_buf_t;
+#pragma pack(pop)
+
+extern rc_decode_buf_t rc_decode_buf;

src/lib/rc/dsm.cpp

@@ -32,7 +32,7 @@
  ****************************************************************************/
 
 /**
- * @file dsm.c
+ * @file dsm.cpp
  *
  * Serial protocol decoder for the Spektrum DSM* family of protocols.
  *
@@ -49,6 +49,7 @@
 #include <string.h>
 
 #include "dsm.h"
+#include "common_rc.h"
 #include <drivers/drv_hrt.h>
 
 #if defined (__PX4_LINUX) || defined (__PX4_DARWIN) || defined(__PX4_QURT)
@@ -68,8 +69,9 @@ static enum DSM_DECODE_STATE {
 static int dsm_fd = -1;						/**< File handle to the DSM UART */
 static hrt_abstime dsm_last_rx_time;            /**< Timestamp when we last received data */
 static hrt_abstime dsm_last_frame_time;		/**< Timestamp for start of last valid dsm frame */
-static uint8_t dsm_frame[DSM_BUFFER_SIZE];	/**< DSM dsm frame receive buffer */
-static uint8_t dsm_buf[DSM_FRAME_SIZE * 2];
+static dsm_frame_t &dsm_frame = rc_decode_buf.dsm.frame;	/**< DSM_BUFFER_SIZE DSM dsm frame receive buffer */
+static dsm_buf_t &dsm_buf = rc_decode_buf.dsm.buf;	/**< DSM_BUFFER_SIZE DSM dsm frame receive buffer */
+
 static uint16_t dsm_chan_buf[DSM_MAX_CHANNEL_COUNT];
 static unsigned dsm_partial_frame_count;	/**< Count of bytes received for current dsm frame */
 static unsigned dsm_channel_shift = 0;			/**< Channel resolution, 0=unknown, 1=10 bit, 2=11 bit */

src/lib/rc/sbus.cpp

@@ -49,6 +49,7 @@
 #endif
 
 #include "sbus.h"
+#include "common_rc.h"
 #include <drivers/drv_hrt.h>
 
 #define SBUS_DEBUG_LEVEL 	0 /* Set debug output level */
@@ -116,7 +117,7 @@ static enum SBUS2_DECODE_STATE {
 	SBUS2_DECODE_STATE_SBUS2_DATA2 = 0x34
 } sbus_decode_state = SBUS2_DECODE_STATE_DESYNC;
 
-static uint8_t	sbus_frame[SBUS_FRAME_SIZE + (SBUS_FRAME_SIZE / 2)];
+static sbus_frame_t	 &sbus_frame = rc_decode_buf.sbus_frame;
 
 static unsigned partial_frame_count;
 static unsigned sbus1_frame_delay = (1000U * 1000U) / SBUS1_DEFAULT_RATE_HZ;

src/lib/rc/st24.cpp

@@ -42,6 +42,7 @@
 #include <stdbool.h>
 #include <stdio.h>
 #include "st24.h"
+#include "common_rc.h"
 
 enum ST24_DECODE_STATE {
 	ST24_DECODE_STATE_UNSYNCED = 0,
@@ -74,7 +75,7 @@ const char *decode_states[] = {"UNSYNCED",
 static enum ST24_DECODE_STATE _decode_state = ST24_DECODE_STATE_UNSYNCED;
 static uint8_t _rxlen;
 
-static ReceiverFcPacket _rxpacket;
+static ReceiverFcPacket &_rxpacket = rc_decode_buf._strxpacket;
 
 uint8_t st24_common_crc8(uint8_t *ptr, uint8_t len)
 {

src/lib/rc/sumd.cpp

@@ -42,7 +42,7 @@
 #include <stdbool.h>
 #include <stdio.h>
 #include "sumd.h"
-
+#include "common_rc.h"
 
 enum SUMD_DECODE_STATE {
 	SUMD_DECODE_STATE_UNSYNCED = 0,
@@ -88,8 +88,7 @@ bool		_debug		= false;
 static enum SUMD_DECODE_STATE _decode_state = SUMD_DECODE_STATE_UNSYNCED;
 static uint8_t _rxlen;
 
-static ReceiverFcPacketHoTT _rxpacket;
-
+static ReceiverFcPacketHoTT &_rxpacket = rc_decode_buf._hottrxpacket;
 
 uint16_t sumd_crc16(uint16_t crc, uint8_t value)
 {