px4iofirmware: support setting the SBUS output frame rate

this allows for helicopters and multicopters with SBUS output

src/modules/px4iofirmware/protocol.h

@@ -239,6 +239,8 @@ enum {							/* DSM bind states */
 #define PX4IO_P_SETUP_TRIM_PITCH		17	/**< Pitch trim, in actuator units */
 #define PX4IO_P_SETUP_TRIM_YAW			18	/**< Yaw trim, in actuator units */
 
+#define PX4IO_P_SETUP_SBUS_RATE			19	/* frame rate of SBUS1 output in Hz */
+
 /* autopilot control values, -10000..10000 */
 #define PX4IO_PAGE_CONTROLS			51	/**< actuator control groups, one after the other, 8 wide */
 #define PX4IO_P_CONTROLS_GROUP_0		(PX4IO_PROTOCOL_MAX_CONTROL_COUNT * 0)	/**< 0..PX4IO_PROTOCOL_MAX_CONTROL_COUNT - 1 */

src/modules/px4iofirmware/px4io.h

@@ -122,6 +122,7 @@ extern uint16_t			r_page_servo_disarmed[];	/* PX4IO_PAGE_DISARMED_PWM */
 #define r_setup_trim_roll	r_page_setup[PX4IO_P_SETUP_TRIM_ROLL]
 #define r_setup_trim_pitch	r_page_setup[PX4IO_P_SETUP_TRIM_PITCH]
 #define r_setup_trim_yaw	r_page_setup[PX4IO_P_SETUP_TRIM_YAW]
+#define r_setup_sbus_rate	r_page_setup[PX4IO_P_SETUP_SBUS_RATE]
 
 #define r_control_values	(&r_page_controls[0])
 

src/modules/px4iofirmware/registers.c

@@ -48,6 +48,7 @@
 #include <systemlib/systemlib.h>
 #include <stm32_pwr.h>
 #include <rc/dsm.h>
+#include <rc/sbus.h>
 
 #include "px4io.h"
 #include "protocol.h"
@@ -157,6 +158,7 @@ volatile uint16_t	r_page_setup[] = {
 	[PX4IO_P_SETUP_PWM_RATES]		= 0,
 	[PX4IO_P_SETUP_PWM_DEFAULTRATE]		= 50,
 	[PX4IO_P_SETUP_PWM_ALTRATE]		= 200,
+	[PX4IO_P_SETUP_SBUS_RATE]		= 72,
 #ifdef CONFIG_ARCH_BOARD_PX4IO_V1
 	[PX4IO_P_SETUP_RELAYS]			= 0,
 #else
@@ -682,6 +684,10 @@ registers_set_one(uint8_t page, uint8_t offset, uint16_t value)
 			r_page_setup[offset] = value;
 			break;
 
+		case PX4IO_P_SETUP_SBUS_RATE:
+			sbus1_set_output_rate_hz(value);
+			break;
+
 		default:
 			return -1;
 		}