AP_HAL_Linux: RCOutput_Navio: allow to have other OE pin

While at it also rename enable_pin to follow the convention of starting
with underscore for private members.

libraries/AP_HAL_Linux/HAL_Linux_Class.cpp

@@ -94,7 +94,7 @@ static LinuxRCOutput_AioPRU rcoutDriver;
   use the PCA9685 based RCOutput driver on Navio
  */
 #elif CONFIG_HAL_BOARD_SUBTYPE == HAL_BOARD_SUBTYPE_LINUX_NAVIO
-static LinuxRCOutput_Navio rcoutDriver;
+static LinuxRCOutput_Navio rcoutDriver(RPI_GPIO_27);
 #elif CONFIG_HAL_BOARD_SUBTYPE == HAL_BOARD_SUBTYPE_LINUX_ZYNQ
 static LinuxRCOutput_ZYNQ rcoutDriver;
 #elif CONFIG_HAL_BOARD_SUBTYPE == HAL_BOARD_SUBTYPE_LINUX_BEBOP

libraries/AP_HAL_Linux/RCOutput_Navio.cpp

@@ -47,15 +47,15 @@
 using namespace Linux;
 
 #define PWM_CHAN_COUNT 13
-#define PCA9685_OUTPUT_ENABLE RPI_GPIO_27
 
 static const AP_HAL::HAL& hal = AP_HAL_BOARD_DRIVER;
 
-LinuxRCOutput_Navio::LinuxRCOutput_Navio():
+LinuxRCOutput_Navio::LinuxRCOutput_Navio(uint8_t oe_pin_number) :
     _i2c_sem(NULL),
-    enable_pin(NULL),
+    _enable_pin(NULL),
     _frequency(50),
-    _pulses_buffer(new uint16_t[PWM_CHAN_COUNT])
+    _pulses_buffer(new uint16_t[PWM_CHAN_COUNT]),
+    _oe_pin_number(oe_pin_number)
 {
 }
 
@@ -79,9 +79,9 @@ void LinuxRCOutput_Navio::init(void* machtnicht)
     set_freq(0, 50);
 
     /* Enable PCA9685 PWM */
-    enable_pin = hal.gpio->channel(PCA9685_OUTPUT_ENABLE);
-    enable_pin->mode(HAL_GPIO_OUTPUT);
-    enable_pin->write(0);
+    _enable_pin = hal.gpio->channel(_oe_pin_number);
+    _enable_pin->mode(HAL_GPIO_OUTPUT);
+    _enable_pin->write(0);
 }
 
 void LinuxRCOutput_Navio::reset_all_channels()

libraries/AP_HAL_Linux/RCOutput_Navio.h

@@ -6,7 +6,7 @@
 
 class Linux::LinuxRCOutput_Navio : public AP_HAL::RCOutput {
     public:
-    LinuxRCOutput_Navio();
+    LinuxRCOutput_Navio(uint8_t oe_pin_number);
     ~LinuxRCOutput_Navio();
     void     init(void* machtnichts);
     void     reset_all_channels();
@@ -23,10 +23,11 @@ private:
     void reset();
 
     AP_HAL::Semaphore *_i2c_sem;
-    AP_HAL::DigitalSource *enable_pin;
+    AP_HAL::DigitalSource *_enable_pin;
     uint16_t _frequency;
 
     uint16_t *_pulses_buffer;
+    uint8_t _oe_pin_number;
 };
 
 #endif // __AP_HAL_LINUX_RCOUTPUT_NAVIO_H__