diff --git a/libraries/AP_HAL_F4Light/RCInput.cpp b/libraries/AP_HAL_F4Light/RCInput.cpp
index e426d1c163..1213b4d014 100644
--- a/libraries/AP_HAL_F4Light/RCInput.cpp
+++ b/libraries/AP_HAL_F4Light/RCInput.cpp
@@ -274,7 +274,9 @@ uint16_t RCInput::read(uint8_t ch)
             
             if(!fs_flag) {
                 fs_flag=true;
+#ifdef DEBUG_BUILD
                 printf("\n failsafe! now=%lld last pulse=%lld last change=%lld\n",now, pulse, last);
+#endif
             }
         } else {
             fs_flag=false;
@@ -288,7 +290,9 @@ uint16_t RCInput::read(uint8_t ch)
             if(last_4 < 990 && data >1300 && data < 1700){
                 if(!aibao_fs_flag){
                     aibao_fs_flag=true;
+#ifdef DEBUG_BUILD
                     printf("\nAibao failsafe! ch4=%d ch2=%d\n",last_4, data);
+#endif
                 }
                 data = 901; // to know the source
             } else {
diff --git a/libraries/AP_HAL_F4Light/RCOutput.cpp b/libraries/AP_HAL_F4Light/RCOutput.cpp
index b45b56720d..5676c84652 100644
--- a/libraries/AP_HAL_F4Light/RCOutput.cpp
+++ b/libraries/AP_HAL_F4Light/RCOutput.cpp
@@ -23,6 +23,37 @@ using namespace F4Light;
 
 #define F4Light_OUT_CHANNELS 6 // motor's channels enabled by default
 
+
+#ifndef SERVO_PIN_5
+ #define SERVO_PIN_5 ((uint8_t)-1)
+#endif
+
+#ifndef SERVO_PIN_6
+ #define SERVO_PIN_6 ((uint8_t)-1)
+#endif
+
+#ifndef SERVO_PIN_7
+ #define SERVO_PIN_7 ((uint8_t)-1)
+#endif
+
+#ifndef SERVO_PIN_8
+ #define SERVO_PIN_8 ((uint8_t)-1)
+#endif
+
+#ifndef SERVO_PIN_9
+ #define SERVO_PIN_9 ((uint8_t)-1)
+#endif
+
+#ifndef SERVO_PIN_10
+ #define SERVO_PIN_10 ((uint8_t)-1)
+#endif
+
+#ifndef SERVO_PIN_11
+ #define SERVO_PIN_11 ((uint8_t)-1)
+#endif
+
+
+
 // #if FRAME_CONFIG == QUAD_FRAME // this is only QUAD layouts
 
 // ArduCopter
@@ -31,20 +62,15 @@ static const uint8_t output_channels_arducopter[]= {  // pin assignment
     SERVO_PIN_2, //Timer3/4  - 2
     SERVO_PIN_3, //Timer2/3  - 3
     SERVO_PIN_4, //Timer2/2  - 4
-#ifdef SERVO_PIN_5
-    SERVO_PIN_5, //Timer2/1
-#endif
-#ifdef SERVO_PIN_6
-    SERVO_PIN_6, //Timer2/0
-#endif
+    SERVO_PIN_5, 
+    SERVO_PIN_6,
 
     // servo channels on input port
-    4, // PB14  CH1_IN - PPM1 Use this channels asd servo only if you use DSM via UART as RC
-    5, // PB15  CH2_IN - PPM2 
-    12, // PC6  CH3_IN UART6
-    13, // PC7  CH4_IN UART6
-    14, // PC8  CH5_IN i2c
-    15, // PC9  CH6_IN i2c
+    SERVO_PIN_7, // PB15  CH2_IN - PPM2 
+    SERVO_PIN_8, // PC6  CH3_IN UART6
+    SERVO_PIN_9, // PC7  CH4_IN UART6
+    SERVO_PIN_10, // PC8  CH5_IN i2c
+    SERVO_PIN_11, // PC9  CH6_IN i2c
 };
 
 
@@ -56,20 +82,15 @@ static const uint8_t output_channels_openpilot[]= {  // pin assignment
     SERVO_PIN_4, //Timer2/2  - 4
     SERVO_PIN_1, //Timer3/3  - 1
     SERVO_PIN_3, //Timer2/3  - 3
-#ifdef SERVO_PIN_5
     SERVO_PIN_5, //Timer2/1
-#endif
-#ifdef SERVO_PIN_6
     SERVO_PIN_6, //Timer2/0
-#endif
 
     // servo channels on input port
-//    4, // PB14  CH1_IN - PPM1 Use this channels asd servo only if you use DSM via UART as RC
-    5, // PB15  CH2_IN - PPM2 
-    12, // PC6  CH3_IN UART6
-    13, // PC7  CH4_IN UART6
-    14, // PC8  CH5_IN i2c
-    15, // PC9  CH6_IN i2c
+    SERVO_PIN_7, // PB15  CH2_IN - PPM2 
+    SERVO_PIN_8, // PC6  CH3_IN UART6
+    SERVO_PIN_9, // PC7  CH4_IN UART6
+    SERVO_PIN_10, // PC8  CH5_IN i2c
+    SERVO_PIN_11, // PC9  CH6_IN i2c
 };
 
 
@@ -79,43 +100,32 @@ static const uint8_t output_channels_cleanflight[]= {  // pin assignment
     SERVO_PIN_3, //Timer2/3  - 3
     SERVO_PIN_4, //Timer2/2  - 4
     SERVO_PIN_1, //Timer3/3  - 1
-#ifdef SERVO_PIN_5
     SERVO_PIN_5, //Timer2/1
-#endif
-#ifdef SERVO_PIN_6
     SERVO_PIN_6, //Timer2/0
-#endif
 
     // servo channels on input port
-//    4, // PB14  CH1_IN - PPM1 Use this channels asd servo only if you use DSM via UART as RC
-    5, // PB15  CH2_IN - PPM2 
-    12, // PC6  CH3_IN UART6
-    13, // PC7  CH4_IN UART6
-    14, // PC8  CH5_IN i2c
-    15, // PC9  CH6_IN i2c
-
+    SERVO_PIN_7, // PB15  CH2_IN - PPM2 
+    SERVO_PIN_8, // PC6  CH3_IN UART6
+    SERVO_PIN_9, // PC7  CH4_IN UART6
+    SERVO_PIN_10, // PC8  CH5_IN i2c
+    SERVO_PIN_11, // PC9  CH6_IN i2c
 };
 
-// Arducopter,shifted 2 pins right to use up to 2 servos
+// Arducopter, shifted 2 pins right to use up to 2 servos
 static const uint8_t output_channels_servo[]= {  // pin assignment
     SERVO_PIN_3, //Timer2/3  - 1
     SERVO_PIN_4, //Timer2/2  - 2
-#ifdef SERVO_PIN_5
     SERVO_PIN_5, //Timer2/1  - 3
-#endif
-#ifdef SERVO_PIN_6
     SERVO_PIN_6, //Timer2/0  - 4
-#endif
     SERVO_PIN_1, //Timer3/3    servo1
     SERVO_PIN_2, //Timer3/4    servo2
 
     // servo channels on input port
-//    4, // PB14  CH1_IN - PPM1 Use this channels as servo only if you use DSM via UART as RC
-    5, // PB15  CH2_IN - PPM2 
-    12, // PC6  CH3_IN UART6
-    13, // PC7  CH4_IN UART6
-    14, // PC8  CH5_IN i2c
-    15, // PC9  CH6_IN i2c
+    SERVO_PIN_7, // PB15  CH2_IN - PPM2 
+    SERVO_PIN_8, // PC6  CH3_IN UART6
+    SERVO_PIN_9, // PC7  CH4_IN UART6
+    SERVO_PIN_10, // PC8  CH5_IN i2c
+    SERVO_PIN_11, // PC9  CH6_IN i2c
 };
 
 
@@ -176,29 +186,6 @@ void RCOutput::do_4way_if(AP_HAL::UARTDriver* uart) {
     esc4wayProcess(uart);
 }
 
-#ifdef DEBUG_INT
-extern "C" int printf(const char *msg, ...);
-
-static void isr_handler(){
-    uint32_t *sp;
-
-#define FRAME_SHIFT 10 // uses IRQ handler itself
-
-    asm volatile ("mov %0, sp\n\t"  : "=rm" (sp) );
-    
-    // Stack frame contains:
-    // r0, r1, r2, r3, r12, r14, the return address and xPSR
-    // - Stacked R0  = sp[0]
-    // - Stacked R1  = sp[1]
-    // - Stacked R2  = sp[2]
-    // - Stacked R3  = sp[3]
-    // - Stacked R12 = sp[4]
-    // - Stacked LR  = sp[5]
-    // - Stacked PC  = sp[6]
-    // - Stacked xPSR= sp[7]
-    printf("pc=%lx lr=%lx\n", sp[FRAME_SHIFT+6], sp[FRAME_SHIFT+5]);
-}
-#endif
 
 void RCOutput::lateInit(){ // 2nd stage with loaded parameters
 
@@ -210,14 +197,6 @@ void RCOutput::lateInit(){ // 2nd stage with loaded parameters
     output_channels = revo_motor_map[map];
     
     InitPWM();
-    
-#ifdef DEBUG_INT
-    uint8_t spin = output_channels[DEBUG_INT]; // motor 6 as button
-    GPIO::_pinMode(spin, INPUT_PULLUP);
-
-    Revo_handler h = { .vp = isr_handler  };  
-    GPIO::_attach_interrupt(spin, h.h, FALLING, 0);
-#endif
 }
 
 void RCOutput::InitPWM()
@@ -635,12 +614,6 @@ void RCOutput::enable_ch(uint8_t ch)
     }
 
     fill_timers(); // re-calculate list of used timers
-
-#ifdef DEBUG_INT
-    uint8_t spin = output_channels[DEBUG_INT]; // motor 6
-    GPIO::_pinMode(spin, INPUT_PULLUP);
-#endif
-    
 }
 
 void RCOutput::disable_ch(uint8_t ch)
diff --git a/libraries/AP_HAL_F4Light/boards/f4light_MatekF405_CTR/board.cpp b/libraries/AP_HAL_F4Light/boards/f4light_MatekF405_CTR/board.cpp
index f058d92f71..fb3fad8dbd 100644
--- a/libraries/AP_HAL_F4Light/boards/f4light_MatekF405_CTR/board.cpp
+++ b/libraries/AP_HAL_F4Light/boards/f4light_MatekF405_CTR/board.cpp
@@ -151,18 +151,6 @@ extern const struct TIM_Channel PWM_Channels[] __FLASH__ =   {
     { // 1 RC_IN2
 	.pin         = PA2, // UART2 TX
     },
-    { // 2 RC_IN3
-	.pin         = (uint8_t)-1,
-    },
-    { // 3 RC_IN4
-	.pin         = (uint8_t)-1,
-    },
-    { // 4 RC_IN5
-	.pin         = (uint8_t)-1,
-    },
-    { // 5 RC_IN6
-	.pin         = (uint8_t)-1,
-    },
 };
 
 
diff --git a/libraries/AP_HAL_F4Light/boards/f4light_Revolution/board.h b/libraries/AP_HAL_F4Light/boards/f4light_Revolution/board.h
index 443bc119d7..2c3e620fd6 100644
--- a/libraries/AP_HAL_F4Light/boards/f4light_Revolution/board.h
+++ b/libraries/AP_HAL_F4Light/boards/f4light_Revolution/board.h
@@ -178,6 +178,13 @@
 #define SERVO_PIN_5 48 // PA1
 #define SERVO_PIN_6 47 // PA0
 
+// input pins as servo outputs
+#define SERVO_PIN_7    5, // PB15  CH2_IN - PPM2 
+#define SERVO_PIN_8   12, // PC6  CH3_IN UART6
+#define SERVO_PIN_9   13, // PC7  CH4_IN UART6
+#define SERVO_PIN_10  14, // PC8  CH5_IN i2c
+#define SERVO_PIN_11  15, // PC9  CH6_IN i2c
+
 #define MOTOR_LAYOUT_DEFAULT 0
 
 #define USE_SERIAL_4WAY_BLHELI_INTERFACE
diff --git a/libraries/AP_HAL_F4Light/boards/f4light_Revolution_EE128/board.h b/libraries/AP_HAL_F4Light/boards/f4light_Revolution_EE128/board.h
index 1908679315..c703fb420d 100644
--- a/libraries/AP_HAL_F4Light/boards/f4light_Revolution_EE128/board.h
+++ b/libraries/AP_HAL_F4Light/boards/f4light_Revolution_EE128/board.h
@@ -184,6 +184,12 @@
 #define SERVO_PIN_5 48 // PA1
 #define SERVO_PIN_6 47 // PA0
 
+// input pins as servo outputs
+#define SERVO_PIN_7    5, // PB15  CH2_IN - PPM2 
+#define SERVO_PIN_8   12, // PC6  CH3_IN UART6
+#define SERVO_PIN_9   13, // PC7  CH4_IN UART6
+#define SERVO_PIN_10  14, // PC8  CH5_IN i2c
+#define SERVO_PIN_11  15, // PC9  CH6_IN i2c
 #define MOTOR_LAYOUT_DEFAULT 0
 
 #define USE_SERIAL_4WAY_BLHELI_INTERFACE
diff --git a/libraries/AP_HAL_F4Light/boards/f4light_Revolution_SD/board.h b/libraries/AP_HAL_F4Light/boards/f4light_Revolution_SD/board.h
index 85b63d51c5..d9e735d503 100644
--- a/libraries/AP_HAL_F4Light/boards/f4light_Revolution_SD/board.h
+++ b/libraries/AP_HAL_F4Light/boards/f4light_Revolution_SD/board.h
@@ -179,6 +179,13 @@
 #define SERVO_PIN_5 48 // PA1
 #define SERVO_PIN_6 47 // PA0
 
+// input pins as servo outputs
+#define SERVO_PIN_7    5, // PB15  CH2_IN - PPM2 
+#define SERVO_PIN_8   12, // PC6  CH3_IN UART6
+#define SERVO_PIN_9   13, // PC7  CH4_IN UART6
+#define SERVO_PIN_10  14, // PC8  CH5_IN i2c
+#define SERVO_PIN_11  15, // PC9  CH6_IN i2c
+
 #define MOTOR_LAYOUT_DEFAULT 0
 
 #define USE_SERIAL_4WAY_BLHELI_INTERFACE
diff --git a/libraries/AP_HAL_F4Light/hardware/hal/syscalls.c b/libraries/AP_HAL_F4Light/hardware/hal/syscalls.c
index 5eb580ec5b..483f43843c 100644
--- a/libraries/AP_HAL_F4Light/hardware/hal/syscalls.c
+++ b/libraries/AP_HAL_F4Light/hardware/hal/syscalls.c
@@ -39,7 +39,7 @@ based on:
 #include <syscalls.h>
 #include <systick.h>
 
-/* _end and _eccm is set in the linker command file */
+/* _end and _eccm are set in the linker command file */
 extern caddr_t _end;
 extern caddr_t _eccm;
 
@@ -63,7 +63,7 @@ int _getpid(void)
 
 
 /*
- * sbrk -- changes heap size size. Get nbytes more
+ * sbrk -- changes heap size. Get nbytes more
  *         RAM. We just increment a pointer in what's
  *         left of memory on the board.
  */
@@ -108,8 +108,7 @@ static caddr_t _sbrk_ccm(int nbytes) {
 
     if(stack_bottom) top = (uint32_t)stack_bottom;
 
-    if ( top > (unsigned int)heap_ptr+nbytes) // there is place in stack, if stack in RAM it will be true too
-    {
+    if ( top > (unsigned int)heap_ptr+nbytes) {// there is place in stack, if stack in RAM it will be true too
         base = heap_ptr;
         heap_ptr += nbytes;
         __brkval_ccm = heap_ptr;
@@ -126,8 +125,7 @@ caddr_t sbrk_ccm(int nbytes) {
 
 
 caddr_t _sbrk(int nbytes) {
-    return _sbrk_ram(nbytes);
-    
+    return _sbrk_ram(nbytes);    
 }
 
 
diff --git a/libraries/AP_HAL_F4Light/hardware/hal/systick.c b/libraries/AP_HAL_F4Light/hardware/hal/systick.c
index 80ae7f2d93..b34d5d8c5b 100644
--- a/libraries/AP_HAL_F4Light/hardware/hal/systick.c
+++ b/libraries/AP_HAL_F4Light/hardware/hal/systick.c
@@ -135,7 +135,6 @@ extern void hal_go_next_task();
 #define NVIC_CCR (*(volatile uint32_t *)0xE000ED14)
 
 // new common exception code
-// TODO: we have task switching so if fault occures in task we can just remove task from queue
 //
 void __attribute__((noreturn)) __error(uint32_t num, uint32_t pc, uint32_t lr, uint32_t flag)
 {
@@ -191,32 +190,16 @@ void __attribute__((noreturn)) __error(uint32_t num, uint32_t pc, uint32_t lr, u
 
     hal_stop_multitask();
 
-#if 0
- #ifdef ERROR_USART
-    usart_putstr(ERROR_USART, "\r\n!!! Exception: ");
-  #ifdef DEBUG_BUILD
-    usart_putstr(ERROR_USART, faults[num]);
-  #else
-    usart_putudec(ERROR_USART, num);
-  #endif
-    usart_putstr(ERROR_USART, " at ");
-    usart_putudec(ERROR_USART, pc);
-    usart_putstr(ERROR_USART, " lr ");
-    usart_putudec(ERROR_USART, lr);
-    usart_putc(ERROR_USART, '\n');
-    usart_putc(ERROR_USART, '\r');
- #endif
-#else
- #ifdef DEBUG_BUILD
+#ifdef DEBUG_BUILD
     printf("\r\n!!! Exception: %s at %x LR=%x\n",faults[num], pc, lr);
- #else
+#else
     printf("\r\n!!! Exception: %d at %x LR=%x\n",num, pc, lr);
- #endif
 #endif
     error_throb(num);
 }
 
-#if 0 
+#if 0 // not removed for case if something will require Timer5
+
 uint32_t systick_micros(void)
 {
     volatile uint32_t fms, lms;