代码是使用51汇编写的，读之前，先打开汇编指令文档和EFM8BB2 Reference Manual这两个文档备查。 这个有点干涩，也没有其它人做这样的详细解读，一起一行一行读一下吧。

BLHELI主要是由 一堆.inc文件和 BLHeli_S.asm两个组成。 *.inc主要是定义针脚的布局，然后如何开关各个fet等，这个和主逻辑关系不大，我们先不解读*.inc. 

BLHeli_S.asm 是从pgm_start 开始的, 我们按正常的流程一行一行来读，先走主的流程。

;**** **** **** **** **** **** **** **** **** **** **** **** ****
;**** **** **** **** **** **** **** **** **** **** **** **** ****
;**** **** **** **** **** **** **** **** **** **** **** **** ****
;
; Main program start
;
;**** **** **** **** **** **** **** **** **** **** **** **** ****
;**** **** **** **** **** **** **** **** **** **** **** **** ****
;**** **** **** **** **** **** **** **** **** **** **** **** ****

pgm_start:
	; Initialize flash keys to invalid values
	mov	Flash_Key_1, #0
	mov	Flash_Key_2, #0
	; Disable the WDT.
	mov	WDTCN, #0DEh		; Disable watchdog
	mov	WDTCN, #0ADh		
	; Initialize stack
	mov	SP, #0c0h			; Stack = 64 upper bytes of RAM
	; Initialize VDD monitor
IF MCU_48MHZ < 2
	orl	VDM0CN, #080h    	; Enable the VDD monitor
ENDIF
	mov 	RSTSRC, #06h   	; Set missing clock and VDD monitor as a reset source if not 1S capable
	; Set clock frequency
	mov	CLKSEL, #00h		; Set clock divider to 1
	; Switch power off
	call	switch_power_off
	; Ports initialization
	mov	P0, #P0_INIT
	mov	P0MDIN, #P0_DIGITAL
	mov	P0MDOUT, #P0_PUSHPULL
	mov	P0, #P0_INIT
	mov	P0SKIP, #P0_SKIP				
	mov	P1, #P1_INIT
	mov	P1MDIN, #P1_DIGITAL
	mov	P1MDOUT, #P1_PUSHPULL
	mov	P1, #P1_INIT
	mov	P1SKIP, #P1_SKIP				
	mov	P2MDOUT, #P2_PUSHPULL				
	; Initialize the XBAR and related functionality
	Initialize_Xbar	
	; Switch power off again, after initializing ports
	call	switch_power_off
	; Clear RAM
	clr	A				; Clear accumulator
	mov	Temp1, A			; Clear Temp1
	clear_ram:	
	mov	@Temp1, A			; Clear RAM
	djnz Temp1, clear_ram	; Is A not zero? - jump
	; Set default programmed parameters
	call	set_default_parameters
	; Read all programmed parameters
	call read_all_eeprom_parameters
	; Set beep strength
	mov	Temp1, #Pgm_Beep_Strength
	mov	Beep_Strength, @Temp1
	; Set initial arm variable
	mov	Initial_Arm, #1
	; Initializing beep
	clr	IE_EA			; Disable interrupts explicitly
	call wait200ms	
	call beep_f1
	call wait30ms
	call beep_f2
	call wait30ms
	call beep_f3
	call wait30ms
	call	led_control

这里先做一些初始化， 特别一点这里会操作VDM0CN和RSTSRC，打开VDD电压监控，要是电压变化超过一定的范围，会软重启。

    初始化时钟CLKSEL=0, 表示div 1,  这里先是选择HFOSC0(24.5 MHz)， 即1tick是 1/24.5 ns秒，后面到运行阶段要是48Mhz的MCU就会选择HFOSC1(49 MHz).

    跟着读取配置等等 然后驱动电机响三声，输出一个do re mi 的声音。表示初始化完成。

一共会有四个声调输出，f1, f2,f3,f4, 我们认为是do re mi fa吧。 即do re mi就是f1 f2  f3.

接着检查输入的rc_in, 就是电调的信线连着那个针脚的电平，检查它有没有15ms持续都是高电平，如果是的话，那么跳到bootloader, 就是进入和电脑blsuite设置的功能里。因为如 pwm是20ms一个周期，高电平最多2-3ms， dshot, ppm 等都不可能这么多时间高电平，所以这个15ms是一个很合理的值。

;**** **** **** **** **** **** **** **** **** **** **** **** ****
;
; No signal entry point
;
;**** **** **** **** **** **** **** **** **** **** **** **** ****
init_no_signal:
	; Disable interrupts explicitly
	clr	IE_EA
	; Initialize flash keys to invalid values
	mov	Flash_Key_1, #0
	mov	Flash_Key_2, #0
	; Check if input signal is high for more than 15ms
	mov	Temp1, #250
input_high_check_1:
	mov	Temp2, #250
input_high_check_2:
	jnb	RTX_PORT.RTX_PIN, bootloader_done	; Look for low
	djnz	Temp2, input_high_check_2
	djnz	Temp1, input_high_check_1

IF MCU_48MHZ == 2
	ljmp	0F000h			; Jump to bootloader
ELSE
	ljmp	1C00h			; Jump to bootloader
ENDIF

我们先不看bootloader,  先看正常流程，正常流程是跳到bootloader_done，跳到这里，就是解码之前读出的配置,  然后调用 find_throttle_gains 去找油门补偿，就是根据最大最小测试，还有死区，计算一个油门的补偿，结果放在 Throttle_Gain:    （  ; Gain to be applied to RCP value）和
Throttle_Gain_M:           (  倍数， Gain to be applied to RCP value (multiplier 0=1x, 1=2x, 2=4x etc)) )

bootloader_done:
	; Decode settings
	call	decode_settings
	; Find throttle gain from stored min and max settings
	call	find_throttle_gains
	; Set beep strength
	mov	Temp1, #Pgm_Beep_Strength
	mov	Beep_Strength, @Temp1
	; Switch power off
	call	switch_power_off
	; Set clock frequency
IF MCU_48MHZ >= 1
	Set_MCU_Clk_24MHz
ENDIF

开启油门输入的中断，开启timer等等

; Setup timers for pwm input
	mov	IT01CF, #RTX_PIN	; Route RCP input to INT0
	mov	TCON, #11h		; Timer 0 run and INT0 edge triggered
	mov	CKCON0, #04h		; Timer 0 clock is system clock
	mov	TMOD, #09h		; Timer 0 set to 16bits and gated by INT0
	mov	TMR2CN0, #04h		; Timer 2 enabled
	mov	TMR3CN0, #04h		; Timer 3 enabled
	Initialize_PCA			; Initialize PCA
	Set_Pwm_Polarity		; Set pwm polarity
	Enable_Power_Pwm_Module	; Enable power pwm module
	Enable_Damp_Pwm_Module	; Enable damping pwm module
	; Enable interrupts
IF MCU_48MHZ == 0
	mov	IE, #21h			; Enable timer 2 interrupts and INT0 interrupts
ELSE
	mov	IE, #23h			; Enable timer 0, timer 2 interrupts and INT0 interrupts
ENDIF
	mov	EIE1, #90h		; Enable timer 3 and PCA0 interrupts
	mov	IP, #01h			; High priority to INT0 interrupts

初始化比较器和ADC，并打开所有的中断

	; Initialize comparator
	Initialize_Comparator	; Initialize comparator
	; Initialize ADC
	Initialize_Adc			; Initialize ADC operation
	call	wait1ms
	setb	IE_EA			; Enable all interrupts

重置一些和dshot输入信号相关的变量：

	; Reset stall count
	mov	Stall_Cnt, #0
	; Initialize RC pulse
	clr	Flags2.RCP_UPDATED		 	; Clear updated flag
	call wait200ms
	; Clear all shot flags
	clr	Flags2.RCP_ONESHOT125			; Clear OneShot125 flag
	clr	Flags2.RCP_ONESHOT42			; Clear OneShot42 flag
	clr	Flags2.RCP_MULTISHOT			; Clear Multishot flag
	clr	Flags2.RCP_DSHOT				; Clear DShot flag
	mov 	Dshot_Cmd, #0					; Clear Dshot command
	mov 	Dshot_Cmd_Cnt, #0				; Clear Dshot command count

测试信号是不是常规的pwm， 直接等100ms ，是如果Rcp_Outside_Range_Cnt小于10，那么就是常规的pwm。  否则去检查是不是OneShot125，mulitshot. 检查之前会上面几行已经清空Flags2.RCP_ONESHOT125，  Flags2.RCP_ONESHOT42，clr    Flags2.RCP_MULTISHOT

和clr    Flags2.RCP_DSHOT。

Rcp_Outside_Range的是在输入信号的中断里，检查到高电水大于2235us就会增加一次计数。pwm是20ms一个周期，最多5次，正常一般正电平也不会超2235us。

; Test whether signal is regular pwm
	mov	Rcp_Outside_Range_Cnt, #0		; Reset out of range counter
	call wait100ms						; Wait for new RC pulse
	clr	C
	mov	A, Rcp_Outside_Range_Cnt			; Check how many pulses were outside normal range ("900-2235us")
	subb	A, #10						
	jnc	($+4)   ;jump to Test whether signal is OneShot125 
	ajmp	validate_rcp_start

检查输入出信号是不是dshot, 检查之前设置    Flags2.RCP_ONESHOT125  

	; Test whether signal is OneShot125
	setb	Flags2.RCP_ONESHOT125			; Set OneShot125 flag
	mov	Rcp_Outside_Range_Cnt, #0		; Reset out of range counter
	call wait100ms						; Wait for new RC pulse
	clr	C
	mov	A, Rcp_Outside_Range_Cnt			; Check how many pulses were outside normal range ("900-2235us")
	subb	A, #10
	jnc	($+4)
	ajmp	validate_rcp_start

检查其它信号，这里如下，这里不详细看了, 相关资料

Standard PWM ：1000us – 2000us
Oneshot125：125us – 250us
Oneshot 42：2us – 84us
Multishot：5us – 25us

Dshot150 ：106.8us
Dshot300 ：53.4us
Dshot600 ：26.7us
DShot1200：13.4us

; Test whether signal is OneShot42
	clr	Flags2.RCP_ONESHOT125
	setb	Flags2.RCP_ONESHOT42			; Set OneShot42 flag
	mov	Rcp_Outside_Range_Cnt, #0		; Reset out of range counter
	call wait100ms						; Wait for new RC pulse
	clr	C
	mov	A, Rcp_Outside_Range_Cnt			; Check how many pulses were outside normal range ("900-2235us")
	subb	A, #10
	jnc	($+4)
	ajmp	validate_rcp_start

	; Setup timers for DShot
	mov	IT01CF, #(80h+(RTX_PIN SHL 4)+(RTX_PIN))	; Route RCP input to INT0/1, with INT1 inverted
	mov	TCON, #51h		; Timer 0/1 run and INT0 edge triggered
	mov	CKCON0, #01h		; Timer 0/1 clock is system clock divided by 4 (for DShot150)
	mov	TMOD, #0AAh		; Timer 0/1 set to 8bits auto reload and gated by INT0
	mov	TH0, #0			; Auto reload value zero
	mov	TH1, #0
	; Setup interrupts for DShot
	clr	IE_ET0			; Disable timer 0 interrupts
	setb	IE_ET1			; Enable timer 1 interrupts
	setb	IE_EX1			; Enable int1 interrupts
	; Setup variables for DSshot150
IF MCU_48MHZ >= 1
	mov	DShot_Timer_Preset, #128			; Load DShot sync timer preset (for DShot150)
ELSE
	mov	DShot_Timer_Preset, #192
ENDIF
	mov	DShot_Pwm_Thr, #20				; Load DShot qualification pwm threshold (for DShot150)
	mov	DShot_Frame_Length_Thr, #80		; Load DShot frame length criteria
	; Test whether signal is DShot150
	clr	Flags2.RCP_ONESHOT42
	setb	Flags2.RCP_DSHOT
	mov	Rcp_Outside_Range_Cnt, #10		; Set out of range counter
	call wait100ms						; Wait for new RC pulse
	mov	DShot_Pwm_Thr, #16				; Load DShot regular pwm threshold
	clr	C
	mov	A, Rcp_Outside_Range_Cnt			; Check if pulses were accepted
	subb	A, #10
	mov 	Dshot_Cmd, #0
	mov 	Dshot_Cmd_Cnt, #0
	jc	validate_rcp_start

	; Setup variables for DShot300
	mov	CKCON0, #0Ch					; Timer 0/1 clock is system clock (for DShot300)
IF MCU_48MHZ >= 1
	mov	DShot_Timer_Preset, #0			; Load DShot sync timer preset (for DShot300)
ELSE
	mov	DShot_Timer_Preset, #128
ENDIF
	mov	DShot_Pwm_Thr, #40				; Load DShot qualification pwm threshold (for DShot300)
	mov	DShot_Frame_Length_Thr, #40		; Load DShot frame length criteria
	; Test whether signal is DShot300
	mov	Rcp_Outside_Range_Cnt, #10		; Set out of range counter
	call wait100ms						; Wait for new RC pulse
	mov	DShot_Pwm_Thr, #32				; Load DShot regular pwm threshold
	clr	C
	mov	A, Rcp_Outside_Range_Cnt			; Check if pulses were accepted
	subb	A, #10
	mov 	Dshot_Cmd, #0
	mov 	Dshot_Cmd_Cnt, #0
	jc	validate_rcp_start

	; Setup variables for DShot600
	mov	CKCON0, #0Ch					; Timer 0/1 clock is system clock (for DShot600)
IF MCU_48MHZ >= 1
	mov	DShot_Timer_Preset, #128			; Load DShot sync timer preset (for DShot600)
ELSE
	mov	DShot_Timer_Preset, #192
ENDIF
	mov	DShot_Pwm_Thr, #20				; Load DShot qualification pwm threshold (for DShot600)
	mov	DShot_Frame_Length_Thr, #20		; Load DShot frame length criteria
	; Test whether signal is DShot600
	mov	Rcp_Outside_Range_Cnt, #10		; Set out of range counter
	call wait100ms						; Wait for new RC pulse
	mov	DShot_Pwm_Thr, #16				; Load DShot regular pwm threshold
	clr	C
	mov	A, Rcp_Outside_Range_Cnt			; Check if pulses were accepted
	subb	A, #10
	mov 	Dshot_Cmd, #0
	mov 	Dshot_Cmd_Cnt, #0
	jc	validate_rcp_start

	; Setup timers for Multishot
	mov	IT01CF, #RTX_PIN	; Route RCP input to INT0
	mov	TCON, #11h		; Timer 0 run and INT0 edge triggered
	mov	CKCON0, #04h		; Timer 0 clock is system clock
	mov	TMOD, #09h		; Timer 0 set to 16bits and gated by INT0
	; Setup interrupts for Multishot
	setb	IE_ET0			; Enable timer 0 interrupts
	clr	IE_ET1			; Disable timer 1 interrupts
	clr	IE_EX1			; Disable int1 interrupts
	; Test whether signal is Multishot
	clr	Flags2.RCP_DSHOT
	setb	Flags2.RCP_MULTISHOT			; Set Multishot flag
	mov	Rcp_Outside_Range_Cnt, #0		; Reset out of range counter
	call wait100ms						; Wait for new RC pulse
	clr	C
	mov	A, Rcp_Outside_Range_Cnt			; Check how many pulses were outside normal range ("900-2235us")
	subb	A, #10
	jc	validate_rcp_start

如果都不满足，那么跳回no signal，继续检查。

	ajmp	init_no_signal

要是检测到上述任一个信号，那么再等3 ms, 看看jb    Flags2.RCP_UPDATED，是不是有设置，应该就是说再去读一个输入值了吧。就是没有设置，那么跳回init_no_signal， 继续检查。

validate_rcp_start:
	; Validate RC pulse
	call wait3ms						; Wait for new RC pulse
	jb	Flags2.RCP_UPDATED, ($+6)		; Is there an updated RC pulse available - proceed
	ljmp	init_no_signal					; Go back to detect input signal

信号ok了，那么开始一个长beep  f1了 , 这里没有wait30ms, 其实就是do加长三倍。

; Beep arm sequence start signal
	clr 	IE_EA						; Disable all interrupts
	call beep_f1						; Signal that RC pulse is ready
	call beep_f1
	call beep_f1
	setb	IE_EA						; Enable all interrupts
	call wait200ms	

开启arming序列, 要是dshot协议, 或者是双向打开，那么不会进行油门校准，直接跳到program_by_tx_checked, 如果设置没有打开tx program这里也会跳到program_by_tx_checked。

	; Arming sequence start
arming_start:
	jb	Flags2.RCP_DSHOT, ($+6)	; Disable tx programming for DShot
	jnb	Flags3.PGM_BIDIR, ($+6) ; Disable  tx programming for bidir

	ljmp	program_by_tx_checked	; Disable tx programming if bidirectional operation

	call wait3ms
	mov	Temp1, #Pgm_Enable_TX_Program; Start programming mode entry if enabled
	mov	A, @Temp1				
	clr	C
	subb	A, #1				; Is TX programming enabled?
	jnc 	arming_initial_arm_check	; Yes - proceed

	jmp	program_by_tx_checked	; No - branch

进行arming_initial_arm_check，Initial_Arm（这个变量在开始是1， 在arming完成之后会置0）是不是1, 要是零，也跳到program_by_tx_checked

arming_initial_arm_check:
	mov	A, Initial_Arm			; Yes - check if it is initial arm sequence
	clr	C
	subb	A, #1				; Is it the initial arm sequence?
	jnc 	arming_check			; Yes - proceed

	jmp 	program_by_tx_checked	; No - branch

开始arming_check, 找出补偿，然后等100ms, 看看New_Rcp是不是超过中位（255/2），如果不是的话，那么也跳到program_by_tx_checked。否则等1ms, 然后beep_f4,  上面这个循环两次(throttle_high_cal开始）。

就是说你的油门要是一直在高位，你听到两个f4的beep.

两声beep之后，开计算平均油门。然后等200ms, 开始响成功beep，这个是f1,f2,f3,f4等10ms, 重复三次。  这个代码在inc里。

保存这个油门值在 Pgm_Max_Throttle

arming_check:
	; Initialize flash keys to valid values
	mov	Flash_Key_1, #0A5h
	mov	Flash_Key_2, #0F1h
	; Throttle calibration and tx program entry
	mov	Temp8, #2				; Set 1 seconds wait time
throttle_high_cal:			
	setb	Flags2.RCP_FULL_RANGE	; Set range to 1000-2020us
	call	find_throttle_gains		; Set throttle gains
	call wait100ms				; Wait for new throttle value
	clr	IE_EA				; Disable interrupts (freeze New_Rcp value)
	clr	Flags2.RCP_FULL_RANGE	; Set programmed range
	call	find_throttle_gains		; Set throttle gains
	clr	C
	mov	A, New_Rcp			; Load new RC pulse value
	subb	A, #(255/2)			; Is RC pulse above midstick?
	setb	IE_EA				; Enable interrupts
	jc	program_by_tx_checked	; No - branch

	call wait1ms		
	clr	IE_EA				; Disable all interrupts
	call beep_f4
	setb	IE_EA				; Enable all interrupts
	djnz	Temp8, throttle_high_cal	; Continue to wait

	call	average_throttle
	clr	C
	mov	A, Temp8
	mov	Temp1, #Pgm_Max_Throttle	; Store
	mov	@Temp1, A			
	call wait200ms				
	call	success_beep

然后等用户打遥杆输入低油门， 找出补偿，然后等100ms, 看看New_Rcp是不是低于 中位（255/2），不是的话，在跳回throttle_low_cal循环续等。

等到小于中位的油门，就响beep_f1两次。

比较当前油门(new_Rcp)值是不是 Pgm_Max_Throttle 小 140us（35），如果太小，就是会把Pgm_Max_Throttle设置为当前的最小值+140us(35)，然后等200ms.

 响成功的声音 success_beep_inverted， 这个和高油门的反过来了，就是f4, f3, f2, f1这样响三次，也是在inc文件里，这里为会了不打断主流程也不列贴出来了。

throttle_low_cal_start:
	mov	Temp8, #10			; Set 3 seconds wait time
throttle_low_cal:			
	setb	Flags2.RCP_FULL_RANGE	; Set range to 1000-2020us
	call	find_throttle_gains		; Set throttle gains
	call wait100ms
	clr	IE_EA				; Disable interrupts (freeze New_Rcp value)
	clr	Flags2.RCP_FULL_RANGE	; Set programmed range
	call	find_throttle_gains		; Set throttle gains
	clr	C
	mov	A, New_Rcp			; Load new RC pulse value
	subb	A, #(255/2)			; Below midstick?
	setb	IE_EA				; Enable interrupts
	jnc	throttle_low_cal_start	; No - start over

	call wait1ms		
	clr	IE_EA				; Disable all interrupts
	call beep_f1
	call wait10ms
	call beep_f1
	setb	IE_EA				; Enable all interrupts
	djnz	Temp8, throttle_low_cal	; Continue to wait

	call	average_throttle
	mov	A, Temp8
	add	A, #3				; Add about 1%
	mov	Temp1, #Pgm_Min_Throttle	; Store
	mov	@Temp1, A			
	mov	Temp1, A				; Min throttle in Temp1
	mov	Temp2, #Pgm_Max_Throttle
	mov	A, @Temp2
	clr	C
	subb	A, #35				; Subtract 35 (140us) from max throttle
	jc	program_by_tx_entry_limit
	subb	A, Temp1				; Subtract min from max
	jnc	program_by_tx_entry_store

program_by_tx_entry_limit:
	mov	A, Temp1				; Load min
	add	A, #35				; Make max 140us higher than min
	mov	Temp1, #Pgm_Max_Throttle	; Store new max
	mov	@Temp1, A

program_by_tx_entry_store:
	call wait200ms				
	call erase_and_store_all_in_eeprom	
	call	success_beep_inverted

然后来到tx编程的等待，这里又会跳回去init_no_signal，这里又会走一次上面的设置代码，但是到了校准高位油门时，因为New_Rcp这时是小于255/2的，所以你听到一声长响的beep_f1(do) 后，就直接会跳到了program_by_tx_checked.

program_by_tx_entry_wait:
	call wait100ms
	call	find_throttle_gains		; Set throttle gains
	ljmp	init_no_signal			; Go back

检查油门是不是低于stop, 是的话，arming结束， 开始长响一个三拍的beep_f4（没有wait,所以连起来了）, 保存 Initial_Arm为0.

program_by_tx_checked:
	; Initialize flash keys to invalid values
	mov	Flash_Key_1, #0
	mov	Flash_Key_2, #0
	call wait100ms				; Wait for new throttle value
	clr	C
	mov	A, New_Rcp			; Load new RC pulse value
	subb	A, #1				; Below stop?
	jc	arm_end_beep			; Yes - proceed

	jmp	arming_start			; No - start over

arm_end_beep:
	; Beep arm sequence end signal
	clr 	IE_EA				; Disable all interrupts
	call beep_f4				; Signal that rcpulse is ready
	call beep_f4
	call beep_f4
	setb	IE_EA				; Enable all interrupts
	call wait200ms

	; Clear initial arm variable
	mov	Initial_Arm, #0

检查信号， 这个其实就是看看 Rcp_Timeout_Cnt是不是零，Rcp_Timeout_Cntd在开始赋值1或10，要是超时这个减少1，要是零表示，有一段时间没有收到油门信号变化了，Timer2(t2), 每32ms会去减一下Rcp_Timeout_Cnt直至到零。Pgm_Beacon_Delay会和Power_On_Wait_Cnt_H相减，要是借位，就会开始beep f4, beep一次Power_On_Wait_Cnt_H会减1，就是Power_On_Wait_Cnt_L是255的时候beep一次了。 这个是用来发出声音来寻机用的。很多地方会跳回wait_for_power_on。

	; Armed and waiting for power on
wait_for_power_on:
	clr	A
	mov	Power_On_Wait_Cnt_L, A	; Clear wait counter
	mov	Power_On_Wait_Cnt_H, A	
wait_for_power_on_loop:
	inc	Power_On_Wait_Cnt_L		; Increment low wait counter
	mov	A, Power_On_Wait_Cnt_L
	cpl	A
	jnz	wait_for_power_on_no_beep; Counter wrapping (about 3 sec) , jump if  A nozero, cpl first, actually jmp if A is not 255

	inc	Power_On_Wait_Cnt_H		; Increment high wait counter
	mov	Temp1, #Pgm_Beacon_Delay
	mov	A, @Temp1
	mov	Temp1, #25		; Approximately 1 min
	dec	A
	jz	beep_delay_set

	mov	Temp1, #50		; Approximately 2 min
	dec	A
	jz	beep_delay_set

	mov	Temp1, #125		; Approximately 5 min
	dec	A
	jz	beep_delay_set

	mov	Temp1, #250		; Approximately 10 min
	dec	A
	jz	beep_delay_set

	mov	Power_On_Wait_Cnt_H, #0		; Reset counter for infinite delay

beep_delay_set:
	clr	C
	mov	A, Power_On_Wait_Cnt_H
	subb	A, Temp1				; Check against chosen delay
	jc	wait_for_power_on_no_beep; Has delay elapsed?

	call	switch_power_off		; Switch power off in case braking is set
	call	wait1ms
	dec	Power_On_Wait_Cnt_H		; Decrement high wait counter
	mov	Power_On_Wait_Cnt_L, #0	; Set low wait counter
	mov	Temp1, #Pgm_Beacon_Strength
	mov	Beep_Strength, @Temp1
	clr 	IE_EA				; Disable all interrupts
	call beep_f4				; Signal that there is no signal
	setb	IE_EA				; Enable all interrupts
	mov	Temp1, #Pgm_Beep_Strength
	mov	Beep_Strength, @Temp1
	call wait100ms				; Wait for new RC pulse to be measured

wait_for_power_on_no_beep:
	call wait10ms
	mov	A, Rcp_Timeout_Cntd			; Load RC pulse timeout counter value
	jnz	wait_for_power_on_not_missing	; If it is not zero - proceed

	jmp	init_no_signal				; If pulses missing - go back to detect input signal

如果有信号（Rcp_Timeout_Cntd不是零），同时New_Rcp(油门)不是零跳到 wait_for_power_on_nonzero， 再检查一次Rcp_Timeout_Cntd是不是零，要是不是零，那就跳到init_start

wait_for_power_on_not_missing:
	clr	C
	mov	A, New_Rcp			; Load new RC pulse value
	subb	A, #1		 		; Higher than stop
	jnc	wait_for_power_on_nonzero	; Yes - proceed

	clr	C
	mov	A, Dshot_Cmd
	subb	A, #1		 		; 1 or higher
	jnc	check_dshot_cmd		; Check Dshot command

	ljmp	wait_for_power_on_loop	; If not Dshot command - start over

wait_for_power_on_nonzero:
	lcall wait100ms			; Wait to see if start pulse was only a glitch
	mov	A, Rcp_Timeout_Cntd		; Load RC pulse timeout counter value
	jnz	($+5)				; If it is not zero - proceed
	ljmp	init_no_signal			; If it is zero (pulses missing) - go back to detect input signal

	mov 	Dshot_Cmd, #0
	mov 	Dshot_Cmd_Cnt, #0
	ljmp init_start

上面基本上是准备阶段，下一篇 我们继续读init_start ,  开始驱动电机去工作了。 未完待续！