LaunchBank1_220_v2.pbp

; This patch changes behaviour of the Back button
; in watchfaces:
; When you press twice it from any watchface,
; it will launch app installed in bank 0 (the first bank).
; Note that only double-press is handled;
; double-press is counted as two presses within lesser than 500 ms.
; You may choose which app is installed in bank0
; by uninstalling and reinstalling apps in desired order.
;
; This version works with 2.2.0, any HW version.
#ver 220

; just a simple mask to find named proc
08 4b 10 b5 04 46 18 68 08 e0 {
	proc app_manager_get_bank_info 
}

1f b5 04 46 30 b9 0a 48 {
	proc app_manager_launch 
}

37 B5 0D 46 04 46 0D F1 02 01 01 A8 {
	proc time_ms
}

; This matches some SerialConsole-related proc
; which references memory address used for serial console read buffer.
; We will use this address to store timer value.
08 B5 05 4B 1B 78 13 B9  3E 20 ?4 03 4B
00 22 C3 F8 84 20 08 BD  ?4 @ {
	val counter_ptr
}

; This matches the end of watchface_button_handler proc.
; We replace its POP {R3-R5,LR} with jump.
;
; About mask: '?n' means "skip n bytes"
; (which may have different values in different builds).
; n defaults to 1 if omitted.
; '@' means position to which this mask will resolve
; (defaults to first byte).
; Here we want to match the end of proc
; and replace only its last instruction (with alignment NOP).
; Note that B.W takes 4 bytes, not 2.
00 2c 0c bf 05 20 06 20 BD E8 38 40 ?4 @ 38 BD 00 BF {
	B.W my_code
}

; add our code
{
	proc my_code
	CMP R3, 5 ; as in proc itself
	BEQ ret
	CMP R0,0 ; only match Back button
	BNE ret

	; check if this is first or subsequent btn press
	LDR R0, counter
	LDR R4, [R0] ; get old counter value
	MOV R1, 0
	BL time_ms
	LDR R2, counter
	LDR R1, [R2]
	MOV.W R3, 1000
	MUL R1, R3 ; convert seconds to millis
	ADD R0, R1 ; now R0 contains full timestamp
	STR R0, [R2] ; update counter value
	SUB R0, R0, R4 ; calculate diff
	MOV.W R3, 500 ; delay in millis
	CMP R0, R3
	BHI ret ; if diff is too large, ignore this press

	; now launch app: get its info -
	launch:
	MOV R0,0	; 0 is bank_id
	BL app_manager_get_bank_info
	CBZ R0, ret ; if no such app, just return
	LDR R0, [R0,0xC] ; get app id from bank info
	BL app_manager_launch

	ret:
	db 38 BD ; POP {R3-R5,PC}

	; ---------------------------

	; data block
	ALIGN 4
	counter: ; memory location for click counter. 
	DCD counter_ptr ; this should be a serial console's read buffer
}