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flaneth
firmware
ser115200_asm.S
BBM play: add serial MCUF output 115200 8N1
Stefan Schuermans
commited
2dde65d
at 2012-05-06 20:04:32
ser115200_asm.S
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; flaneth - flash and ethernet ; Copyright (C) 2007-2012 Stefan Schuermans <stefan@schuermans.info> ; Copyleft: GNU public license V2 - http://www.gnu.org/copyleft/gpl.html ; a BlinkenArea project - http://www.blinkenarea.org/ */ #include <avr/io.h> .section .text ; output = PD3 ; output a byte item with 115200 baud in 8N1 protocol ; extern void Ser115200Out(unsigned char val); .global Ser115200Out .func Ser115200Out Ser115200Out: push R17 push R16 ; parameters: R24=val in R17,SREG-0x20 ; interrupts off cli clt ; start bit in R16,PORTD-0x20 bld R16,3 out PORTD-0x20,R16 rcall wait135 bst R24,0 ; bit 0 in R16,PORTD-0x20 bld R16,3 out PORTD-0x20,R16 rcall wait135 bst R24,1 ; bit 1 in R16,PORTD-0x20 bld R16,3 out PORTD-0x20,R16 rcall wait135 bst R24,2 ; bit 2 in R16,PORTD-0x20 bld R16,3 out PORTD-0x20,R16 rcall wait135 bst R24,3 ; bit 3 in R16,PORTD-0x20 bld R16,3 out PORTD-0x20,R16 rcall wait135 bst R24,4 ; bit 4 in R16,PORTD-0x20 bld R16,3 out PORTD-0x20,R16 rcall wait135 bst R24,5 ; bit 5 in R16,PORTD-0x20 bld R16,3 out PORTD-0x20,R16 rcall wait135 bst R24,6 ; bit 6 in R16,PORTD-0x20 bld R16,3 out PORTD-0x20,R16 rcall wait135 bst R24,7 ; bit 7 in R16,PORTD-0x20 bld R16,3 out PORTD-0x20,R16 rcall wait135 set ; stop bit in R16,PORTD-0x20 bld R16,3 out PORTD-0x20,R16 rcall wait135 out SREG-0x20,R17 ; restore interrupt state pop R16 pop R17 ret .endfunc ; wait 135 cycles (including rcall and ret) wait135: nop ; 2 cycles nop ldi R16, 42 ; 1 cycle, N := 42 wait_loop: dec R16 ; N cycles brne wait_loop ; 2N-1 cycles ret ; 7 cycles (including rcall)
