The Sinclair QL Forum

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void setup() {
     pinMode(LED_BUILTIN, OUTPUT);
}

void loop() {
    digitalWrite(LED_BUILTIN, HIGH);
    delay(1000);
    digitalWrite(LED_BUILTIN, LOW);
    delay(1000);
}    

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void setup() {
     DDRB |= (1 << DDB5);
}

void loop() {
    PINB |= (1 << PINB5);
    delay(1000);
}    

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#include "avr/io.h"
#include "util/delay.h"

int main() {
    // SETUP:
    DDRB |= (1 << DDB5);
    
    // LOOP:
    PINB |= (1 << PINB5);
    _delay_ms(1000);
}    

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;=============================================================
; This program flashes the LED on an Arduino board, using the
; Atmel ATmega328 microprocessor. The LED is on Pin 5 of
; Port B, aka PB5 (Arduino D13).
;
; Assemble with:
; gavrasm QuickStart.asm
;
; Upload with:
; avrdude -p m328p -c arduino -P /dev/ttyUSB0 -C \
;          <config_file> -U flash:w:QuickStart.hex
;
; Norman Dunbar
; 01 February 2021
;=============================================================

;-------------------------------------------------------------
; Declare the device, the microcontroller, we are using.
;-------------------------------------------------------------
.DEVICE ATmega328P

;-------------------------------------------------------------
; Tell the assembler we are in the code segment. This is not
; strictly necessary, but it's wise to be explicit.
;-------------------------------------------------------------
.CSEG

;-------------------------------------------------------------
; Tell the assembler to begin at address 0 in the flash. This
; is where the device will start executing on a power up or a
; reset.
;-------------------------------------------------------------
.ORG 0

;-------------------------------------------------------------
; Normally, the interrupt vectors go at address 0 (depending
; on a fuse setting) but as we have no interrupts enabled, we
; can use the vector space for code.

; As we also don't make any subroutine calls, the stack is not
; used. In this case, we don't bother to initialise the stack
; pointer.

; Register Usage:
;
; R16 is a temporary register used to initialise others.
; R17 is the lowest byte of the delay counter.
; R18 is the middle byte of the delay counter.
; R19 is the high byte of the delay counter.
;-------------------------------------------------------------


;-------------------------------------------------------------
; Here we give names to the various registers we are using. It
; is an advisable practice to follow and allows you to change
; registers if necessary without having to scan the whole code
; file/files to find every usage of the register name you need
; to change.
;-------------------------------------------------------------
.DEF bit5reg = R16       ; Holds the value 0b00100000 (bit 5)
.DEF delay_l = R17       ; Delay low, mid and high bytes
.DEF delay_m = R18
.DEF delay_h = R19


;-------------------------------------------------------------
;-------------------------------------------------------------
main:
    ldi bit5reg, (1 << DDB5)    ; 0b00100000 =  PORTB, Pin 5 is OUTPUT.
    out DDRB, bit5reg           ; pin DDRB:5 is set to output
    out PORTB, bit5reg          ; initialize the output line to ’high’

;-------------------------------------------------------------
; With r19 set to an initial value of 240 (0xF0) we get a
; delay around 0.197 each time through the delay loop. We need
; two delay period per waveform remember!
;-------------------------------------------------------------
d_lay:
    ldi r19, 0xF0               ; Gives about half a second or so.

;-------------------------------------------------------------
; The delay loop increments r17 until it overflows. This takes
; 767 cycles in total.
;-------------------------------------------------------------
r17lp:
    inc delay_l                  ; Three byte counter delay
    brne r17lp

;-------------------------------------------------------------
; The delay loop increments r18 until it too overflows. If it
; has not overflowed, we skip back and overflow r17 again, and
; again and again until it does.This takes a total of 117,119
; cycles in total.
;-------------------------------------------------------------
r18lp:
    inc delay_m
    brne r17lp

;-------------------------------------------------------------
; The delay loop increments r19 until it too overflows. If it
; has not overflowed, we skip back and overflow r18/r17 again,
; and again and again until it does.This takes a total of
; 3,153,952 cycles in total.
;-------------------------------------------------------------
r19lp:
    inc delay_h
    brne r17lp

;-------------------------------------------------------------
; The delay loop expires after 3,153,952 cycles. We drop in to
; load PINB:5 with a 1 which will toggle PORTB:5.
;-------------------------------------------------------------
toggle:
    out PINB, bit5reg           ; Toggle the LED on PB5.


;-------------------------------------------------------------
; The pin is high (or low), delay again before we change it to
; low (or high).
;-------------------------------------------------------------
    rjmp d_lay                  ; Back to outer loop

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extern "C" int main();