I am trying to learn Arduino programming in assembler, using as an Arduino UNO R3 board and based on the examples of this tutorial: link
I have managed to assemble and record the blink of the first example, which lights an LED connected to pin 13 of the board.
But I would be interested in being able to change the output pin, so instead of using pin 13, use another pin, such as 3.
How could that change?
Finally I found it, in these two lines
ldi r16,0x20 ; set port bits to output mode
out DDRB,r16
The first line says the pin to be used, which is defined by setting its position to 1. Position 5 would be 100000, which in hexadecimal is 20, hence the first instruction. If I wanted to put position 3 I would put 1000, 8 in hexadecimal.
And the port is defined with the DDR *, putting DDRB, DDRD, or the corresponding one.
Finally, the correspondence between the pins of the board and those of the microcontroller is here: link
So, with those two data, I've already been able to define the pins I want to use