lowest level for outputting a char to the serial port on ff-xc8.asm for avr

[ronny suy]

Hi ,
I succesfully build and programmed FF5 on an atmega1284P.
I've also build a terminal myself with dvi output and usb keyboard.
Problem is that when the screeen scrolls it takes some time because the scrolling is graphics based , not char based. Therefore I used a 'busy' signal from the picodvi to the atmega1284 on pinb0. I want to test this pinb0 just before or just after the sending of a char. I tried it in the label TX0 , but that doesn't seems to work (tried it on both places where the uart is written to).
Where exactly have I to put my code ?
BTW : the code is tested on another avr board using assembler so I know it's working
Hoping someone can help.
Kind regards,
Ronny

[ronny suy]

Found the solution myself !
I used the EMIT label to add my busy signal check.
I also had to use lds instead of in to read pinb .
Ronny.

[Mikael Nordman]

This where I would have put it.

TX0_LOOP:
        rcall   PAUSE
                  PUT TEST AND LOOP to TX0_LOOP HERE
         sbrs    t0, 5        ; UDRE0, UDRE USART Data Register Empty
        rjmp    TX0_LOOP
        m_out   UDR0_, tosl
        m_drop
        ret

[ronny suy]

I will try it again , I originally used to do this , but discovered my fault with the lds instead of in instruction in the emit routine.

[ronny suy]

Hi Mikael
Tried it in tx0_loop , and it works now :-)
Thanks for your info.