STe DMA Sound interrupts

[nanard]

I've made a small sound player for STe https://github.com/miniupnp/AtariST/tree/master/steauply
That's my 1st 68k asm code
It is currently using a looping double-buffer and polling the dma registers $FFFF8909 / FFFF890B / FFFF890D to know when to refill it.

I want to improve by using interrupts to avoid the polling.
I experimented a bit, but it looks like I'm missing something about MFP interrupts on the ST. I guess I should acknowledge the interrupt, but I don't know how.

Code: Select all

   ; MFP interrupt
   pea       dmasoundcomplete   ; vector
   move.w    #15,-(sp)      ; Mono monitor detect / DMA sound complete
   move.w    #13,-(sp)      ; Mfpint
   trap      #14         ; Call XBIOS
   addq.l    #8,sp

   move.w   #15,-(sp)   ; Mono monitor detect / DMA sound complete
   move.w    #27,-(sp)      ; Jenabint
   trap      #14         ; Call XBIOS
   addq.l    #4,sp
...
dmasoundcomplete:
   move.w   #$0F0B,$FFFF8240   ; RED / purple
   rte


From what I see the interupt is called once, but then keyboard input doesn't work anymore.

I also read somewhere that DMA sound also triggers timer A interrupt. Is that when sample buffer is complete or for every sample ? It isn't very clear how both INT are working with DMA sound.
http://atari-ste.anvil-soft.com/html/devdocu4.htm

[Cyprian]

below code is needed when you use TOS compatible MFP interrupts:
Timer A:

Code: Select all

bclr    #5,$FFFFFA0F.w      ; Interrupt In-service A - Timer A done

Mono:

Code: Select all

bclr    #7,$FFFFFA0F.w      ; Interrupt In-service A - Mono done

put it before RTE instruction.

[nanard]

thank you, that is exactly what I need !
From what I see only Mono detect interrupt is triggered.

edit:
Ok, I've seen there are infos in The atari-compendium :
http://www.yardley.cc/atari/compendium/ ... .htm#sound
Xbtimer() is the right way to set Timer A

[Foxie]

Not sure if this is helpful, but you might not need to use DMA sound interrupts at all. In fact in some cases you definitely don't want to use DMA sound interrupts (such as if you want stable rasters or sync-locked code).

Instead, you can poll the playback position in the VBL interrupt. Typically something like 501 samples elapse between VBLs at 50Hz, but by measuring how much the playback position has moved since the last VBL, you can effectively support any frame rate (NTSC / mono systems).

The advantage with using the VBL is that you can be sure there are no interrupts triggering during the active-scan portion of the display - which is usually the most time-critical part of the video cycle.

[FedePede04]

below code is needed when you use TOS compatible MFP interrupts:
Timer A:

Code: Select all

bclr    #5,$FFFFFA0F.w      ; Interrupt In-service A - Timer A done

Mono:

Code: Select all

bclr    #7,$FFFFFA0F.w      ; Interrupt In-service A - Mono done

put it before RTE instruction.

hi friend could you please explain what the "Mono done" means.. does it trigger an interrupt?

[FedePede04]

below code is needed when you use TOS compatible MFP interrupts:
Timer A:

Code: Select all

bclr    #5,$FFFFFA0F.w      ; Interrupt In-service A - Timer A done

Mono:

Code: Select all

bclr    #7,$FFFFFA0F.w      ; Interrupt In-service A - Mono done

put it before RTE instruction.

hi friend could you please explain what the "Mono done" means.. does it trigger an interrupt?

ok that was hard, i have been breaking for the last hour
this was exactly what i need, so many thx, i owe you one