MP3@64 stuttering and skipping

[bloodline]

Hmm, I thought there was something in Paula that did it. It's been a long time since I looked at this stuff

Assuming there is no hardware MFM, then even better. One less thing to worry about on the device end. You've got a DMA driven serial port that should be able to shift data at a high enough bitrate for a lot of mp3s...

Without meaning to disparage the old lady (25years isn't old!!!), she was a simple little beast... but that is why she was so flexible... I think the amiga could even read the weird Mac disk encoding schemes, with the right software... Näturlich...

[Karlos]

Theoretically then, what's the show stopper for using the floppy port to send data to a device that expects to recieve serial information?

I always thought the floppy connector was an underutilised expansion port.

[bloodline]

Theoretically then, what's the show stopper for using the floppy port to send data to a device that expects to recieve serial information?

I always thought the floppy connector was an underutilised expansion port.

I used to think the same... but now, it's just non-standard low speed serial port, which probably requires quite a bit of work to interface with... the clockport is simply easier and fast as it sits on the 68k's bus...

[platon42]

Interesting stuff... didnt know there was no DMA to parallel port. Damn that's a bit of an oversight. I am sure there must be a technological reason why not.

Probably because it requires additional logic to conditionally DMA stuff depending on the _ACK handshake signal of the printer connected to the parallel port. I don't think this line (or any other CIA line) is routed back to the DMA engine in the Agnus chip.

[platon42]

Thank you Chris for that good, concise explanation. It seems that there wouldn't be much benefit for me to switch to the MP3@64. Do you know why the interrupt isn't used? Or if it might be possible to modify the MP3@64 or the MAS player to use it? I guess then it would also need a new MHI library...

I am hoping to be able to use the internal serial port with my project, but it can be run at low speed (9.6k should be enough) as it's only used to update an LCD display and maybe receive IR remote codes in the future, so I don't think the interrupt load will be too high. If it is, do you think that could be improved by switching to the MP3@64?

It probably would need some sort of transistor or inverter gate. I haven't looked at the schematics for a long time. The interrupt wasn't used on the MP3@64 as it was specifically designed for the C64 and not for the Amiga.

9600 bits/sec is not a high load for the serial port. 115200 bits/sec surely is (and barely achievable).

[platon42]

Hmm, I thought there was something in Paula that did it. It's been a long time since I looked at this stuff

Assuming there is no hardware MFM, then even better. One less thing to worry about on the device end. You've got a DMA driven serial port that should be able to shift data at a high enough bitrate for a lot of mp3s...

I once wrote a device that would use 2bit -> 3bit encoding but it only worked reliably for the first 40 cylinders. That would have provided >2.5 MB/HD (32 sectors) or >1.2 MB/DD (16 sectors) disk. But I canceled the project because at that time (1998) already the use of floppy disks was dwindling.

The blitter was used to generate the MFM encoding (3 passes for bit splicing and remerging) and decoding (1 pass for merging).

I googled for nearly one hour to find the DMA speed of the floppy controller, but I wasn't successful. The closest estimate I can give is about this one: there are three DMA slots for disk and one slot for each audio channel. While at PAL the maximum replay frequency is about 28 KHz (2 samples per slot), and the disk DMA is supposed to transfer one byte per slot, I get a theoretical maximum speed of about 42 KB/sec for disk DMA.

(As the DMA assignment didn't change even with AGA, this is the reason why Amiga HD drives spin at half speed, because Paula cannot keep up the required data rate.)

[Karlos]

... I get a theoretical maximum speed of about 42 KB/sec for disk DMA.

So, even if the achieveable rate were only half that, that's still >200Kbps. Sounds ample for our theoretical floppy port mp3 decoder

[AmigaNut08]

Hi all,
 Here's the latest after i tried the MP3@64 in my A2000 with the Buddha card.
 
1st i installed all the needed software, then connected the MP3@64 to the Buddha. I then fired up the A2000. I was so excited during bootup that all was going ok, untill i saw a heap of smoke coming from the MP3@64. Man i fried the chip that sits in the middle of the MAS chip and the crystal. I must have had the orientation of the cable f*cked up. I plugged it in with the red line on the ribbon cable running the same way (Left) it did when i plugged it into my A1200. I guess i should have had the red line to the right of the card. At the time i also had the floppy power cable in the Buddha to power a 2.5" HD. That would not have caused the chip to fry would it???

 Ok, this little incident isnt going to put me off from having my Amiga play MP3's in full 16 bit stereo sound as i am going to purchase another card. The question i have now, (i should have asked this 1st as it would have saved me $100) when i receive my new MP3@64, which way does the red line on the cable face on the Buddha. The HD cable has the red line on the ribbon cable facing to the right. Do i follow the same orientation as the HD cable and have the red line on the MP3@64 ribbon cable also facing right?? Also does the Red line on the ribbon stay the same (its to the left of the audio plugs facing away from the card) as it does when plugged in the A1200. or another way to ask so i dont confuse people as i am confusing myself as i write, does the cable that is attached to the MP3@64 stay the same on the card if it is used on an A1200 or a Buddha??


Cheers

[AmigaHeretic]

Are you just loading the MP3 off an IDE HD from the internal IDE port?  Maybe when you get the new MP3@64 try copying the MP3 to the RamDisk: and see if playing out of RAM makes any difference.  

( I remember setting up my first 80meg HD back in '94 on my A1200 and had a hell of time with the Transfer Mask (I think) setting.  Had to change it something like 0xfffffffff....  When the HD was first set up any single file that was over 128k got corrupted, HD was slow, etc..  That is obviously a totally difference simpton, but maybe could be something with the HD transfer??)

I was also unable to get my ethernet adapter to work through the credit card slot as i was told my mobo also needed a mod done because the port would not reset with the given software. I was unable to connect to my router so i ended up selling the ethernet card. Not all A1200's suffer from these above mentioned issues...

I had similar problems with my A1200 and PCMCIA ethernet card back in the day.  There are two programs from Aminet that did the trick for me...

CardPatch.lha
CardReset.lha

As far as I know these basically replaced the need for the hardware patch the PCMCIA needed.

Good luck.

[AmigaHeretic]

So, even if the achieveable rate were only half that, that's still >200Kbps. Sounds ample for our theoretical floppy port mp3 decoder

Why not off the joystick port?  I hear the Amiga joystick ports are fast. ;-)

[bloodline]

Why not off the joystick port?  I hear the Amiga joystick ports are fast. ;-)

:roflmao: :roflmao: :roflmao: :roflmao: :roflmao: +1

[Daedalus]

@AmigaNut08

Ouch! Yeah, the clockport (and its clones) have access to the +5V line which is only restricted by what the traces can carry, so it's very easy to burn things out! Does the Buddha card not have a mark showing which end is pin 1? Even this howevr isn't a good indication... From the Amiga Hardware Database:

- when installed in Zorro slot, pin 40 of the card's clock port is towards the front side of the computer, pin 19 resp. pin 1 towards the rear side

- marked wire of clock port expansions go to pin 19 or pin 40, depending on the manufacturer's definition - e.g. expansions made by Individual Computers are installed with the red stripe on pin 40 (to the left), expansions of E3B mark pin 19 / pin 1 (to the right)

Having the floppy connector plugged in wouldn't have caused this, but it might have prevented damage to the motherboard/Buddha card by not pulling all that power through them - depending on their design of course.

[AmigaNut08]

Hi,
 There is a mark showing pin 1 on the 2 ide connectors on the Buddha card but i dont think there was an indicator showing pin 1 on the clockport connector.
 Well luckily the Buddha card is still ok as i am using it with a HD connected to it.