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MIDI Interface

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#226 ivop OFFLINE  



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Posted Thu Jan 18, 2018 5:17 AM

Due to having a lot of things outside of working on Atari stuff at the moment, things have slowed down a bit, but I am committed to do at least one run this year. I am currently completely overhauling my enclosure design, similar to what I did to my snes2joy housing. It's a lot more sturdy now. I used to be able to bend the sides inwards, but that's solved now. Especially for an enclosure more than twice the size of the snes2joy, that's very important to me. As for the cost, depending on the interest, PCB+parts will probably around €15,=. Enclosure, SIO cable, Dream Blaster Board, assembly by me, will add to the cost. As for postage and packaging, if it stays under 350g I can send it for €10,= worldwide. With an enclosure, the dimensions will exceed that postal option and I have to move to a full blown package, which will be around €15,= for Europe and €25,= for most of the rest of the world.


Also, I'll probably do a run of snes2joy first, to test managing a larger project than I have ever done before, hobbywise. So, first there's Chinese New Year and Atari Invasion 2k18 which I have to prepare for. After that, I'll start a pre-order thread.

#227 Level42 OFFLINE  



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Posted Thu Jan 18, 2018 11:08 AM

Hope you have a demo model working at Atari Invasion ?

#228 ivop OFFLINE  



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Posted Thu Jan 18, 2018 11:19 AM

Hope you have a demo model working at Atari Invasion ?


Yes, that's the planning. Hopefully with a finished enclosure :) But if by change that won't happen, I will certainly bring a working prototype!

Edited by ivop, Thu Jan 18, 2018 11:20 AM.

#229 mytekcontrols OFFLINE  


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Posted Thu Jan 18, 2018 11:42 AM

Wish I could be there  :(

#230 Spaced Cowboy OFFLINE  

Spaced Cowboy

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Posted Thu Jan 18, 2018 11:57 AM

Just a thought, but what's the processing overhead for playing midi sound ?


I was wondering whether putting a cheap microcontroller on-board would be worth it ? The idea being that you could then reduce it to a command-based interface over SIO:


 - load midi data into the micro's RAM

 - start playing from location X in RAM, optionally looping after Y bytes of data

 - stop playing


You could even introduce a 'command buffer', so you send the midi data, then you send a series of commands - it's like ANTIC for audio with an 'Audio List' rather than a 'Display List'. Each command could then be something like:


 - move to position X in midi data

 - play Y bytes/notes

 - stop playing

 - jump to position X in command-data (to allow infinite loops)


 (if you want to get really fancy, you could introduce loops and variables, but maybe that's pushing it). 


Combine the command approach with the command-buffer and you have the ability to easily switch (stop playing, start processing buffer at $XXXX) between a whole bunch of MIDI tunes without putting essentially any load on the CPU. Ideal for games.


To put this into perspective, an STM32F4 in a 64-pin LQFP (so not too hard to solder) with 256k of Flash (program space) and 128K of RAM (midi data space) is $6.58 in quantity-1.  It has 5v-tolerant pins so it's easy to interface to an A8.


You could easily keep the current mode of operation as well - the STM has 3 USARTs so it can easily be switched into a transparent mode where any data incoming on port A can be output on port B and vice versa. Or you could set it up to buffer incoming data so the A8 could read it without any danger of dropping bytes.



IMHO, offloading the sound would really benefit the machine, and it fits in with the ethos of the original machine too - like I say, it's basically ANTIC for audio.

Edited by Spaced Cowboy, Thu Jan 18, 2018 11:59 AM.

#231 ivop OFFLINE  



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Posted Thu Jan 18, 2018 12:27 PM

@Spaced Cowboy, that's indeed a good idea and something similar was already proposed by Irgendwer, earlier in this thread. To not further complicate this board, it was more or less decided to move such functionality to a future expansion board, which can be attached to the Wave Blaster port.


Wish I could be there  :(


That would have been nice, especially if you could bring a 1088XEL to demo ;)

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