Are other PICs possible?

[SeverityOne]

On one particular mailing list, The Ultimate Sequencer is a regularly recurring subject. I believe that a core module, some buttons, encoders, wheels and a sizeable LCD would make an ideal hardware platform for this - if it weren't for the fact that the PIC18F452 has only 1.5 Kb of RAM.

Since you can plug a PIC16F877 into the core module as well, is this perhaps possible with other PIC types too? In other words, are other (most? all?) 40 pin DIL packages pin compatible?

I've tried to find this information on Microchip's web site, but so far with little success.

Mass storage and different firmware are other issues, but those should be relatively easy to get around.

Thanks,

- Peter

[stryd_one]

I'm already way on top of this ... But it's gonna take ages, so be patient :) I'm sad to say, that it's not nearly as simple as you appear to think.

Using a PIC other than the 18 would just be using a less powerful chip, so that doesn't help at all - we already need more processing power than one PIC18 can provide (the current project with the seq is communications between 2 or more cores). A set of 512k banksticks will be used for RAM, and that's probably enough to hold at least one tune (4M).

4 others from this board (including TK, of course!) and myself have been working on the new firmware, and concepts for it, for about a year now.... Relatively easy? I think not!  ;D

But it'll take more than that to stop us!

[SeverityOne]

Yes, I already figured out that other PICs may have more Flash, but it's practically impossible to find a microcontroller - any microcontroller - with more than a 2 Kb or so of RAM.

I'll take your word for the software: I used to do this sort of thing, long ago, but I'm into distributed enterprise applications now. That runs on different machines, too, but the real-time aspect is a different kettle of fish altogether.

But Banksticks use an EEPROM, right? Can they be written as often as RAM? Because I think a good chunk of RAM is a prerequisite for many applications - although 4 Mb is probably way more than enough for a MIDI sequencer. The things people used to do with an 1Mb Amiga - and that included the samples and a multitasking OS as well.

One last thing. Port J11, does it use a certain protocol? Or is it just data going in and out at a predefined rate? I'm asking because I'm wondering if it'd be feasible to use something other than a PIC (say, a ColdFire) whilst retaining compatibility with the existing modules. I know, yet another code base is not something anyone is looking for; just see it as curiosity from my side.

- Peter