[sdiy] MIDI too fast?

Paul Cunningham paul at cometway.com
Wed Jun 16 20:25:04 CEST 2010


you could probably double the clock speed, but then the problem is that it would decrease the length of timing loops used for envelopes and lfos. the firmware is not written for any other cpu speed. in the matrix-1000 it's pretty remarkable that the little 1MHz 8-bit 6809 can get so much done in so little time. midi processing is a small part of that and a better workaround would be adding an additional UART with a reasonably sized buffer from a PIC chip. you can't make the matrix-1000 faster, but you can accommodate its weaknesses with double-buffering, data throttling, and midi filtering for filter redundant messages and whatnot.

that's pretty funny that the poly-800 has a buffer overflow vulnerability that overwrites user programs.

does anyone manufacture a UART chip that has its own internal buffer ram? -pc


On Jun 16, 2010, at 1:59 PM, Joel B wrote:

> Hi Peter,
> 
> Any ideas if thus could be done with th 6809 in a matrix 1000? That machine suffers terribly from it's slow CPU.
> 
> On Jun 16, 2010, at 3:35 AM, Ullrich Peter <Peter.Ullrich at kapsch.net> wrote:
> 
>> Hi!
>> 
>>> Wonder if the cpu's on these old synths could be replaced with
>>> something faster that has the same instruction set or over clock the
>>> cpu, without screwing up the functionality... I would imagine it would
>>> depend on how the coding was done, if the programmers used the CPU
>>> speed to calculate timing that would probably mean you are stuck with
>>> that CPU...
>> 
>> Some of the older synth used the 8051 series microncontrollers.
>> Especially these microcontrollers that are still alive have been
>> Upgraded with faster cores and some of them should perform like the
>> original part but faster execution times. So the peripheral parts have to
>> react the same (timers, uarts) but the execution can be optimized.
>> With these new parts a software upgrade that adds some functionality
>> Or improves the standard functionality or timing (f.e. midi latency) would
>> be possible.
>> 
>> Some of the newer parts have different chip housings, so maybe adapter
>> PCBs are necessary.
>> 
>> Some of the improved 8051 series are/were from:
>> Dallas(Maxim), Silicon Labs, Intel (80c251)
>> 
>> But there were also some manufacturers that took the standard core and
>> only made it faster. Years ago I got a sample of a 40MHz 8031 CPU (normally 12MHz).
>> The problem that time was to find an eprom that could deliver the code in the short time...
>> 
>> Nowadays the fast 8051 CPU that go even beyond 100MHz work with integrated
>> flash memory that has been optimized for the speed. So if you want to use such a chip
>> you have the remove or disable the eprom in the synth.
>> 
>> Ciao
>> Peter



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