[sdiy] STM32 processor

[Colin f]

> Just saw that ST have new part (F2) calming 120dmips! Plenty 
> of memory 1M Flash, 256k Ram, should open for serious effects 
> development i suppose.
> 
> I guess Collin F uses a STM for his new sequencer.

He does indeed.
They are awesome.
I'm using the 72MHz part, with external memory bus, but it is basically the
same core.

The dual 12-bit DACs make it especially useful for controlling analogue
devices.
Even more useful, on some of the larger footprint parts, there is external
triggering of the DACs, with DMA update of the values.
For de-muxing many CV outputs, you can use a timer to generate the clock for
an external counter and de-mux circuit.
The same timer also triggers the DAC.
You set up an area in memory to hold the values for each de-mux output, and
configure the DMA controller to cycle through the DAC values on each
trigger.
The de-muxing then happens with no CPU involvement.
You just write a value to the memory location for one of the outputs - next
time round the refresh cycle, the value changes.
Not having any interrupt service for this means you can run the de-mux
refresh at a much higher rate.
DMA is also available for the ADC inputs.
I have this set up for scanning the knobs.
Once configured, the code need only look in the memory location for each
knob, and the current value is always there, written by the DMA.

After years of using many different 8 bit CPUs, the orders of magnitude
performance improvement in switching to this sort of device is well worth
the slight extra effort learning to solder the teensy wee pins.

Cheers,
Colin f