[Cryptech Tech] stm32 <- UART -> cryptech_muxd

[Peter Stuge]

Hi Paul,

Paul Selkirk wrote:
> I fixed this (to the extent I've been able to test it) before I went on
> vacation, but (as Rob deduced) I forgot to push it until today. :P

Oh cool!


> The basic problem is the amount of processing that takes place in the
> interrupt handler (whether it's a direct UART receive interrupt or a DMA
> half/complete interrupt). Under heavy loads, we tended to miss
> characters, mis-order characters, or stutter characters.

Ack, after my quick look I figured that might be the problem - you
obviously have a much more detailed view.


> So I revived the essence of commit 2b6b9f, where I've got a larger DMA
> buffer than I think I'll need, and a once-every-ms task that pulls data
> off, processes it, and queues RPC requests. It tests out well, and the
> UART receive queue doesn't exceed 94 characters, which is consistent
> with a transmission rate of 921600 baud, modulo a bit of jitter in the
> SysTick interrupt.

That's great!


> I don't mind working with CMSIS/HAL, because it's a useful API, and I
> don't think it's necessarily the gating factor in my design. Rather, I
> think it was all the extra work I was trying to do in the interrupt handler.

Nod. CMSIS does add some cost, I was suggesting dropping it primarily
to lose that, but if it works anyway and you like the API then
there's absolutely no reason to change anything.


> I have great hope that this will be more stable, and I can go on to
> spend my time on more interesting/useful work.

Good stuff.

I forget, do you have a USB daughterboard? Ie. could you easily stress
test with the combination of the new stm32 code and the daughterboard?

If not, what has been your stress test so far? Maybe I can replicate it?


Thanks

//Peter