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0 pointstaneq3y ago0 comments

The ESP32 is stronk. I wasted a bunch of time implementing fixed point maths and lookup table trig functions because “of course” before testing it and finding that for our purposes just calling sin/cos wasn’t an issue.

Edit: If you’re doing ‘real’ real-time stuff then make sure you get a dual core model and use core 2 for time sensitive things, though. The wifi stack uses up some solid chunks of time.

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pjmlp3y ago

To be fair, back in the day most likely you have had to use fixed point math. :)

taneqOP3y ago

Yep, I think the last proper embedded project I worked on before this one was on an i386EX running at 40MHz, trying to eke 40KHz sample rate processing the output of a line scan CCD. I, a brash 22yo, declared it impossible to process ~250 pixels in 10 clock cycles (there was DMA and cool dual-port RAM stuff going on). My boss at the time explained the obvious way to approach it and I tried again, I think I got to 36KHz or something after pulling out all the stops. Fun times.

The idea that you could just use trig functions and get away with it on a micro is still kinda foreign. :P

HeyLaughingBoy3y ago

The problem is that today, a lot of programmers remember that and ignore the fact that you can often do floating point math on a modern real time system and meet all your deadlines.

Just last week I fixed a bug in such a system: in an effort to speed things up by avoiding floating point math, calculations were done with uint32_t's and the developer(s) didn't notice that in some cases there was an internal overflow before the final result was produced.

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