What's the fastest periodic IRQ that you have ever run?We have one board with 12 isolated LPC1758 ARMs. Each gets interruptedby its on-chip ADC at 100 KHz and does a bunch of filtering and runs aPID loop, which outputs to the on-chip DAC. We cranked the CPU clockdown some to save power, so the ISR runs for about 7 usec max.I ask because if I use a Pi Pico on some new projects, it has adual-core 133 MHz CPU, and one core may have enough compute power thatwe wouldn't need an FPGA in a lot of cases. Might even do DDS insoftware.RP2040 floating point is tempting but probably too slow for controluse. Things seem to take 50 or maybe 100 us. Back to scaled integers,I guess.I was also thinking that we could make a 2 or 3-bit DAC with a fewresistors. The IRQ could load that at various places and a scope wouldtrace execution. That would look cool. On the 1758 thing we broughtout a single bit to a test point and raised that during the ISR so wecould see ISR execution time on a scope. My c guy didn't believe thata useful ISR could run at 100K and had no idea what execution timemight be.

On a sunny day (Fri, 13 Jan 2023 15:46:16 -0800) it happened John Larkin wrote in Well in that sort of thing you need to think in asm, instruction times,but I have no experience with the RP2040, and little with ASM on ARM.Should be simple to test how long the C code takes, do you have an RP2040?Playing with one would be a good starting point.Should I get one? Was thinking just for fun...

highest frequency periodic interrupt?

Jan 13, 2023 Last reply: 3 years ago 89 Replies

Rate this thread:

Lasse Langwadt Christensen 3 years ago

torsdag den 19. januar 2023 kl. 13.06.58 UTC+1 skrev John Larkin:

they are basically doing the same as Espressif have been doing for years with:

formatting link

Vote

Join the Discussion

Have something to add? Share your thoughts — no account required.

Didn't find your answer?

Ask the community — no account required