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by ozcar
Sat Jul 12, 2025 1:58 am
Forum: General discussion
Topic: STM32 noob needs help with STM32H523V project
Replies: 14
Views: 715

Re: STM32 noob needs help with STM32H523V project



I want to make sure I understand this: The directly-invoked ISR fired after roughly 160ns, and the attach-interrupt-invoked ISR fired after 800ns?



Yes, that is about it, the stm32duino-provided ISR (EXTI8_IRQHandler() for the pin I was using) got control after 160ns, and my attachInterrupt ...
by ozcar
Tue Jul 08, 2025 10:03 pm
Forum: General discussion
Topic: STM32 noob needs help with STM32H523V project
Replies: 14
Views: 715

Re: STM32 noob needs help with STM32H523V project

I got to do another test to see what sort of delay you would get going directly into your ISR instead of going via the attachInterrupt callback. To do this all I did was set a GPIO pin high in the stm32duino ISR, and with my attachInterrutp callback still in place, set the same GPIO pin low again ...
by ozcar
Tue Jul 08, 2025 11:01 am
Forum: General discussion
Topic: STM32 noob needs help with STM32H523V project
Replies: 14
Views: 715

Re: STM32 noob needs help with STM32H523V project

From what I have seen on other processors, 500ns would be very "ambitious" using attachInterrupt(). I did a quick test now using that on H503, and the time from the interrupt until the ISR was entered varied a bit depending on the optimisation selected, but I could not even get it down to 1μs. So ...
by ozcar
Mon Jul 07, 2025 10:08 pm
Forum: General discussion
Topic: STM32 noob needs help with STM32H523V project
Replies: 14
Views: 715

Re: STM32 noob needs help with STM32H523V project

The vector comes from an assembly .s module, which of course ends up in flash with your code and everything else. For your processor, it looks like it would be startup_stm32h523xx.s, which on my system is in . ..STMicroelectronics\hardware\stm32\2.10.1\system\Drivers\CMSIS\Device\ST\STM32H5xx\Source ...
by ozcar
Mon Jul 07, 2025 9:36 pm
Forum: General discussion
Topic: Cannot send/receive at CDC with general-purpose terminal
Replies: 4
Views: 293

Re: Cannot send/receive at CDC with general-purpose terminal

What's going on with this forum?

Two days ago I saw an update posted by Kogie, which included the sketch (which, for the record, did not write to Serial in setup(), but did write to Serial twice per second in loop() ). Seeing that I did not have a plausible explanation for what is happening, so I ...
by ozcar
Sun Jul 06, 2025 5:25 am
Forum: General discussion
Topic: Cannot send/receive at CDC with general-purpose terminal
Replies: 4
Views: 293

Re: Cannot send/receive at CDC with general-purpose terminal

Do you write to Serial in your loop(), or perhaps only in setup()?
by ozcar
Wed Jul 02, 2025 8:59 pm
Forum: General discussion
Topic: STM32 noob needs help with STM32H523V project
Replies: 14
Views: 715

Re: STM32 noob needs help with STM32H523V project


...

Also, unrelated to I/O: When running at full speed (250 MHz), is the interrupt overhead for a GPIO-initiated interrupt known? By that, I mean: How much time passes between the time that there's a signal transition on the pin until my interrupt-attached code starts executing? And when my ...
by ozcar
Wed Jun 04, 2025 7:22 pm
Forum: Projects
Topic: USB↔BLUE.PILL→DMA→SPI→WS2812B
Replies: 8
Views: 6929

Re: USB↔BLUE.PILL→DMA→SPI→WS2812B


Why guys? could you please explain this to me? :roll:


Why what?

Why it takes that length of time to send data for 8 LEDs?

Why the code in question runs with interrupts disabled?

How SPI can be used instead?

BTW there are many old threads here where different ways of controlling such LEDs ...
by ozcar
Tue Jun 03, 2025 6:10 am
Forum: Projects
Topic: USB↔BLUE.PILL→DMA→SPI→WS2812B
Replies: 8
Views: 6929

Re: USB↔BLUE.PILL→DMA→SPI→WS2812B


the whole duration for one transmission is ~2us , so there is no problem to use a blocking little piece of code


Where does the 2μs come from?

For 800kHz LEDs the nominal transfer time is 1.25μs. Of course, that is per bit, so for 8 RGB LEDs the Neopixel library would disable interrupts for ...
by ozcar
Mon Jun 02, 2025 7:17 am
Forum: Projects
Topic: USB↔BLUE.PILL→DMA→SPI→WS2812B
Replies: 8
Views: 6929

Re: USB↔BLUE.PILL→DMA→SPI→WS2812B

If you just want to get your LEDs to work, the Adafruit Neopixel library has worked for some people. The timing of the pulses it generates is not very precise, but should be good enough. A potential problem with it, depending on what else you need to do, is that it disables interrupts for the ...

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