Hi
I have been trying to control a small 8-led board with WS2812B’s using some SPI examples. Since i have SPI1 used already for other communication, and SPI6 does not have regular DMA, i chose SPI2 (Daisy pin D20), it was not working for a long time because i supposed that baud prescaler is applied to a 400Mhz but then I kinda brute-forced and it worked with a prescaler 4 so i suspect that SPI1,2,3 is driven from some other PLL. So i hope someone could sched a light to some questions i got:
-
what is the actual SPI frequency before prescaler (and which PLL is used - i tried reading the code but somehow it goes deep into HAL and i have little knowledge about low level clock registers)
-
I have the first LED being off color (seems like green is always at max level), and it is not related to that data signal is 3.3V - i have added LVC1G125 (powered from 5v) and it is still the same, i even tried connecting two led boards in parallel, one with and other without level shifting and they look exactly the same. My theory is that i would need more precise control over SPI frequency so maybe changing the PLL clock or so, because i suspect that LED controller part which is collecting data to shift to next pixel is more tolerant and thus '‘fixes’ the timing problems while the pther part which drives PWM on the LED is not that good with vague timings. Is there any side effects if i change PLL for SPIs 1,2,3? And what is proper approach for this? Direct HAL calls or…? Btw, the SPI1 is in use but as slave (other MCU is talking to it)
-
I would like also to try the other, timer PWM + DMA approach, if i can’t fix SPI, but all the examples i have found are for STM32F series and mainly also involving STM32CubeIDE while i would like to either have an example for STM23H MCU or at least to know the timer frequencies etc in words, not in IDE screenshots, so i could try to port example to Daisy. Did anyone try it and could share anything about it?
Thanks in advance, and have a great day!