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ArmDeveloperEcosystem / st7789-library-for-pico

Use an ST7789 based TFT LCD display with your Raspberry Pi Pico or any RP2040 based board 📺
Apache License 2.0
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Execution hangs on `sleep_us(1)` on Pico W #5

Open cshaa opened 5 months ago

cshaa commented 5 months ago

On my Raspberry Pi Pico W using the latest SDK, trying to use the library leads to crashing the CPU – execution just hangs, and the chip doesn't do anything else. Here's my project that reproduces the bug: pico-st7789-bug. (This is happening regardless of whether there's any display connected to the Pico.)

I found out that it's caused by the sleep_us(1) calls at various places in the code (lines: 28, 33, 38, 40, 45, 50, 159, 164, 170, 175). It seems that there is a race condition in the SDK that leads to missing the interrupt for the short timer and hanging indefinitely – potentially only on Pico W devices. Related issues: https://github.com/raspberrypi/pico-sdk/issues/1552, https://github.com/raspberrypi/pico-sdk/issues/1500, https://github.com/micropython/micropython/issues/12873

If I remove all these sleep_us calls, the library starts working as expected, and I'm able to run the blink example on a 240x240 display. If there isn't sufficient rationale for the sleep_us(1) calls, I advise to remove them altogether – at least for me the library works perfectly without them. However, if they are necessary for correct timing, we can replace them with something like busy_wait_at_least_cycles, and if they're a walkaround for spi_write_blocking not blocking enough, they can be replaced with a busywait until SPI is done:

while (((spi_hw_t *)st7789_cfg.spi)->sr & SPI_SSPSR_BSY_BITS)
{
  tight_loop_contents();
}

I can make a PR with any of the proposed solutions.

TheCustomFHD commented 5 months ago

I will cross-test this with my screen aswell during the weekend, would be interesting if this works for me too.

TheCustomFHD commented 4 months ago

Soo.. it wasnt exactly uh.. "that weekend", sorry for that. BUT! i can confirm, that with a sleep_us(10), my display functions. It also functions without the sleep_us(1)or sleep_us(10) waits. This is very nice for me, and huge thanks to @m93a for figuring this out. Now my old Rapsberry Pi 1 A Screens have a new nice usecase as a screen for my Pico's, amazing!

stale[bot] commented 2 months ago

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

cshaa commented 1 month ago

@stale As far as I know, this is still an issue.

TheCustomFHD commented 1 month ago

I can confirm, this is still broken. Waiting for a response from what the Repository Owner wants to do