Default SPI frequency? Moderators: adafruit_support_bill, adafruit

[thezim]

Working with a Sparkfun Thing+ RP2040

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spi = busio.SPI(board.SD_SCK, MOSI=board.SD_MOSI, MISO=board.SD_MISO)
print(f"SPI frequency: {spi.frequency}")

This prints:

SPI frequency: 0

So what is the default SPI frequency being used here? Is default SPI frequency define in the board module, if so where.

The following does display the frequency.

Code: Select all | TOGGLE FULL SIZE

spi = busio.SPI(board.SD_SCK, MOSI=board.SD_MOSI, MISO=board.SD_MISO)
spi.try_lock()
spi.configure(baudrate=24000000)
spi.unlock()
print(f"SPI frequency: {spi.frequency}")

SPI frequency: 20833333

[danhalbert]

You have found a bug! The default SPI frequency is 250kHz, but the `busio.SPI()` constructor fails to set an internal variable that remembers the frequency that was set.

Tracking the bug here: https://github.com/adafruit/circuitpython/issues/5836

Thanks for noticing this!

[thezim]

You have found a bug! The default SPI frequency is 250kHz, but the `busio.SPI()` constructor fails to set an internal variable that remembers the frequency that was set.

Tracking the bug here: https://github.com/adafruit/circuitpython/issues/5836

Thanks for noticing this!

For my edification exactly where is 250kHz defined in the code? I had trouble tracking down what repo has this code in it.

Thanks.

[danhalbert]

For my edification exactly where is 250kHz defined in the code? I had trouble tracking down what repo has this code in it.

Here is where it is set:
https://github.com/adafruit/circuitpyth ... /SPI.c#L93

[thezim]

For my edification exactly where is 250kHz defined in the code? I had trouble tracking down what repo has this code in it.

Here is where it is set:
https://github.com/adafruit/circuitpyth ... /SPI.c#L93

Thanks. As an aside is code search busted on GitHub?

https://github.com/adafruit/circuitpyth ... ever_reset

Why does this not find any code an only issues?

[danhalbert]

It does not find code because adafruit/circuitpython is a fork of micropython/micropython, and GitHub doesn't search forks. So we'd recommend cloning the repo and doing local searches for now.

GitHub's new codesearch, https://cs.github.com, does search forks, but it is in limited-invite beta. (I got a beta invitation this morning and just tried searching.)

[rsbohn]

I think this goes beyond just reporting the wrong frequency.

Trying to drive the 1.14" PiTFT on the Pi Zero W. It takes 136 seconds to fill the 135x240 screen with a constant color565 value. This doesn't seem to be running at 64 MHz.

If it reports a faster frequency the screen fill takes less than one second. If `spi.frequency==0` don't even bother loading the display driver. Request a hard reset and hope for a better result next time around.

[tannewt]

@rsbohn, that's a separate issue with the broadcom port. I think you've filed an issue already, so that's the place to discuss it.