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SPI_BEGIN_TRANSACTION is slowing down transmissions on SAMD51 #400
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Here is the code I used now to reproduce the issue on an ItsyBitsy M4. Just provide rgb data in splash.h and you will see the difference with the line commented out as described above while PCHCTRL and BAUD are configured identically in both cases:
Actually, I do not understand this behaviour, as the mentioned line should not make a difference. Nevetheless, it does. |
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Arduino board: Grand Central M4 Express
Arduino IDE version (found in Arduino -> About Arduino menu): 1.8.19
List the steps to reproduce the problem below (if possible attach a sketch or
copy the sketch code in too):
This modification will reduce the above mentioned delay between consecutive 8-bit transfers to ~0.8us(!).
As to my understanding of the library's design I think that this behaviour is unintended and, additonally, it is really painful because it makes a huge difference in screen build-up: It's the difference between slow top-to-down build-up and an instant one.
P.S. When I had not yet tracked down things to this point, I started a question here: https://forums.adafruit.com/viewtopic.php?t=194182. Nevertheless, I think this issue is appropriate, here.
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