Fix BusDisplay transaction handling #10571
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tannewt requested changes Aug 18, 2025
Comment on lines -166 to 177
| self->send(self->bus, data_type, chip_select, data, data_length); | ||
| displayio_display_bus_end_transaction(self); | ||
| | ||
| if (self->set_current_column_command != NO_COMMAND) { | ||
| uint8_t command = self->set_current_column_command; | ||
| displayio_display_bus_begin_transaction(self); | ||
| self->send(self->bus, DISPLAY_COMMAND, chip_select, &command, 1); | ||
| // Only send the first half of data because it is the first coordinate. | ||
| self->send(self->bus, DISPLAY_DATA, chip_select, data, data_length / 2); | ||
| displayio_display_bus_end_transaction(self); | ||
| } |
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I'm worried all of these deletes are going to break something due to changing chip select issues. I wonder if we should split out the bus locking from chip select.
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Makes sense, I was unaware that some display drivers are fussy about when chip selects are toggled. I can change it back into individual bus transactions for now, and spin in any cmd sequences. This would eliminate the possibility of regressions.
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That sounds like a good plan. Thanks!
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Fixes #10569
I've tested on a m5stack_cores3 with no apparent regressions on display handling. This strangely does not resolve #10536 so some other issue must also be present, however I can see on an oscilloscope that the SPI bus is now being shared correctly between busdisplay and sdcardio. One thing to note is running spi = board.SPI(); spi.try_lock() will now prevent the screen from being updated until the lock is released - this is a limitation of the the hardware.
I have also applied the same/similar fixes to EPaperDisplay - however I do not have hardware to verify this.