Fix BusDisplay transaction handling #10571
Open
+39
−26
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
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); | ||
| } |
There was a problem hiding this comment.
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.
There was a problem hiding this comment.
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.
There was a problem hiding this comment.
That sounds like a good plan. Thanks!
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
2 participants
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
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.