drivers/lcd: add CMD sequence feature

[gschorcht]

Contribution description

The PR provides the capability to execute a sequence of LCD controller commands defined in a byte array as CLP tuples (command, length, parameter). This can be used for example

• to send an initialization sequence to a controller that is not supported by a controller-specific driver or
• to write specific configuration parameters that are not covered by the controller-specific driver.

The PR introduces the pseudomodule lcd_init_sequence to use the initialization command sequence defined in the driver parameter set instead of the the controller-specific initialization function.

The format of a CLP tuple is:

• one byte the command index
• one byte the length of the following parameters, i.e. the number of bytes representing the parameters for the command. If the command has no parameters, the length is 0.
• n bytes the parameters of the command.

For testing, tests/drivers/st77xx has been extended to use initialize the LCD controller by a intialization command sequence if module lcd_init_sequence is enabled.

Testing procedure

tests/drivers/st77xx should work with enabled lcd_init_sequence:

USEMODULE=lcd_init_sequence BOARD=adafruit-pybadge make -C tests/drivers/st77xx flash

USEMODULE=lcd_init_sequence BOARD=esp32s3-usb-otg make -j8 -C tests/drivers/st77xx flash

Issues/PRs references

[riot-ci]

Murdock results

✔️ PASSED

02feadd fixup! drivers/lcd: add lcd_write_cmd_sequence function

Success	Failures	Total	Runtime
10248	0	10249	17m:14s

Artifacts

• Documentation preview

[benpicco]

I think those should live in the driver, not copy & pasted between applications/boards.
Or is there anything application specific about this?

(Sure it makes sense being able to supply an out-of-tree command sequence, but if we already have some known good init sequences for some boards, they should be easily usable)

[gschorcht]

These init sequences are actually only intended for test and demonstration purposes. They have the disadvantage that they use the parameter macros directly and cannot be parameterized by the parameter set of the device. Furthermore, most of the commands in these example sequences only configure the default values after resetting the display anyway and are actually not needed at all. Last, the default init sequences are already implemented by the driver for the ST77xx variants.

[gschorcht]

I had to rebase the PR to resolve conflicts.

[gschorcht]

I had to rebase the PR.

[Enoch247]

When would using a CMD seq be the preferred method vs adding or extending the LCD specific drivers?

[gschorcht]

After taking a year off, I am slowly trying to resume my work on RIOT-OS and am simply rebasing my old PRs to start with.

[gschorcht]

When would using a CMD seq be the preferred method vs adding or extending the LCD specific drivers?

Sometimes you will only find the sequence of bytes that represent the command sequence for initialization in data sheets, manufacturer examples or reference implementations.In this case, such a function is helpful.

[Enoch247]

When would using a CMD seq be the preferred method vs adding or extending the LCD specific drivers?

Sometimes you will only find the sequence of bytes that represent the command sequence for initialization in data sheets, manufacturer examples or reference implementations.In this case, such a function is helpful.

[Enoch247]

Sorry, I didn't mean to close this. I pressed the wrong button. Re-opening.

[Enoch247]

The part I am unclear on is; what functionality does this PR provide that is not already possible with the existing code. It appears to be a another way to do what is already possible.

If it does not provide new functionality, than an explanation of why the duplicate method is desirable to add would be helpful.

[gschorcht]

The part I am unclear on is; what functionality does this PR provide that is not already possible with the existing code. It appears to be a another way to do what is already possible.

If it does not provide new functionality, than an explanation of why the duplicate method is desirable to add would be helpful.

Instead of using an endless sequence of calls to lcd_ll_write_cmd when you need a specific command sequence, you can simply define the command sequence as a byte array, for example if you have to override the initialization sequence of the controller specific initialization for your display.

It corresponds to the approach as it is done in the Adafriut ST7735 Library: https://github.com/adafruit/Adafruit-ST7735-Library/blob/master/Adafruit_ST7735.cpp#L44-L209