In my application the m5paper goes to deep sleep and should wake after 5 minutes. Sometimes it appears to hang at startup and I also get a series of these messages:

[W][Panel_IT8951.cpp:258] _wait_busy(): [Panel_IT8951] wait_busy: timeout

As @felmu suggested it can be a pullup issue.

In M5GFX.cpp the busy pin is configured with:

lgfx::pinMode(GPIO_NUM_27, lgfx::pin_mode_t::input_pullup); // M5Paper EPD busy pin

However in Panel_IT8951.cpp (Panel_IT8951::init(bool use_reset)) the busy pin is configured with

pinMode(_cfg.pin_busy, pin_mode_t::input);

So it looks like the pin is incorrectly reconfigured and the required pullup is missing.

Now how can I override this behaviour in my application without having to modify the M5GFX.cpp file?

(I am using the Arduino IDE with M5GFX 0.2.17 and M5Unified 0.2.11.)

regards,

Willem-Jan

FWIW: in M5PaperS3 the eInk display is directly controlled by ESP32S3.

In M5Paper the GPIO WaitBusy() checks is GPIO27 which comes directly from IT8951 so I guess if the line never goes HIGH either IT8951 is not (properly) powered or defective.

Anyhow, have you tried to change the code to ignore the busy state of IT8951; maybe add some small delay instead.

BTW: I measured GPIO27 and when M5Paper is running it's being pulled up. I don't see a pull-up resistor in the schematics so I guess IT8951 is pulling it up (when not busy).

Thanks
Felix