I read somewhere that the default backlight control pin is IO02 but thats not right. Someone else said that IO02 is either not supported in Openhasp or that it does not support PWM. OpenHasp is easily configurable and I read in the ESP32 spec sheets that “All pins that can act as outputs can be used as PWM pins”. I also looked at the schematic and see IO02 is R2 on the LCD…
All the IO pins on the ESP are accounted for in their docs except Pins IO35-37 which are not listed but probably just for the PSRam.
It looks like the backlight control pin is actually connected to EXIO02. Which is a CH422G IO expander chip. That would make sense as the expander is an I2C chip that is not capable of PWM. There is a section in ESPHome docs about controlling this chip as it is on several Waveshare boards…..
Maybe I’m just lazy or I really wanted to dim the display at night but I found a youtube video that shows how to connect IO06 to the BL control That works great. Just add a wire from the AD connector(IO06) to pin 4 of the BL chip.
I took a close look and saw a test pad near the ESP chip tha runs over to pin 4 through a zero ohm chip resistor that is really easy to solder to. Right above that chip is a blank spot then a 4.7k pullup. Only drawback is now I cant use IO06 to monitor the batery voltage by connecting it to tp1.
A quick fix and moving on…..
