I have one of the 5.7" Inky Impression eHats and one of the 1.54" LCD SPI breakout screens. I’d really like to be able to use the pins on the back of the Inky to drive the LCD screen. Most of the pins are easy to map… power and ground are obvious, as are SCK (GPIO 11) and MOSI (GPIO 10). I’m pretty sure that the pin labeled CS on the LCD screen is the same as the pin labeled CE1 on the Inky (both are GPIO 7), and that the pin labeled DC on the LCD is the pin labeled MSO on the Inky (both are GPIO 9).
However, the pin labeled BL on the LCD (GPIO 19) seems to have no mate on the Inky; the remaining pins are GPIO 2, 3, and (I think) 4. GPIO 2 is I2C1 SDA, GPIO 3 is I2C1 SCL, and GPIO 4 is GPCLK0. GPIO 19 is PCM FS.
Does the LCD screen need a pulse modulator? For what does BL stand? Did I get the other pins matched correctly?
Any help is welcome!