The picture was "borrowed" from What have you done to make generic TFT touchscreen display work?
I'm trying to write a driver to use the module from a Pico. I have a preliminary spec I found online for the display chip, but am seeing some things that have yet to make sense to me. For one thing when I walk a "1" down the 16-bit color value the high-order byte seems to be ignored and the lower byte exhibits a RGB behavior in a 3-2-3 bit layout. I can make this work, but this limits the color availability to 256. This format is not documented in the spec I have. The spec outlines a 5-6-5 bit layout for 16-bit color. I then proceeded to attempt 18-bit color, but with this I get 6 bits red, nothing for green, and blue actually appears as cyan (mix of the green and blue).
The board seems to be driving the parallel inputs of the controller chip and doing the serial to parallel conversion using the four ICs shown at the bottom of the board in the picture instead of sending the SPI input directly to the chip. Since the board doesn't seem to allow reading information from the main chip, it is difficult to tell if the high-order bits are even sent to the chip (only the lower byte is used by any of the instructions except 'Memory Write' and 'Memory Write Continue'). The controller chip is sandwiched between the lcd display and the board you can see in the picture. I kind of doubt I would be able to observe anything useful if I pulled the module apart since the ili9486 is packaged in a 1776-ball grid array.
A schematic of the board and/or a newer version of the ili9486 spec would be helpful, if anyone can provide me with one.
