Using 320x480 panels with the GD library

There are a lot of 320x480 (HVGA) LCD panels based on the ILI9488 controller. This panel was originally used by smartphones a few years ago, which explains its abundance and unusual "portrait" aspect ratio. For example the ME810A-HV35R module from Bridgetek has an ILI9488 controller, together with an FT810 for running the graphics and touch.

The ILI9488 can run in lots of modes, but requires a short startup sequence to get it into RGB mode. Once in RGB mode the display can be driven by the FT810 with the GD library.

In addition to the usual RGB and SYNC signals, the 320x480 panels also have control signals for communicating with the ILI9488:

CSX	chip select, active low
DCX	data/command select
SCL	clock, rising edge
SDA	data in to ILI9488
SDO	data out from ILI9488
M0	protocol select
M1	protocol select
M2	protocol select

The ILI9488 datasheet calls this "4-line SPI" protocol. To enable it, tie M0, M1 and M2 to VCC.

The Arduino sketch to do the full setup is here:

https://github.com/jamesbowman/gd2-lib/blob/master/contrib/ili9488.ino

The definitions for the signals are at the top of the file - adjust as required for your layout. Here is the hookup list for the ME810A-HV35R module:

arduino pin	name	ME810A-HV35R pin	description
8		2	FT810 select, active low
6	CSX	8	ILI9488 select, active low
5	DCX	7	data/command select
13	SCL	1	clock, rising edge
11	SDA	4	data in to ILI9488
12	SDO	3	data out from ILI9488

Note that the Bridgetek module has extra circuits to allow SDO to share the MISO signal with the FT810, this may not be the case in other designs, so use another pin for SDO if necessary.

A single function gd_ili9488_init() sets up the FT810 and the ILI9488. It also reports the ILI9488 register contents, as confirmation that communication is happening. So you should see:

GD init                               starting FT810 setup
Setting video timing for ILI9488      set FT810 regs for HVGA timing
ID: 7C                                confirms that FT810 is running

ID1: 54                               these are fixed ID regs
ID2: 80
ID3: 66
DISPLAY_IDENTIFICATION: 2A
DISPLAY_POWERMODE: 8                  these are in power-up state
MADCTRL: 0
PIXEL_FORMAT: 6
DISPLAY_SIGNALMODE: 0
                                      (ILI9488 is configured for RGB mode)

ID1: 54                               ID registers are same
ID2: 80
ID3: 66
DISPLAY_IDENTIFICATION: 2A
DISPLAY_POWERMODE: 9C                 regs now configured for RGB mode
MADCTRL: 48
PIXEL_FORMAT: 66
DISPLAY_SIGNALMODE: 38

The sketch just displays "hello world" - you can extend it for your application.