d0vr
Posts: 26
Joined: Sun Oct 28, 2012 11:25 am

.dtb file for ili9325 supporting 8-bit parallel bus?

Sun Mar 18, 2018 3:44 am

I think this is the right section. I'm trying to connect a 240x320 TFT LCD module to my pi. I think it's mainly designed for Arduino, but i was hoping to get it working on pi..

I have found notro's fbtft repo which in theory had support for the ili9325 IC my module uses: https://github.com/notro/fbtft/blob/master/fb_ili9325.c

However, the repo is apparently now out of date and I need a .dtb file. Does anyone know if one already exists - specifically for the 8-bit parallel interface? There is SPI options around, but my board doesn't seem to break those pins out.

Otherwise, is it possible to convert the above C file into the needed .dtb file?

PhilE
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 2523
Joined: Mon Sep 29, 2014 1:07 pm
Location: Cambridge

Re: .dtb file for ili9325 supporting 8-bit parallel bus?

Sun Mar 18, 2018 6:56 pm

The standard "hy28b" overlay uses the ili9325. The documentation for it says:

Code: Select all

Name:   hy28b

Info:   HY28B - 2.8" TFT LCD Display Module by HAOYU Electronics
        Default values match Texy's display shield

Usage:  dtoverlay=hy28b,<param>=<val>

Params: speed                   Display SPI bus speed

        rotate                  Display rotation {0,90,180,270}

        fps                     Delay between frame updates

        debug                   Debug output level {0-7}

        xohms                   Touchpanel sensitivity (X-plate resistance)

        resetgpio               GPIO used to reset controller

        ledgpio                 GPIO used to control backlight

notro
Posts: 695
Joined: Tue Oct 16, 2012 6:21 pm
Location: Drammen, Norway

Re: .dtb file for ili9325 supporting 8-bit parallel bus?

Sun Mar 18, 2018 7:41 pm

I couldn't find a known working example, but a Device Tree overlay would look something like this:

Code: Select all

/dts-v1/;
/plugin/;

/ {
	compatible = "brcm,bcm2835";

	[email protected] {
		target-path = "/soc";
		__overlay__ {
			/* needed to avoid dtc warning */
			#address-cells = <1>;
			#size-cells = <0>;

			[email protected]{
				compatible = "ilitek,ili9325";
				buswidth = <8>;

				reset-gpios = = <&gpio n 0>;
				dc-gpios = <&gpio n 0>;
				wr-gpios = <&gpio n 0>;
				db-gpios = <&gpio n 0>, /* db0 */
					   <&gpio n 0>, /* db1 */
					   <&gpio n 0>, /* db2 */
					   <&gpio n 0>, /* db3 */
					   <&gpio n 0>, /* db4 */
					   <&gpio n 0>, /* db5 */
					   <&gpio n 0>, /* db6 */
					   <&gpio n 0>; /* db7 */
				led-gpios = <&gpio n 0>;

				debug = <7>;
			};

		};
	};
};
reset,dc and led-gpios are optional from the driver point of view. debug=7 gives a lot of info in the kernel log to help debug any issues.

Be aware that this will be a lot slower than using the SPI bus. gpio bitbanging is slow. SPI has the added benefit of using dma.

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