# Use 2.8 inch TFT displays on SPI ports

<abstract>
This article explains how to wire and manage up two 2.8" inch graphic display 240x320 wired on the SPI ports of a RoadRunner SOM. 
</abstract>

Unfortunately on SAMD2 architecture is not available the driver to manage the resistive touch
available on XTERM-01

* Kernel used: [4.19.78](/roadrunner_compile_kernel_4_19_78)
* Rootfs used: [Buildroot 2020.02](/roadrunner_buildroot) 

## Kernel menuconfig

Enable the kernel SPI drivers as explained here:

* @article='roadrunner_spi'
 
Enable the Kernel support for small TFT LCD with ILI9341 LCD Controller

	Device Drivers  --->
      [*] Staging drivers  --->
        <*>   Support for small TFT LCD display modules  --->
		        <*>   FB driver for the ILI9341 LCD Controller 

## Example 1: One display on each SPI 

In this example we will use our [XTERM-01](/XTERM-01) wired to [Berta Board D2](/roadrunner#bertad2) 
evaluation kit using the port SPI0 and SPI1 lines (MOSI, MISO, CLK and CS) plus some 
extra signals required by the display (reset and data/command). 

<img width="520" src="./roadrunner_2spi_2tft.jpg"/><br/>


 	FIRST DISPLAY ON SPI0 	                SECOND DISPLAY

	| Signal     | Berta D2 | XTerm 0 |	  | Signal     | Berta D2 | XTerm 1 |
	|------------|----------|---------|   |------------|----------|---------|
	| SPI0 MOSI  | PA15     | J4.8    |   | SPI1 MOSI  | PC2      | J4.8    |
	| SPI0 MISO  | PA16     | J4.10   |   | SPI1 MISO  | PC3      | J4.10   |
	| SPI0 SCLK  | PA14     |  J4.7   |   | SPI1 SCLK  | PC1      | J4.7    |
	| SPI0 CS0   | PA17     | J4.25   |   | SPI1 CS0   | PC4      | J4.25   |
	|            |          |         |   |            |          |         |
	| Reset      | PA13     | J4.33   |   | Reset      | PC5      | J4.33   |
	| D/C        | PA12     | J4.31   |   | D/C        | PC6      | J4.31   |
	|            |          |         |   |            |          |         |
	| 3V3        | 3V3      |  J4.5   |   | 3V3        | 3V3      | J4.5    |
	| GND        | GND      |  J4.9   |   | GND        | GND      | J4.9    |
	!------------|----------|---------|   |------------|----------|---------|

Device tree definition

	/* Enable the SPI port 0 for a display selected by CS0 signal */

	spi0: spi@f8000000 {
		pinctrl-names = "default";
		pinctrl-0 = <&pinctrl_spi0_default>;
		status = "okay";

		device@0 {
			rotate = <90>;
			bgr;
			fps = <30>;
			compatible = "ilitek,ili9341";
			spi-max-frequency = <50000000>;   
			reg = <0>;
			regwidth = <8>;
			buswidth = <8>;
			verbose = <3>;
			reset-gpios = <&pioA PIN_PA13 0>;
			dc-gpios = <&pioA PIN_PA12 0>;
		};
	};


	/* Enable the SPI port 1 for a display selected by CS0 signal */

	spi1: spi@fc000000 {
		pinctrl-names = "default";
		pinctrl-0 = <&pinctrl_spi1_default>;
		status = "okay";

		device@0 {
			rotate = <90>;
			bgr;
			fps = <30>;
			compatible = "ilitek,ili9341";
			spi-max-frequency = <50000000>;   
			reg = <0>;
			regwidth = <8>;
			buswidth = <8>;
			verbose = <3>;
			reset-gpios = <&pioA PIN_PC5 0>;
			dc-gpios = <&pioA PIN_PC6 0>;
		};
	};

## Example 2: Two displays on the same each SPI 

In this example we will use our [XTERM-01](/XTERM-01) wired to [Berta Board D2](/roadrunner#bertad2) 
evaluation kit using the port SPI1 lines (MOSI, MISO, CLK, CS0 and CS1) plus some 
extra signals required by the display (reset and data/command). 

<img width="520" src="./roadrunner_1spi_2tft.jpg"/><br/>

The CS0 and CS1 signals will be used to select the display

	| Signal     | Berta D2 | XTerm 0 | XTerm 1 |
	|------------|----------|---------|---------|
	| SPI1 MOSI  | PC2      | J4.8    | J4.8    |
	| SPI1 MISO  | PC3      | J4.10   | J4.10   |
	| SPI1 SCLK  | PC1      | J4.7    | J4.7    |
    |            |          |         |         |
	| SPI1 CS0   | PC4      | J4.25   |         |
	| Reset  0   | PA13     | J4.33   |         |
	| D/C    0   | PA12     | J4.31   |         |
	|            |          |         |         |
	| SPI1 CS1   | PC5      |         | J4.25   |
	| Reset  1   | PA11     |         | J4.33   |
	| D/C    1   | PA8      |         | J4.31   |
	|            |          |         |         |
	| 3V3        | 3V3      | J4.5    | J4.5    |
	| GND        | GND      | J4.9    | J4.9    |
	!------------|----------|---------|---------|

Device tree definition

	/* Enable the SPI port 1 */

	spi1: spi@fc000000 {
		pinctrl-names = "default";
		pinctrl-0 = <&pinctrl_spi1_default>;
		status = "okay";

		/* Display 0 selected by CS0 */

		device@0 {
			rotate = <90>;
			bgr;
			fps = <30>;
			compatible = "ilitek,ili9341";
			spi-max-frequency = <50000000>;   
			reg = <0>;
			regwidth = <8>;
			buswidth = <8>;
			verbose = <3>;
			reset-gpios = <&pioA PIN_PA13 0>;
			dc-gpios = <&pioA PIN_PA12 0>;
		};

		/* Display 0 selected by CS1 */

		device@1 {
			rotate = <90>;
			bgr;
			fps = <30>;
			compatible = "ilitek,ili9341";
			spi-max-frequency = <50000000>;   
			reg = <1>;
			regwidth = <8>;
			buswidth = <8>;
			verbose = <3>;
			reset-gpios = <&pioA PIN_PA11 0>;
			dc-gpios = <&pioA PIN_PA8 0>;
		};
	};

## Frame buffer

The display will be managed by Linux using these two devices:

	/dev/fb0
	/dev/fb1
	
It will be initializated at startup. 

## Using QT5

The QT5 applications can select on which display send the output in this form:

	/usr/lib/qt/examples/widgets/widgets/calculator/calculator -platform linuxfb:fb=/dev/fb0 
	/usr/lib/qt/examples/widgets/widgets/calculator/calculator -platform linuxfb:fb=/dev/fb1 

<img src="./qt5_on_spi_display.jpg" width="520px">

<!--
## Other displays

* @article='roadrunner_fbtft_himax8347'
-->

## Links

* @article='roadrunner_spi'
* [Linux Framebuffer drivers for small TFT LCD display modules](https://github.com/notro/fbtft)
* @article='XTERM-01'
* [XTERM-01 Schematic](http://terzo.acmesystems.it/download/schematics/xterm-01_schematic.pdf)
* [IC ILI9341 datasheet](http://www.adafruit.com/datasheets/ILI9341.pdf)
* [Build a QT5 application on Buildroot](https://bootlin.com/blog/building-a-linux-system-for-the-stm32mp1-setting-up-a-qt5-application-development-environment/)

@include='adv_roadrunner'