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Need an example of  SPI- TFT touchscreen for pocketbegle

chrischristian14

Hi, I am after adding a touchscreen TFT display to pocketbeagle.

I am already using I/O in C via iobb library, so I am not sure if using a TFT LCD with fbtft driver will conflict with iobb.

There are lot of LCDs available for RPi which should work for pocketbeagle but I am not sure

- How to install fbtft driver - as a module, not built with kernel, I mean use insmod after bootup

- How to modify the driver to tell it to use a specific SPI connectors and how to make sure the driver doesn't mess up existing I/O configuration.

- What are the steps to redirect Xfce environment to the LCD

- And of course the hardware connection.

 

Thanks

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  • 0

    It seems pocketbeagle can't work with lcd because there is no GPU, so there is no way to have a full desktop environment on LCD.

    Should I use beaglebone instead ? I managed to get he VNC working and access the GUI desktop that way but, I really need LCD.

    Thanks

  • 0 in reply to chrischristian14

    After long time I managed to get back on to this project, I am trying

    https://github.com/danjulio/lepton/tree/master/pocketbeagle/littlevgl_demo

    with this LCD http://www.lcdwiki.com/2.8inch_RPi_Display

    I edited the demo c code in the first link to only initaliize LCD and not the touch screen, as I am first focusing only on the LCD part, however all I get the white blank screen (because of backlight), I am adding the modified main.c here

    #include "lvgl/lvgl.h"
#include "lv_drivers/display/fbdev.h"
#include "lv_drivers/indev/evdev.h"
#include "lv_examples/lv_apps/demo/demo.h"
#include <unistd.h>

#define DISP_BUF_SIZE (320*240*2)

int main(void)
{
	/*LittlevGL init*/
	lv_init();

	/*Linux frame buffer device init*/
	fbdev_init();

	/*Linux touchscreen device init*/
//	evdev_init();

	/*A small buffer for LittlevGL to draw the screen's content*/
	static lv_color_t buf1[DISP_BUF_SIZE];
	static lv_color_t buf2[DISP_BUF_SIZE];

	/*Initialize a descriptor for the buffer*/
	static lv_disp_buf_t disp_buf;
	lv_disp_buf_init(&disp_buf, buf1, buf2, DISP_BUF_SIZE);

	/*Initialize and register a display driver*/
	lv_disp_drv_t disp_drv;
	lv_disp_drv_init(&disp_drv);
	disp_drv.buffer = &disp_buf;
	disp_drv.flush_cb = fbdev_flush;
	lv_disp_drv_register(&disp_drv);

	/*Initialize and register an input device*/
	/*
	lv_indev_drv_t indev_drv;
	lv_indev_drv_init(&indev_drv);
	indev_drv.type = LV_INDEV_TYPE_POINTER;
	indev_drv.read_cb = evdev_read;
	lv_indev_t * my_indev = lv_indev_drv_register(&indev_drv);
	*/

	 /*Create demo*/
	demo_create();

	/*Handle LitlevGL tasks (tickless mode)*/
	while(1) {
		lv_tick_inc(5);
		lv_task_handler();
		usleep(5000);
	}

	return 0;
}

    Unfortunately I can't find a simple helloworld  over SPI for the LCD chip ILI9341 as mentioned before, that would have been a good start but the only example that is simple enough is the above one. The worst case would be to go through datasheet of ILI9341 and write the code from scratch.

    Can anyone please see the above link and my modified code ? If you have any tips it will be great before I start from scratch.

    p.s. : Upon running demo code I can see the framebuffer driver is loaded successfully, and I have checked the connections multiple times.

    Thanks

Reply
  • 0 in reply to chrischristian14

    After long time I managed to get back on to this project, I am trying

    https://github.com/danjulio/lepton/tree/master/pocketbeagle/littlevgl_demo

    with this LCD http://www.lcdwiki.com/2.8inch_RPi_Display

    I edited the demo c code in the first link to only initaliize LCD and not the touch screen, as I am first focusing only on the LCD part, however all I get the white blank screen (because of backlight), I am adding the modified main.c here

    #include "lvgl/lvgl.h"
#include "lv_drivers/display/fbdev.h"
#include "lv_drivers/indev/evdev.h"
#include "lv_examples/lv_apps/demo/demo.h"
#include <unistd.h>

#define DISP_BUF_SIZE (320*240*2)

int main(void)
{
	/*LittlevGL init*/
	lv_init();

	/*Linux frame buffer device init*/
	fbdev_init();

	/*Linux touchscreen device init*/
//	evdev_init();

	/*A small buffer for LittlevGL to draw the screen's content*/
	static lv_color_t buf1[DISP_BUF_SIZE];
	static lv_color_t buf2[DISP_BUF_SIZE];

	/*Initialize a descriptor for the buffer*/
	static lv_disp_buf_t disp_buf;
	lv_disp_buf_init(&disp_buf, buf1, buf2, DISP_BUF_SIZE);

	/*Initialize and register a display driver*/
	lv_disp_drv_t disp_drv;
	lv_disp_drv_init(&disp_drv);
	disp_drv.buffer = &disp_buf;
	disp_drv.flush_cb = fbdev_flush;
	lv_disp_drv_register(&disp_drv);

	/*Initialize and register an input device*/
	/*
	lv_indev_drv_t indev_drv;
	lv_indev_drv_init(&indev_drv);
	indev_drv.type = LV_INDEV_TYPE_POINTER;
	indev_drv.read_cb = evdev_read;
	lv_indev_t * my_indev = lv_indev_drv_register(&indev_drv);
	*/

	 /*Create demo*/
	demo_create();

	/*Handle LitlevGL tasks (tickless mode)*/
	while(1) {
		lv_tick_inc(5);
		lv_task_handler();
		usleep(5000);
	}

	return 0;
}

    Unfortunately I can't find a simple helloworld  over SPI for the LCD chip ILI9341 as mentioned before, that would have been a good start but the only example that is simple enough is the above one. The worst case would be to go through datasheet of ILI9341 and write the code from scratch.

    Can anyone please see the above link and my modified code ? If you have any tips it will be great before I start from scratch.

    p.s. : Upon running demo code I can see the framebuffer driver is loaded successfully, and I have checked the connections multiple times.

    Thanks

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