Inverted screen and colors

AghilesY · August 8, 2023, 8:42pm

Hi, I’m new to lvgl and I’m recreating someone’s project displaying a custom UI on a colmi p8 smart watch: GitHub - atc1441/ATCwatch: Custom Arduino C++ firmware for the P8 and PineTime plus many more DaFit Smartwatches

I’m using the portable Arduino IDE version which uses lv_arduino version 2.1.5 library.

So here is the problem:

The UI display is flipped from left to right(around Y axis), but the touch functionalities are not flipped (to access an icon on the right side I must touch the left side of the screen.
Colors are inverted: white is supposed to be black and green is supposed to be red etc.

So I tried tweaking the display.cpp file a bit but couldn’t get any results. I was wondering if it was possible to completely change the direction of X axis for the display only and invert colors.

Here is a picture of what I see:

VS what I should see:

Thanks!

Tinus · August 9, 2023, 5:56am

Hello, there’s a setting in the LVGL config lv_conf.h file:

/*Swap the 2 bytes of RGB565 color. Useful if the display has an 8-bit interface (e.g. SPI)*/
#define LV_COLOR_16_SWAP 0

which might do the trick?
Otherwise you may want to change the flushing function: as far as I know LVGL always stores the colors in RGB order with the given color depth (8, 16, 32-bit). So in the display flush function you may want to change the order in which the colors are written.

Marian_M · August 9, 2023, 4:40pm

LV16SWAP isnt problem source here maybe colours , but primary need solve mirror.
Show your code for disp flush callback. Maybe too MADCTL in driver registers isnt correct.

AghilesY · August 9, 2023, 4:47pm

Here are both display.h and display.cpp file of the project.

display.h:
#pragma once

#include “Arduino.h”
#include “pinout.h”

#define ST77XX_SLPIN 0x10
#define ST77XX_SLPOUT 0x11
#define ST77XX_DISPOFF 0x28
#define ST77XX_DISPON 0x29

void init_display();
void display_enable(bool state);
void inc_tick();

void setAddrWindowDisplay(uint32_t x, uint32_t y, uint32_t w, uint32_t h);
void initDisplay();
void spiCommand(uint8_t d);
void startWrite_display(void);
void endWrite_display(void);

display.cpp:
#include “display.h”

#include <lvgl.h>
#include “fast_spi.h”
#include “images.h”
#include “battery.h”
#include “touch.h”
#include “accl.h”
#include “menu.h”
#include “ble.h”
#include “heartrate.h”
#include “backlight.h”
#include “inputoutput.h”
#include “bootloader.h”
#include “time.h”
#include “push.h”

#define buffer_lcd_size LV_HOR_RES_MAX * 30
static lv_disp_buf_t disp_buf;
static lv_color_t buf[buffer_lcd_size];

void my_disp_flush(lv_disp_drv_t *disp, const lv_area_t *area, lv_color_t *color_p)
{
uint32_t w = (area->x2 - area->x1 + 1);
uint32_t h = (area->y2 - area->y1 + 1);
startWrite_display();
setAddrWindowDisplay(area->x1, area->y1, w, h);
write_fast_spi(reinterpret_cast<const uint8_t *>(color_p), (w * h * 2));
endWrite_display();
lv_disp_flush_ready(disp);
}

bool my_touchpad_read(lv_indev_drv_t * indev_driver, lv_indev_data_t * data)
{
bool touched = false;
touch_data_struct touch_data;
if (swipe_enabled()) {
get_read_touch();
touch_data = get_touch();
touched = (touch_data.event == 2) ? LV_INDEV_STATE_PR : LV_INDEV_STATE_REL;
get_new_touch_interrupt();
} else {
if (get_new_touch_interrupt()) {
touch_data = get_touch();
touched = (touch_data.gesture == TOUCH_SINGLE_CLICK) ? LV_INDEV_STATE_PR : LV_INDEV_STATE_REL;
} else {
touched = LV_INDEV_STATE_REL;
}
}
data->state = touched;
data->point.x = touch_data.xpos;
data->point.y = touch_data.ypos;
return false;
}

void inc_tick() {
lv_tick_inc(40);
}

void init_display() {
initDisplay();
lv_init();
lv_disp_buf_init(&disp_buf, buf, NULL, buffer_lcd_size);

lv_disp_drv_t disp_drv;
lv_disp_drv_init(&disp_drv);
disp_drv.hor_res = 240;
disp_drv.ver_res = 240;
disp_drv.flush_cb = my_disp_flush;
disp_drv.buffer = &disp_buf;
lv_disp_drv_register(&disp_drv);

lv_indev_drv_t indev_drv;
lv_indev_drv_init(&indev_drv);
indev_drv.type = LV_INDEV_TYPE_POINTER;
indev_drv.read_cb = my_touchpad_read;

lv_indev_drv_register(&indev_drv);

lv_theme_t *th = lv_theme_night_init(10, NULL);
lv_theme_set_current(th);
}

void display_enable(bool state) {
uint8_t temp[2];
startWrite_display();
if (state) {
spiCommand(ST77XX_DISPON);
spiCommand(ST77XX_SLPOUT);
} else {
spiCommand(ST77XX_SLPIN);
spiCommand(ST77XX_DISPOFF);
}
endWrite_display();
}

void setAddrWindowDisplay(uint32_t x, uint32_t y, uint32_t w, uint32_t h)
{
uint8_t temp[4];
//y += 180; // when rotated screen

spiCommand(0x2A);
temp[0] = (x >> 8);
temp[1] = x;
temp[2] = ((x + w - 1) >> 8);
temp[3] = (x + w - 1);
write_fast_spi(temp, 4);
spiCommand(0x2B);
temp[0] = (y >> 8 );
temp[1] = y;
temp[2] = ((y + h - 1) >> 8);
temp[3] = ((y + h - 1) & 0xFF);
write_fast_spi(temp, 4);
spiCommand(0x2C);
}

void initDisplay() {
uint8_t temp[25];
pinMode(LCD_CS, OUTPUT);
pinMode(LCD_RS, OUTPUT);
pinMode(LCD_RESET, OUTPUT);
pinMode(LCD_DET, OUTPUT);

digitalWrite(LCD_CS , HIGH);
digitalWrite(LCD_RS , HIGH);

digitalWrite(LCD_RESET, HIGH);
delay(20);
digitalWrite(LCD_RESET, LOW);
delay(100);
digitalWrite(LCD_RESET, HIGH);
delay(100);
startWrite_display();
spiCommand(54);
temp[0] = 0x00;//0xC0;// when rotated screen
write_fast_spi(temp, 1);
spiCommand(58);
temp[0] = 5;
write_fast_spi(temp, 1);
spiCommand(178);
temp[0] = 12;
temp[1] = 12;
temp[2] = 0;
temp[3] = 51;
temp[4] = 51;
write_fast_spi(temp, 5);
spiCommand(183);
temp[0] = 53;
write_fast_spi(temp, 1);
spiCommand(187);
temp[0] = 25;
write_fast_spi(temp, 1);
spiCommand(192);
temp[0] = 44;
write_fast_spi(temp, 1);
spiCommand(194);
temp[0] = 1;
write_fast_spi(temp, 1);
spiCommand(195);
temp[0] = 18;
write_fast_spi(temp, 1);
spiCommand(196);
temp[0] = 32;
write_fast_spi(temp, 1);
spiCommand(198);
temp[0] = 15;
write_fast_spi(temp, 1);
spiCommand(208);
temp[0] = 164;
temp[1] = 161;
write_fast_spi(temp, 2);
spiCommand(224);
temp[0] = 208;
temp[1] = 4;
temp[2] = 13;
temp[3] = 17;
temp[4] = 19;
temp[5] = 43;
temp[6] = 63;
temp[7] = 84;
temp[8] = 76;
temp[9] = 24;
temp[10] = 13;
temp[11] = 11;
temp[12] = 31;
temp[13] = 35;
write_fast_spi(temp, 14);
spiCommand(225);
temp[0] = 208;
temp[1] = 4;
temp[2] = 12;
temp[3] = 17;
temp[4] = 19;
temp[5] = 44;
temp[6] = 63;
temp[7] = 68;
temp[8] = 81;
temp[9] = 47;
temp[10] = 31;
temp[11] = 31;
temp[12] = 32;
temp[13] = 35;
write_fast_spi(temp, 14);
spiCommand(33);
spiCommand(17);
delay(120);
spiCommand(41);
spiCommand(0x11);
spiCommand(0x29);
endWrite_display();
}

void spiCommand(uint8_t d) {
digitalWrite(LCD_RS , LOW);
write_fast_spi(&d, 1);
digitalWrite(LCD_RS , HIGH);
}

void startWrite_display(void) {
enable_spi(true);
digitalWrite(LCD_CS , LOW);
}

void endWrite_display(void) {
digitalWrite(LCD_CS , HIGH);
enable_spi(false);
}

Marian_M · August 9, 2023, 5:03pm

This code is pretty unreadable without comments. Try read and inspire here TFT_eSPI/TFT_Drivers/ST7735_Init.h at master · Bodmer/TFT_eSPI · GitHub

And test and check if color format and MADCTL reg in your code 54 set right values.

#define TFT_MADCTL  0x36
#define TFT_MAD_MY  0x80
#define TFT_MAD_MX  0x40
#define TFT_MAD_MV  0x20
#define TFT_MAD_ML  0x10
#define TFT_MAD_BGR 0x08
#define TFT_MAD_MH  0x04
#define TFT_MAD_RGB 0x00

AghilesY · August 9, 2023, 7:16pm

Sorry to annoy, but in which file do you find those registers?

AghilesY · August 9, 2023, 8:16pm

Ended up finding out. It looks like it isn’t a register problem.

In Adafruit_ST7735.h I got:

#define ST7735_MADCTL 0x36

In Adafruit_ST7735.cpp I got:

#define MADCTL_MY  0x80
#define MADCTL_MX  0x40
#define MADCTL_MV  0x20
#define MADCTL_ML  0x10
#define MADCTL_RGB 0x08
#define MADCTL_MH  0x04

Marian_M · August 9, 2023, 8:53pm

Yes and in your init you can use defines or numbers. 0x36 = 54
And test changing for example
temp[0] = MADCTL_MX | TFT_MAD_BGR;

AghilesY · August 10, 2023, 1:14am

We got some progress thanks!
So I changed this part of code for:

  spiCommand(0x36);
  temp[0] = 0x40|0x08;//0x00;//0xC0;// when rotated screen
  write_fast_spi(temp, 1);

and it fixed the mirroring problem. But the inverted colors remain, I tried changing

#define LV_COLOR_16_SWAP

and it was just making some textures rainbow like in this picture:

Tinus · August 10, 2023, 6:19am

Hello, I am just trying to understand your code here. I still think the flush function is the issue but I have never worked with SPI displays before so its hard to figure out whats wrong. I’ve copy-pasted your code and formatted it a bit.
I suspect the flush function because I once had this issue too, and it was simply because I wrote the colors to the screen in the wrong order. BGR instead of RGB and vice versa.

void my_disp_flush(lv_disp_drv_t *disp, const lv_area_t *area, lv_color_t *color_p)
{
  uint32_t w = (area->x2 - area->x1 + 1); //Probably correct? Placement of pixels seems fine
  uint32_t h = (area->y2 - area->y1 + 1); //Probably correct? Placement of pixels seems fine

  startWrite_display(); //Understood.
  setAddrWindowDisplay(area->x1, area->y1, w, h); //what does this do?

  /*This line is probably the issue! */
  write_fast_spi(reinterpret_cast<const uint8_t *>(color_p), (w * h * 2));

  endWrite_display(); //Understood.
  lv_disp_flush_ready(disp); //Understood.
}

Am I correct in saying that this function sets the start x and y drawing positions in SPI?

void setAddrWindowDisplay(uint32_t x, uint32_t y, uint32_t w, uint32_t h)
{
  uint8_t temp[4];
  //y += 180; // when rotated screen
  
  spiCommand(0x2A);
  temp[0] = (x >> 8);
  temp[1] = x;
  temp[2] = ((x + w - 1) >> 8);
  temp[3] = (x + w - 1);
  write_fast_spi(temp, 4);
  spiCommand(0x2B);
  temp[0] = (y >> 8 );
  temp[1] = y;
  temp[2] = ((y + h - 1) >> 8);
  temp[3] = ((y + h - 1) & 0xFF);
  write_fast_spi(temp, 4);
  spiCommand(0x2C);
}

So, I figure this is the problem

  write_fast_spi(reinterpret_cast<const uint8_t *>(color_p), (w * h * 2));

Could you explain what this function does?

Marian_M · August 10, 2023, 1:23pm

Try locate in initdisplay command for invert display . If exist remove it , if not add…
And try 0x40 alone too.

I locate it for you
spiCommand(33);
change to
spiCommand(32);

AghilesY · August 11, 2023, 12:05am

Thank you so much it works!
0x40 alone indeed gives the best results and I modified to spiCommand(40) by error and it fixed the color inversion just like spiCommand(32).

AghilesY · August 11, 2023, 12:07am

To be honest I don’t even know myself. As I said previously, this code is taken from someone else’s project (which you can find in my first message).

Tinus · August 11, 2023, 6:12am

All right… Well, good to hear it works.