Display flickers when ESP32 is in AP mode

[eddeyonline]

I've noticed a consistent issue with the display flickering when the ESP32 is in AP or APSTA mode. I'm using a 240x320 2.4" TFT LCD from AliExpress with ILI9341 display driver and XPT2046 touch driver. The display works perfectly when wifi is not enabled or when the ESP32 is connected in STA mode. As soon as it is in AP or APSTA mode, without changing any other factors or connecting to the AP, the display has a constant flicker (maybe 20-30Hz just by looking at it). Any ideas on how to resolve this issue? Thanks!

[C47D]

Hi,

Could you upload some code to replicate it? Are you using master?

Regards
Carlos

[eddeyonline]

/* LVGL Example project
*

• Basic project to test LVGL on ESP32 based projects.
• This example code is in the Public Domain (or CC0 licensed, at your option.)
• Unless required by applicable law or agreed to in writing, this
• software is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
• CONDITIONS OF ANY KIND, either express or implied.
  */

// Change whether AP or STA mode with define at line 55, note flicker in AP mode
// Fill in SSID and password for STA mode at lines 85-86

#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "freertos/queue.h"
#include "freertos/event_groups.h"
#include "esp_event.h"

#include "esp_wifi.h"
#include "esp_log.h"
#include "esp_event_loop.h" //might not need this
#include "nvs_flash.h"
#include "esp_freertos_hooks.h"
#include "esp_system.h"

/* Littlevgl specific */
#include "lvgl/lvgl.h"

#include "disp_spi.h"
#include "disp_driver.h"
#include "tp_spi.h"
#include "touch_driver.h"

/*********************

•  DEFINES
  

*********************/

#define MODE_AP_STA 0 //if this is 0 ESP32 will boot in AP mode, 1 will boot in STA mode

// Detect the use of a shared SPI Bus and verify the user specified the same SPI bus for both touch and tft
#if (CONFIG_LVGL_TOUCH_CONTROLLER == 1 || CONFIG_LVGL_TOUCH_CONTROLLER == 3) && TP_SPI_MOSI == DISP_SPI_MOSI && TP_SPI_CLK == DISP_SPI_CLK
#if CONFIG_LVGL_TFT_DISPLAY_SPI_HSPI == 1
#define TFT_SPI_HOST HSPI_HOST
#else
#define TFT_SPI_HOST VSPI_HOST
#endif

#if CONFIG_LVGL_TOUCH_CONTROLLER_SPI_HSPI == 1
#define TOUCH_SPI_HOST HSPI_HOST
#else
#define TOUCH_SPI_HOST VSPI_HOST
#endif

#if TFT_SPI_HOST != TOUCH_SPI_HOST
#error You must specifiy the same SPI host for both display and input driver
#endif

#define SHARED_SPI_BUS
#endif

#define EXAMPLE_ESP_MAXIMUM_RETRY 5
// FreeRTOS event group to signal when we are connected
static EventGroupHandle_t s_wifi_event_group;
/* The event group allows multiple bits for each event, but we only care about two events:

• • we are connected to the AP with an IP
• • we failed to connect after the maximum amount of retries */
    #define WIFI_CONNECTED_BIT BIT0
    #define WIFI_FAIL_BIT BIT1

#if MODE_AP_STA == 0
#define EXAMPLE_ESP_WIFI_SSID "wifi_test"
#define EXAMPLE_ESP_WIFI_PASS "password"
#define EXAMPLE_MAX_STA_CONN 4
static const char *TAG = "wifi AP mode";
#else
#define SSID "yourSSID"
#define PASS "yourPassword"
static const char *TAG = "wifi STA mode";
#endif

static int s_retry_num = 0;

/**********************

• STATIC PROTOTYPES
  **********************/
  static void IRAM_ATTR lv_tick_task(void);

#ifdef SHARED_SPI_BUS
/* Example function that configure two spi devices (tft and touch controllers) into the same spi bus */
static void configure_shared_spi_bus(void);
#endif

static void btn_event_cb(lv_obj_t * btn, lv_event_t event);

/**********************

• STATIC VARIABLES
  **********************/

static lv_obj_t * cont;

/**********************

• STATIC FUNCTIONS
  **********************/

/**

• Called when a button is released
• @param btn pointer to the released button
• @param event the triggering event
• @return LV_RES_OK because the object is not deleted in this function
  */
  static void btn_event_cb(lv_obj_t * btn, lv_event_t event)
  {
  if(event == LV_EVENT_RELEASED) {
  lv_obj_t * label = lv_label_create(cont, NULL);
  lv_obj_t * btnLabel = lv_obj_get_child(btn, NULL);
  const char * txt = lv_label_get_text(btnLabel);
  printf("%s button pressed", txt);
  printf("button was pressed\n");
  lv_label_set_text(label, "Button Pressed");
  }
  }

static void event_handler(void* arg, esp_event_base_t event_base,
int32_t event_id, void* event_data)
{
if (event_base == WIFI_EVENT && event_id == WIFI_EVENT_STA_START) {
esp_wifi_connect();
} else if (event_base == WIFI_EVENT && event_id == WIFI_EVENT_STA_DISCONNECTED) {
if (s_retry_num < EXAMPLE_ESP_MAXIMUM_RETRY) {
esp_wifi_connect();
s_retry_num++;
ESP_LOGI(TAG, "retry to connect to the AP");
} else {
xEventGroupSetBits(s_wifi_event_group, WIFI_FAIL_BIT);
}
ESP_LOGI(TAG,"connect to the AP fail");
} else if (event_base == IP_EVENT && event_id == IP_EVENT_STA_GOT_IP) {
ip_event_got_ip_t* event = (ip_event_got_ip_t*) event_data;
ESP_LOGI(TAG, "got ip:%s",
ip4addr_ntoa(&event->ip_info.ip));
s_retry_num = 0;
xEventGroupSetBits(s_wifi_event_group, WIFI_CONNECTED_BIT);
}
if (event_id == WIFI_EVENT_AP_STACONNECTED) {
wifi_event_ap_staconnected_t* event = (wifi_event_ap_staconnected_t*) event_data;
ESP_LOGI(TAG, "station "MACSTR" join, AID=%d",
MAC2STR(event->mac), event->aid);
} else if (event_id == WIFI_EVENT_AP_STADISCONNECTED) {
wifi_event_ap_stadisconnected_t* event = (wifi_event_ap_stadisconnected_t*) event_data;
ESP_LOGI(TAG, "station "MACSTR" leave, AID=%d",
MAC2STR(event->mac), event->aid);
}
}
void wifi_init_sta()
{
s_wifi_event_group = xEventGroupCreate();

tcpip_adapter_init();

ESP_ERROR_CHECK(esp_event_loop_create_default());

wifi_init_config_t cfg = WIFI_INIT_CONFIG_DEFAULT();
ESP_ERROR_CHECK(esp_wifi_init(&cfg));

ESP_ERROR_CHECK(esp_event_handler_register(WIFI_EVENT, ESP_EVENT_ANY_ID, &event_handler, NULL));
ESP_ERROR_CHECK(esp_event_handler_register(IP_EVENT, IP_EVENT_STA_GOT_IP, &event_handler, NULL));

#if MODE_AP_STA == 0
wifi_config_t ap_wifi_config = {
.ap = {
.ssid = EXAMPLE_ESP_WIFI_SSID,
.ssid_len = strlen(EXAMPLE_ESP_WIFI_SSID),
.password = EXAMPLE_ESP_WIFI_PASS,
.max_connection = EXAMPLE_MAX_STA_CONN,
.authmode = WIFI_AUTH_WPA_WPA2_PSK
},
};

if (strlen(EXAMPLE_ESP_WIFI_PASS) == 0) {
    ap_wifi_config.ap.authmode = WIFI_AUTH_OPEN;
}
ESP_ERROR_CHECK(esp_wifi_set_mode(WIFI_MODE_AP) ); 
ESP_ERROR_CHECK(esp_wifi_set_config(ESP_IF_WIFI_AP, &ap_wifi_config) );

#else
wifi_config_t sta_wifi_config = {
.sta = {
.ssid = SSID,
.password = PASS
},
};
ESP_ERROR_CHECK(esp_wifi_set_mode(WIFI_MODE_STA) );
ESP_ERROR_CHECK(esp_wifi_set_config(ESP_IF_WIFI_STA, &sta_wifi_config) );
#endif

ESP_ERROR_CHECK(esp_wifi_start() );

#if MODE_AP_STA == 0
ESP_LOGI(TAG, "Soft AP initialised. SSID:%s password:%s",
EXAMPLE_ESP_WIFI_SSID, EXAMPLE_ESP_WIFI_PASS);
#else
/* Waiting until either the connection is established (WIFI_CONNECTED_BIT) or connection failed for the maximum
* number of re-tries (WIFI_FAIL_BIT). The bits are set by event_handler() (see above) */
EventBits_t bits = xEventGroupWaitBits(s_wifi_event_group,
WIFI_CONNECTED_BIT | WIFI_FAIL_BIT,
pdFALSE,
pdFALSE,
portMAX_DELAY);

/* xEventGroupWaitBits() returns the bits before the call returned, hence we can test which event actually
 * happened. */
if (bits & WIFI_CONNECTED_BIT) {
    ESP_LOGI(TAG, "connected to ap SSID:%s password:%s",
             SSID, PASS);
} else if (bits & WIFI_FAIL_BIT) {
    ESP_LOGI(TAG, "Failed to connect to SSID:%s, password:%s",
             SSID, PASS);
} else {
    ESP_LOGE(TAG, "UNEXPECTED EVENT");
}
vEventGroupDelete(s_wifi_event_group);

#endif

ESP_ERROR_CHECK(esp_event_handler_unregister(IP_EVENT, IP_EVENT_STA_GOT_IP, &event_handler));
ESP_ERROR_CHECK(esp_event_handler_unregister(WIFI_EVENT, ESP_EVENT_ANY_ID, &event_handler));   

}

void lv_tutorial_objects(void)
{

/********************
 * CREATE A SCREEN
 *******************/
/* Create a new screen and load it
 * Screen can be created from any type object type
 * Now a Page is used which is an objects with scrollable content*/
static lv_style_t style;
lv_style_copy(&style, &lv_style_plain);
style.body.main_color = LV_COLOR_BLUE;
style.body.grad_color = LV_COLOR_BLUE;
style.text.color = LV_COLOR_WHITE;
lv_obj_t * scr = lv_page_create(NULL, NULL);
lv_page_set_style(scr, LV_PAGE_STYLE_BG, &style);
lv_page_set_style(scr, LV_PAGE_STYLE_SCRL, &style);
lv_page_set_sb_mode(scr, LV_SB_MODE_OFF);
lv_disp_load_scr(scr);

/****************
 * ADD A TITLE
 ****************/
lv_obj_t * label = lv_label_create(scr, NULL); /*First parameters (scr) is the parent*/
lv_label_set_text(label, "Test for flickering");  /*Set the text*/
lv_obj_set_x(label, 30);                        /*Set the x coordinate*/

/****************
 * ADD A STATUS FIELD
 ****************/

cont = lv_cont_create(lv_scr_act(), NULL);              //Global static definition so accessible in CB
lv_obj_set_auto_realign(cont, true);                    /*Auto realign when the size changes*/
lv_obj_align_origo(cont, NULL, LV_ALIGN_CENTER, 0, 0);  /*This parametrs will be sued when realigned*/
lv_cont_set_fit(cont, LV_FIT_TIGHT);
lv_cont_set_layout(cont, LV_LAYOUT_COL_M);

label = lv_label_create(cont, NULL);
#if MODE_AP_STA == 0
lv_label_set_text(label, "AP MODE");
#else
lv_label_set_text(label, "STA MODE");
#endif


/***********************
 * CREATE TWO BUTTONS
 ***********************/
/*Create a button*/
lv_obj_t * btn1 = lv_btn_create(lv_disp_get_scr_act(NULL), NULL);         /*Create a button on the currently loaded screen*/
lv_obj_set_event_cb(btn1, btn_event_cb);                                  /*Set function to be called when the button is released*/
lv_obj_align(btn1, scr, LV_ALIGN_IN_BOTTOM_LEFT, 0, 0);               /*Align below the label*/

/*Create a label on the button (the 'label' variable can be reused)*/
label = lv_label_create(btn1, NULL);
lv_label_set_text(label, "<--");

/*Copy the previous button*/
lv_obj_t * btn2 = lv_btn_create(scr, btn1);                 /*Second parameter is an object to copy*/
lv_obj_align(btn2, scr, LV_ALIGN_IN_BOTTOM_RIGHT, 0, 0);    /*Align next to the prev. button.*/

/*Create a label on the button*/
label = lv_label_create(btn2, NULL);
lv_label_set_text(label, "-->");

}

void app_main() {
//Initialize NVS
const static char* TAG = "app_main";
esp_err_t ret = nvs_flash_init();
if (ret == ESP_ERR_NVS_NO_FREE_PAGES || ret == ESP_ERR_NVS_NEW_VERSION_FOUND) {
ESP_ERROR_CHECK(nvs_flash_erase());
ret = nvs_flash_init();
}
ESP_ERROR_CHECK(ret);

ESP_LOGI(TAG, "ESP_WIFI_MODE_STA");
wifi_init_sta();

lv_init();

/* Interface and driver initialization /
#ifdef SHARED_SPI_BUS
/ Configure one SPI bus for the two devices */
configure_shared_spi_bus();

/* Configure the drivers /
disp_driver_init(false);
#if CONFIG_LVGL_TOUCH_CONTROLLER != TOUCH_CONTROLLER_NONE
touch_driver_init(false);
#endif
#else
/ Otherwise configure the SPI bus and devices separately inside the drivers*/
disp_driver_init(true);
#if CONFIG_LVGL_TOUCH_CONTROLLER != TOUCH_CONTROLLER_NONE
touch_driver_init(true);
#endif
#endif

static lv_color_t buf1[DISP_BUF_SIZE];
static lv_color_t buf2[DISP_BUF_SIZE];
static lv_disp_buf_t disp_buf;
lv_disp_buf_init(&disp_buf, buf1, buf2, DISP_BUF_SIZE);

lv_disp_drv_t disp_drv;
lv_disp_drv_init(&disp_drv);
disp_drv.flush_cb = disp_driver_flush;
disp_drv.buffer = &disp_buf;
lv_disp_drv_register(&disp_drv);

#if CONFIG_LVGL_TOUCH_CONTROLLER != TOUCH_CONTROLLER_NONE
lv_indev_drv_t indev_drv;
lv_indev_drv_init(&indev_drv);
indev_drv.read_cb = touch_driver_read;
indev_drv.type = LV_INDEV_TYPE_POINTER;
lv_indev_drv_register(&indev_drv);
#endif

esp_register_freertos_tick_hook(lv_tick_task);

lv_tutorial_objects();

while (1) {
vTaskDelay(1);
lv_task_handler();
}

}

static void IRAM_ATTR lv_tick_task(void) {
lv_tick_inc(portTICK_RATE_MS);
}

#ifdef SHARED_SPI_BUS
static void configure_shared_spi_bus(void)
{
/* Shared SPI bus configuration */
spi_bus_config_t buscfg = {
.miso_io_num = TP_SPI_MISO,
.mosi_io_num = DISP_SPI_MOSI,
.sclk_io_num = DISP_SPI_CLK,
.quadwp_io_num = -1,
.quadhd_io_num = -1,
#if CONFIG_LVGL_TFT_DISPLAY_CONTROLLER == TFT_CONTROLLER_ILI9341
.max_transfer_sz = DISP_BUF_SIZE * 2,
#elif CONFIG_LVGL_TFT_DISPLAY_CONTROLLER == TFT_CONTROLLER_ST7789
.max_transfer_sz = DISP_BUF_SIZE * 2,
#elif CONFIG_LVGL_TFT_DISPLAY_CONTROLLER == TFT_CONTROLLER_ILI9488
.max_transfer_sz = DISP_BUF_SIZE * 3,
#elif CONFIG_LVGL_TFT_DISPLAY_CONTROLLER == TFT_CONTROLLER_HX8357
.max_transfer_sz = DISP_BUF_SIZE * 2
#endif
};

esp_err_t ret = spi_bus_initialize(TFT_SPI_HOST, &buscfg, 1);
assert(ret == ESP_OK);

/* SPI Devices */
disp_spi_add_device(TFT_SPI_HOST);
tp_spi_add_device(TOUCH_SPI_HOST);
}
#endif

[eddeyonline]

That didn't format too well! I'll just email you Carlos.

[C47D]

Could you create a repo with it?

[eddeyonline]

I've never done that before, but I'll give it a go!

…

On Mon, 6 Apr 2020, 02:06 Carlos Diaz, ***@***.***> wrote: Could you create a repo with it? — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#92 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AO2H6Z6HL7XOZVOLREW4U6DRLCUCFANCNFSM4L55C5LQ> .

[eddeyonline]

Repo:
https://github.com/eddeyonline/lv_port_esp32_flickering.git

[C47D]

Thanks for the repo @eddeyonline, I will take a look at it.

[KammutierSpule]

Is the flickering brightness change (a possible hardware power supply issue) or pixel filling flickering?

[eddeyonline]

I don't think it's a power issue as changing power supply doesn't make a difference and it doesn't flicker when under load in STA mode.
I've just switched from using VSPI to HSPI to see if that made a difference but the issue is the same.
I've tried videoing the display in the two different modes to demonstrate the issue, but the flickering isn't apparent on the video.
Is anyone else noting this issue at all?

[stale]

This issue or pull request has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.