Added STM32 example.

examples/STM32_TFT_eSPI_Slider/Readme.md

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+Littlevgl on STM32F103C BluePill and ILI9341 in 8-Bit Parallel with XPT2046 Touch-pad on SPI2 port.
+Which able to dim an LED attached to PB6 Pin (thru 100to330 ohm series resistor from GND) by adjusting the slider.
+Library dependencies:
+1. TFT_eSPI https://github.com/Bodmer/TFT_eSPI
+  and choosing the right setup inside User_Setup_Select.h and also set right pins on selected user file.
+2.  TFT_eTouch.h    https://github.com/achillhasler/TFT_eTouch
+  and set the right pins inside TFT_eTouchUser.h and also run calibrate.ino to get the calibration value and store it inside
+  TFT_eTouchUser.h like #define TOUCH_DEFAULT_CALIBRATION { 294, 3913, 339, 3869, 2 }
+  Note that TFT_eSPI touch include extension does nether support second SPI port nor touch in parallel mode. 
+3. Installing the last master Arduino_Core_STM32 on https://github.com/stm32duino/Arduino_Core_STM32
+  because the Hardwaretimer definitions changed a bit in 1.9.0 version which about to release.
+4. lv_arduino https://github.com/littlevgl/lv_arduino
+  and config the lv_conf.h eg: 
+  #define LV_HOR_RES_MAX          (320)
+  #define LV_VER_RES_MAX          (240)
+  #define LV_USE_THEME_NIGHT      1   /*Dark elegant theme*/
+  #define LV_MEM_CUSTOM      1 // otherwise overfloe the flash on STM32F103CB
+
+![Example](https://github.com/HamidSaffari/lv_arduino/blob/master/examples/STM32_TFT_eSPI_Slider/photo_2020-04-02_01-55-36.jpg)
+
+
+  Created by Hamid Saffari @ Apr 2020. https://github.com/HamidSaffari/
+  Released into the public domain.

examples/STM32_TFT_eSPI_Slider/STM32_TFT_eSPI_Slider.ino

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+//Created by Hamid Saffari @ Apr 2020. https://github.com/HamidSaffari/ Released into the public domain.
+#include <SPI.h>
+#include <lvgl.h>
+#include <TFT_eSPI.h>
+#include <TFT_eTouch.h>  // https://github.com/achillhasler/TFT_eTouch
+
+/* using TFT_eTouch.h             : 106860 bytes (81%) FALSH,  13432 bytes (65%) RAM 
+   using TFT_eSPI.h touch include : 105096 bytes (80%) FALSH,  13392 bytes (65%) RAM 
+*/
+
+#define LED_PIN PB6
+#define LVGL_TICK_PERIOD 60
+
+//Ticker tick; /* timer for interrupt handler */
+TFT_eSPI tft = TFT_eSPI(); /* TFT instance */
+static lv_disp_buf_t disp_buf;
+static lv_color_t buf[LV_HOR_RES_MAX * 10];
+
+
+//TFT_eTouch<TFT_eSPI> touch(tft, TFT_ETOUCH_CS, 0xff, TFT_eSPI::getSPIinstance());
+SPIClass spi_touch(PB15, PB14, PB13);// SPIClass SPITwo(PB15, PB14, PB13); (MOSI, MISO, CLK)
+TFT_eTouch<TFT_eSPI> touch(tft, TFT_ETOUCH_CS, TFT_ETOUCH_PIRQ, spi_touch); 
+
+
+lv_obj_t * slider_label;
+int screenWidth = 320;
+int screenHeight = 240;
+
+
+/* By Bodmer in https://github.com/Bodmer/TFT_eSPI/issues/581
+   faster and more efficient than previous one: */
+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);
+
+  tft.startWrite();
+ #ifdef USE_DMA
+   tft.pushImageDMA(area->x1, area->y1, w, h, &color_p->full);
+   // Note: tft.endWrite(); must be called in my_lv_tick_handler when DMA is complete
+ #else
+   tft.setAddrWindow(area->x1, area->y1, w, h);
+   tft.pushColors(&color_p->full, w * h, true);
+   tft.endWrite();
+ #endif
+
+  lv_disp_flush_ready(disp);
+}
+
+bool my_touchpad_read(lv_indev_drv_t * indev_driver, lv_indev_data_t * data)
+{
+
+	int16_t touchX, touchY;
+	bool touched = touch.getXY(touchX, touchY);  //  bool TFT_eTouch<T>::getXY(int16_t& x, int16_t& y)
+
+    if(!touched)
+    {
+      return false;
+    }
+
+    if(touchX>screenWidth || touchY > screenHeight)
+    {
+      Serial.println("Y or y outside of expected parameters..");
+      Serial.print("y:");
+      Serial.print(touchX);
+      Serial.print(" x:");
+      Serial.print(touchY);
+    }
+    else
+    {
+
+      data->state = touched ? LV_INDEV_STATE_PR : LV_INDEV_STATE_REL; 
+
+      /*Save the state and save the pressed coordinate*/
+      //if(data->state == LV_INDEV_STATE_PR) touchpad_get_xy(&last_x, &last_y);
+
+      /*Set the coordinates (if released use the last pressed coordinates)*/
+      data->point.x = touchX;
+      data->point.y = touchY;
+
+      Serial.print("Data x");
+      Serial.println(touchX);
+
+      Serial.print("Data y");
+      Serial.println(touchY);
+
+    }
+
+    return false; /*Return `false` because we are not buffering and no more data to read*/
+}
+
+/* Interrupt driven periodic handler */
+static void lv_tick_handler(void)
+{
+  lv_tick_inc(LVGL_TICK_PERIOD);
+}
+
+void slider_event_cb(lv_obj_t * slider, lv_event_t event)
+{
+
+  printEvent("Slider", event);
+
+  if(event == LV_EVENT_VALUE_CHANGED) {
+      static char buf[4];                                 /* max 3 bytes  for number plus 1 null terminating byte */
+      snprintf(buf, 4, "%u", lv_slider_get_value(slider));
+      lv_label_set_text(slider_label, buf);               /*Refresh the text*/
+	  int16_t value = lv_slider_get_value(slider);
+	  value = map(value, 0, 100, 0, 255);
+	  //analogWriteFrequency(2000); // Set PMW period to 2000 Hz instead of 1000
+	  analogWrite(LED_PIN, value);//8-bit by default
+  }
+}
+
+void printEvent(String Event, lv_event_t event)
+{
+
+  Serial.print(Event);
+  Serial.printf(" ");
+
+  switch(event) {
+      case LV_EVENT_PRESSED:
+          Serial.printf("Pressed\n");
+          break;
+
+      case LV_EVENT_SHORT_CLICKED:
+          Serial.printf("Short clicked\n");
+          break;
+
+      case LV_EVENT_CLICKED:
+          Serial.printf("Clicked\n");
+          break;
+
+      case LV_EVENT_LONG_PRESSED:
+          Serial.printf("Long press\n");
+          break;
+
+      case LV_EVENT_LONG_PRESSED_REPEAT:
+          Serial.printf("Long press repeat\n");
+          break;
+
+      case LV_EVENT_RELEASED:
+          Serial.printf("Released\n");
+          break;
+  }
+}
+
+
+void setup() {
+
+  Serial.begin(115200); /* prepare for possible serial debug */
+  pinMode(LED_PIN, OUTPUT);
+
+  lv_init();
+
+  tft.begin(); /* TFT init */
+  tft.setRotation(1);
+
+  spi_touch.begin();
+  touch.init();
+
+/*  @brief  set measure
+  * @param drop_first ignore first n measures
+  * @param z_once read z1 and z2 only once. When this flag is true z_first must be also true.
+  * @param z_first when true start measure with Z1 otherwise with X
+  * @param z_local_min when true, get local minimum of RZ
+  * @param count how many values used by averaging or witch measure is taken. 0 means read until measure is equal last measure
+  *
+  *  inline void setMeasure(uint8_t drop_first = 0, bool z_once = false, bool z_first = false, bool z_local_min = false, uint8_t count = 0);
+*/
+  touch.setMeasure(0, false, true, false, 2); // z first, take 2'th z,x,y   // untouched: 35 us touched: 95 us
+
+  //touch.setMeasure(0, true, true, false, 1); // Differential mode fastest (each axis read only once, may work)
+  //touch.setAcurateDistance(25); // in this mode acurate distance must be higher for getUserCalibration (default 10)
+
+  lv_disp_buf_init(&disp_buf, buf, NULL, LV_HOR_RES_MAX * 10);
+
+  /*Initialize the display*/
+  lv_disp_drv_t disp_drv;
+  lv_disp_drv_init(&disp_drv);
+  disp_drv.hor_res = screenWidth;
+  disp_drv.ver_res = screenHeight;
+  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);             /*Descriptor of a input device driver*/
+  indev_drv.type = LV_INDEV_TYPE_POINTER;    /*Touch pad is a pointer-like device*/
+  indev_drv.read_cb = my_touchpad_read;      /*Set your driver function*/
+  lv_indev_drv_register(&indev_drv);         /*Finally register the driver*/
+
+
+  /*Initialize the graphics library's tick*/
+  ////tick.attach_ms(LVGL_TICK_PERIOD, lv_tick_handler);
+
+  TIM_TypeDef *Instance = TIM2;
+  // Instantiate HardwareTimer object. Thanks to 'new' instanciation, HardwareTimer is not destructed when setup() function is finished.
+  HardwareTimer *MyTim = new HardwareTimer(Instance);
+  //MyTim->setMode(2, TIMER_OUTPUT_COMPARE);
+  MyTim->setOverflow(LVGL_TICK_PERIOD*1000, MICROSEC_FORMAT);
+  MyTim->attachInterrupt(lv_tick_handler);
+  MyTim->resume();
+
+  //Set the theme..
+  lv_theme_t * th = lv_theme_night_init(210, NULL);     //Set a HUE value and a Font for the Night Theme
+  lv_theme_set_current(th);
+
+  lv_obj_t * scr = lv_cont_create(NULL, NULL);
+  lv_disp_load_scr(scr);
+
+  //lv_obj_t * tv = lv_tabview_create(scr, NULL);
+  //lv_obj_set_size(tv, lv_disp_get_hor_res(NULL), lv_disp_get_ver_res(NULL));
+
+  /* Create simple label */
+  lv_obj_t *label = lv_label_create(lv_scr_act(), NULL);
+  lv_label_set_text(label, "PB6 LED DIMMER");
+  lv_obj_align(label, NULL, LV_ALIGN_CENTER, 0, -50);
+
+  /* Create a slider in the center of the display */
+  lv_obj_t * slider = lv_slider_create(lv_scr_act(), NULL);
+  lv_obj_set_width(slider, screenWidth-50);                        /*Set the width*/
+  lv_obj_set_height(slider, 50);
+  lv_obj_align(slider, NULL, LV_ALIGN_CENTER, 0, 0);    /*Align to the center of the parent (screen)*/
+  lv_obj_set_event_cb(slider, slider_event_cb);         /*Assign an event function*/
+
+  /* Create a label below the slider */
+  slider_label = lv_label_create(lv_scr_act(), NULL);
+  lv_label_set_text(slider_label, "0");
+  lv_obj_set_auto_realign(slider, true);
+  lv_obj_align(slider_label, slider, LV_ALIGN_OUT_BOTTOM_MID, 0, 10);
+
+}
+
+void loop() {
+
+  lv_task_handler(); /* let the GUI do its work */
+  delay(5);
+}