tft voltmeter example for STM32f429 discovery added

STM32/libraries/BoardExamples/examples/Discovery429ZI/TFT/Voltmeter/Voltmeter.ino

@@ -0,0 +1,69 @@
+/************************************************************************
+
+  STM32F429 Discovery Voltmeter 
+
+  Read the voltage on the ADC and show it on the TFT display.
+
+  Be careful:
+
+  ! Do not attache more than 3.3V to the analog input !
+
+  Sept. 2017, ChrisMicro
+
+  Remark: at the moment only the ADC connected to PA0 seems to return
+  useful values. PA0 is connected to the blue button on the board.
+
+************************************************************************/
+
+#include "LTDC_F429_Discovery.h"
+
+LTDC_F429_Discovery tft;
+
+#define ANALOG_SIGNAL_INPUT PA0
+
+void setup()
+{
+  tft.begin();
+  tft.fillScreen( LTDC_BLACK );
+ 
+  //tft.setRotation(0); // horitzontal wide screen
+}
+
+#define SAMPLING_TIME_MS 1000
+
+void loop(void)
+{
+  float    adcValue = 0;
+  uint32_t counts   = 0;
+  uint32_t endTime;
+  
+  // filter the signal
+  // mean value over a period 
+  endTime= millis() + SAMPLING_TIME_MS;
+  while(millis()<endTime)
+  {
+    adcValue += analogRead( ANALOG_SIGNAL_INPUT );
+    counts++;
+  } 
+  adcValue = adcValue / counts;
+
+  tft.fillScreen(LTDC_BLACK);
+  
+  tft.setCursor(0, 0);  
+  tft.setTextColor(LTDC_BLUE);
+  tft.setTextSize(2);
+  tft.println("analog input PA0");
+  tft.println("(blue button)");
+  
+  tft.setTextColor(LTDC_GREEN);
+  tft.setTextSize(3);
+  tft.print("adc val:"); tft.println( (int) adcValue);
+
+  tft.setCursor(20, 150);
+  tft.setTextColor(LTDC_YELLOW); 
+  tft.setTextSize(5);
+  float voltage = adcValue / 1024 * 3.3;
+  tft.print( voltage, 3 ); // print 3 post decimal positions
+  tft.print(" V");
+}
+