F429 disco ADC outliers

[ChrisMicro]

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The ADC functions randomly return 0 for several seconds.

[danieleff]

Can you put here a short test code for it?

[ChrisMicro]

It's a long time. I think it was this code: `

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

STM32F546 Discovery simple oscilloscope example

The oscilloscope has a auto trigger function to achieve a stable visual impression when a repeating signal like a sine wave is applied.

May 2017, ChrisMicro

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

#include "TFT_F429_Discovery.h"

TFT_F429_Discovery tft;

#define HORIZONTAL_RESOLUTION 240 #define VERTICAL_RESOLUTION 200 #define POSITION_OFFSET_Y 20 #define SIGNAL_LENGTH HORIZONTAL_RESOLUTION

uint16_t oldSignal[SIGNAL_LENGTH]; uint16_t adcBuffer[SIGNAL_LENGTH];

#define SAMPLING_TIME_US 20 #define ANALOG_SIGNAL_INPUT PC12

void setup() { tft.begin(); tft.fillScreen( LTDC_BLACK ); tft.fillRect(10, 1, 150, 160, LTDC_BLACK); //tft.setRotation(1); // horitzontal wide screen tft.setCursor(0, 0); tft.setTextColor(LTDC_GREEN); //tft.setTextSize(3); tft.setTextSize(2);

tft.println("analog input PC12"); tft.print("sampling frequency: "); tft.print(1000000 / SAMPLING_TIME_US); tft.println(" Hz");

// configure the ADC for 12 Bits analogReadResolution(12); }

void waitForAutoTrigger() {

uint32_t triggerLevel = 512; uint32_t hysteresis = 10; uint32_t timeOut_ms = 100;

uint32_t timeOutLimit = millis() + timeOut_ms; uint32_t timeOutFlag = false;

uint32_t adcValue = 0;

adcValue = analogRead( ANALOG_SIGNAL_INPUT );

// wait for low level while ( ( adcValue > triggerLevel - hysteresis ) && !timeOutFlag ) { adcValue = analogRead( ANALOG_SIGNAL_INPUT );

if ( millis() > timeOutLimit ) timeOutFlag = 1 ;

}

if ( !timeOutFlag ) { // wait for high level while ( ( adcValue < triggerLevel + hysteresis ) && ( millis() < timeOutLimit ) ) { adcValue = analogRead(ANALOG_SIGNAL_INPUT); } }

}

void showSignal() { int n;

int oldx; int oldy; int y;

for (n = 1; n < SIGNAL_LENGTH; n++) { y = VERTICAL_RESOLUTION - ( adcBuffer[n] * VERTICAL_RESOLUTION / 1024 ) + POSITION_OFFSET_Y;

if (n == 1)
{
  oldx = n;
  oldy = y;
}

if (n < SIGNAL_LENGTH - 1)
{
  // delete old line element
  tft.drawLine(n - 1 , oldSignal[n - 1], n, oldSignal[n], LTDC_BLACK );

  // draw new line element
  tft.drawLine(oldx,               oldy, n,            y, LTDC_GREEN );
}

oldSignal[n - 1] = oldy;
oldx = n;
oldy = y;

} }

void loop(void) { int n; uint32_t nextTime = 0;

//waitForAutoTrigger();

// record signal for (n = 1; n < SIGNAL_LENGTH; n++) { adcBuffer[n] = analogRead( ANALOG_SIGNAL_INPUT ); //adcBuffer[n] =random(0,200); // wait for next sample while (micros() < nextTime); nextTime = micros() + SAMPLING_TIME_US; }

showSignal(); delay(100); } `