Program can produce a noise

Projects Programming
1

Just to let you to know. The program can produce a noise itself, the first Plott is AC voltmeter only, on second is added sine wave generator, input of AC voltmeter is connected to ground.

prograqm noise
prograqm noise1040×806 62.6 KB

2

What program?
Is there a question here?

3

Obviously yes.
That's why you always have to read the documentation of the micro you use, to avoid this type of surprises.

Regards

4

I've been wondering about that ringing in my ears.

1 Like
5

… answer the door then.

1 Like
6

A program can also produce music! In 1965, you could put a portable AM radio on top of an IBM 1440 computer and run a specific program and the radio would play Waltzing Matilda.

1 Like
7

This program, no question just statement, very often people have a problem with noise ......
The strange is that PA4 is on the ground and noise still present.


#include <LiquidCrystal.h>
#include "EmonLib.h"
LiquidCrystal lcd(PA0, PA1, PA2, PA3, PA4, PA5);

#define SAMPLES 102

#define DEBOUNCE_DELAY 100

#define DEBOUNCE_IDLE 0
#define DEBOUNCE_ACTIVE 1

#include <libmaple/dma.h>
#include <EEPROM.h>

double Voltage = 0;

struct debounce_info
{
  int start, state;
  int16 shift;
} left, right, up, down;

dma_tube_config dma_cfg, dma_cfg2;

int flag1 = 0;
int flag2 = 0;

int out1 = PB7;


int val1[SAMPLES];


int16 shift = 0;

int amp = 35;
int cnt = 0;
int time_track = 0;
float stp = 6.2831 / SAMPLES;
int ret = 17;

timer_dev *dev1 = PIN_MAP[out1].timer_device;

uint8 cc_channel1 = PIN_MAP[out1].timer_channel;


void fun()
{
  flag1++;
}

void fun2()
{
  flag2++;
}

void timer_conf()
{

  timer_dma_set_base_addr(dev1, TIMER_DMA_BASE_CCR2);
  timer_dma_set_burst_len(dev1, 1);
  timer_dma_enable_req(dev1, cc_channel1);
  timer_set_reload(dev1, 102);
  timer_set_prescaler(dev1, 0);

}

void dma_conf()
{
  dma_init(DMA1);
  /* T4C2 DMA C4 */
  dma_cfg.tube_dst = &(dev1->regs.gen->DMAR);
  dma_cfg.tube_dst_size = DMA_SIZE_32BITS;
  dma_cfg.tube_src = val1;
  dma_cfg.tube_src_size = DMA_SIZE_32BITS;

  dma_cfg.tube_nr_xfers = SAMPLES;
  dma_cfg.tube_flags = DMA_CFG_SRC_INC | DMA_CFG_CIRC | DMA_CFG_CMPLT_IE;

  dma_cfg.tube_req_src = DMA_REQ_SRC_TIM4_CH2;
  dma_cfg.target_data = 0;

  ret = dma_tube_cfg(DMA1, DMA_CH4, &dma_cfg);

  /* T1C1 DMA C2 */

  dma_cfg.tube_dst_size = DMA_SIZE_32BITS;
 
  dma_cfg.tube_src_size = DMA_SIZE_32BITS;

  dma_cfg.tube_nr_xfers = SAMPLES;
  dma_cfg.tube_flags = DMA_CFG_SRC_INC | DMA_CFG_CIRC | DMA_CFG_CMPLT_IE;

  dma_cfg.tube_req_src = DMA_REQ_SRC_TIM1_CH1;
  dma_cfg.target_data = 0;

  ret = dma_tube_cfg(DMA1, DMA_CH2, &dma_cfg);
}

void dma_start()
{
  dma_attach_interrupt(DMA1, DMA_CH4, fun);

  dma_enable(DMA1, DMA_CH4);
  timer_resume(dev1);

  dma_attach_interrupt(DMA1, DMA_CH2, fun2);

  dma_enable(DMA1, DMA_CH2);

}

void init_wave()
{
  int i;
  for (i = 0; i < SAMPLES; i++)
  {
    val1[i] = 50 + amp * sin(stp * i);

  }
}

void get_wave(int16 shift)
{
  int i;
  for (i = 0; i < SAMPLES; i++)
  {
  }
}

void setup() {
  int i;
  pinMode(out1, PWM);

 Serial.begin(115200);
  lcd.begin(16, 2);

  timer_conf();
  dma_conf();
  dma_start();

  init_wave();
  EEPROM.read(0, (uint16*)&shift);
  get_wave(shift);

}

void loop() {
   Voltage = getVPP();

  Serial.print(" Amps RMS = "); Serial.print( Voltage);
  Serial.println();

}


float getVPP()
{
  float result;
  int readValue;             //value read from the sensor
  int maxValue = 0;          // store max value here
  int minValue = 1024;          // store min value here, 4095.0
  //int minValue = 4095.0;

  uint32_t start_time = millis();
  while ((millis() - start_time) < 10)
    //while((millis()-start_time) < 100)  //sample for 1 Sec
  {

    readValue = analogRead(PA4);
    //readValue = analogRead(PB0);

    if (readValue > maxValue)
    {
      maxValue = readValue;
    }
    if (readValue < minValue)
    {
      minValue = readValue;
    }
  }
  result = (maxValue - minValue);

  return result;
}
8

I see that PA4 is connected to the display module. LCDs need an oscillator signal to allow
the segments to darken. Maybe that is what the noise is.

1 Like
9

So what you actually mean is that the program produces 'noise' not 'a noise', there is a big difference between those words. I am assuming you are not a native English speaker.

All digital electronic circuits produce noise. That is why we use, or should use, methods to remove this noise from a system. This is called decoupling and you can read about it here:-
http://www.thebox.myzen.co.uk/Tutorial/De-coupling.html

1 Like
10

I removed LCD = noise the same

11

Decoupling has nothing to do here, input is on ground.

12

I see what's puzzling you.
You are wondering why it isn't 0 if he input is grounded, correct?

13

A part of decoupling is to remove ground noise, sometimes called ground bounce. This can also be caused by poor ground layout, like you would get if you did not used a star ground wiring system.

14

yes

15

The difference between plots is only in the program.

16

Yes I know. It is a pity you can't understand me. Do you choose this misunderstanding or is it real?

17

I comment all lines with LCD and noise decreased by 50%

18

Yes, so what?

19

regardless of grounding, noise is also produced by the program itself.

20

Is this for an STM32 processor?