7-Segment-Display stuttering when showing sensor output due to delays

Other Hardware LEDs and Multiplexing
1

Hello,

I built a simple distance sensor box for a bigger project. It measures distance with an ultrasonic sensor and sends it to another Arduino via RF. All of that works fine, however I thought it would be neat to have the measured distance output to a 7-segment-display so I connected that too. Due to the nature of SevSeg.h's refreshDisplay(), I can't use any delays in the main loop, however my sensor does need delays to properly measure the distance. Is there a way to get the seven segment display to display the measured distance properly? Right now it flickers once I activate all the delays and works fine when they're off, however the sensor stops working.

Here is my code: http://pastebin.com/Y6fB43C6

Thank you in forward!

2

Please post your code here - don't forget the code tags

3

Sure thing, here it is:

#include <VirtualWire.h>
#include <SevSeg.h>

#define trigPin A0
#define echoPin A1

//RF-Transmitter
char Sensor1CharMsg[4];
long distance;

static unsigned long timer = millis();

void setup() {
  Serial.begin(9600);      // open the serial port at 9600 bps:

  byte numDigits = 4;
  byte digitPins[] = {2, 3, 4, 5};
  byte segmentPins[] = {6, 7, 8, 9, 10, 11, 12, 13};
  bool resistorsOnSegments = false;
  byte hardwareConfig = COMMON_CATHODE;
  sevseg.begin(hardwareConfig, numDigits, digitPins, segmentPins, resistorsOnSegments);
  sevseg.setBrightness(80);

  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);

  vw_set_ptt_inverted(false);
  vw_set_tx_pin(A2);
  vw_setup(4000); // speed of data transfer Kbps
}

void loop() {

  if (millis() >= timer) {
    if (distance >= 200 || distance <= 0) {
      sevseg.setNumber(0);
    } else {
      sevseg.setNumber(distance);
    }
	sevseg.refreshDisplay();
    timer += 250;
  } else {
    long duration;
    digitalWrite(trigPin, LOW);
    delayMicroseconds(2);
    digitalWrite(trigPin, HIGH);
    delayMicroseconds(10);
    digitalWrite(trigPin, LOW);
    duration = pulseIn(echoPin, HIGH);
    distance = (duration / 2) / 29.1;

    itoa(distance, Sensor1CharMsg, 10);
    vw_send((uint8_t *)Sensor1CharMsg, strlen(Sensor1CharMsg));
    vw_wait_tx(); // Wait until the whole message is gone
  }
}
4

It's hard to believe that 12 microseconds of delays (two microseconds of which are unnecessary) is causing your problem - more likely "pulseIn".
Try the NewPing library.

5

Thanks for the suggestion, NewPing looks much more elegant than my solution. I've implemented it but the refresh rate is still too low for refreshDisplay(). I commented out line for line and it seems that just the vw_send command is enough to have it flicker too much to make out any numbers.