UNO, one 74HC595 and four 8-segment displays, just querying

Other Hardware LEDs and Multiplexing
1

Just a general query as got it all running although I expect my coding could be better. It all runs and flickers but I am assuming that is from the switching and can it be got rid off, or am I stuck with it?

I could use 3 more 74HC595 but was just seeing if I could get it working without. So really just after some feedback. Here is my code. I have 2 timing values one for overall, and one for switching between the 8-segment displays. Am only starting out so go easy :slight_smile:

const int SER     = 8;
const int LATCH   = 9;
const int CLK     =10;
const int LED1    =2; //on off for 7-segment one
const int LED2    =3; //on off for 7-segment two
const int LED3    =4; //on off for 7-segment three
const int LED4    =5; //on off for 7-segment four



int interval = 200; //how many millis to cycle between numbers 
int interval2 = 11; //delay between switching between 7-segment displays

int firstdigit = 0; //integers to hold individual digit values
int seconddigit = 0;
int thirddigit = 0;
int fourthdigit = 0;

//sequence of 0-10
int sequence[10] = {63,6,91,79,102,109,124,7,127,111}; //numbers 0-9 for segment

void showvalues(int one,int two, int three, int four) //function to display values
{
  unsigned long currentmillis = millis(); //store current millis
  do
  {
    digitalWrite(LATCH, LOW);
    shiftOut(SER, CLK, MSBFIRST, sequence[one]);
    digitalWrite(LATCH, HIGH);
    digitalWrite (LED1, HIGH);
    delay(interval2);
    digitalWrite (LED1, LOW);
    
    digitalWrite(LATCH, LOW);
    shiftOut(SER, CLK, MSBFIRST, sequence[two]);
    digitalWrite(LATCH, HIGH);
    digitalWrite (LED2, HIGH);
    delay(interval2);
    digitalWrite (LED2, LOW);
    
    digitalWrite(LATCH, LOW);
    shiftOut(SER, CLK, MSBFIRST, sequence[three]);
    digitalWrite(LATCH, HIGH);
    digitalWrite (LED3, HIGH);
    delay(interval2);
    digitalWrite (LED3, LOW);
    
    digitalWrite(LATCH, LOW);
    shiftOut(SER, CLK, MSBFIRST, sequence[four]);
    digitalWrite(LATCH, HIGH);
    digitalWrite (LED4, HIGH);
    delay(interval2);
    digitalWrite (LED4, LOW);
    
    Serial.print(one);
    Serial.print("  ");
    Serial.print(two);
    Serial.print("  ");
    Serial.print(three);
    Serial.print("  ");
    Serial.print(four);
    Serial.print("  currentmillis: ");
    Serial.print(currentmillis);
    Serial.print(" actual millis: ");
    Serial.println(millis());
    
    unsigned long int x = millis() - currentmillis;
    
  } while ((millis()-currentmillis) < interval);
}

void setup()
{
  Serial.begin(9600); //start serial
  
  pinMode(SER, OUTPUT);
  pinMode(LATCH, OUTPUT);
  pinMode(CLK, OUTPUT);
  pinMode(LED1, OUTPUT);
  pinMode(LED2, OUTPUT);
  pinMode(LED3, OUTPUT);
  pinMode(LED4, OUTPUT);
}

void loop()
{
  for (int i = 0; i < 9999; i++)
  {
    int b = i;
    firstdigit = b % 10;
    b = b/10;
    seconddigit = b % 10;
    b=b/10;
    thirddigit = b % 10;
    b=b/10;
    fourthdigit = b % 10;
    showvalues(firstdigit, seconddigit, thirddigit, fourthdigit);
  }
}

WP_20140622_001[1].jpg

2

Does the flickering improve if you speed up the serial speed, try 115200, or comment out all the serial prints?

3

Many thanks, at first neither worked. But then remembered that I had tried using delaymicroseconds instead of delay (didn't work). But with the serial print commented out I tried tweaking the timing for interval2 (timing between switching the segment displays)again. This resulted in a nice display when set at 5 or below.

Have also moved the serial print lines in to the actual void loop () and display is still good. I should of considered the impact of the serial printing embedded in the function especially if cycling so fast.

Many thanks again for the pointer and help.

4

Glad to help.