[SOLVED] How to correctly use millis() for delay

[PerryBebbington]

@ardumasterpro44

void loop() {
  char msg[] = "Hello!";                                                                                                 // Message
  for (uint8_t i = 0; i < rows; i++) {                                                                                   // Loop for every X-Axis bits
    if (millis() - time >= analogRead(pot) * (delayTime / 1023)) {                                                     // Wait for precision delay
      shiftByte(Data1, Data2, Clock1, Clock2, Latch, MSBFIRST, LSBFIRST, i, stringToChar(msg, i, rows), rows, columns);  // Shift the byte to the matrix
      time = millis();                                                                                                   // Store the time for precision delay
    }
  }
}

Your for loop and timer are backwards to each other. The timer should trigger the for loop once per delayTime, not have the for loop run every time through loop then do the timer. Swap the over so the for loop is inside the timer.