Seven segment and arduino

Interesting application. I thought you might be doing a test instrument, or something like that.

I had imagined it was a traditional scan, where you'd scan the anodes in turn and present the segment drive (in a 1:4 multiplex). If the brightness remains constant, you must be scanning the segments in turn and deciding whether or not to drive the anode (an 1:8 multiplex).

I don't see that a Charlieplex helps. With the anodes connected, there's no possibility of having diodes back-to-back nor of maximising the connection possibilities between the IO pins, which is where the savings come from.

I don't have much experience with Arduino programming. Can't you set up a timer to generate an interrupt at regular intervals and use the interrupt routine to drive the display? That way it would be a backgound process and you could do what you like with the rest of your code without it having an impact on the scanning.

Hi

Im actually use it to display text on a remote vehicle.

The sevseg lib can do text also...

Actually the brightness can be adjusted. I will paste my code at the buttom.

You can also adjust the brightness using which resistors values you put in the circuit. Here i have 1k. When i tried 100ohm it was too bright.

Thanks allot for the i2c extender that what exactly what i wanted.

Also do you have a clue if i could use charlie plexing? This will decrese mips from the arduino and remove blinking from the display.

This is my code for now.

I just changed the pins which i used. And the brightness.

/* SevSeg Counter Example

 Copyright 2017 Dean Reading

 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
 You may obtain a copy of the License at 
 http://www.apache.org/licenses/LICENSE-2.0

 Unless required by applicable law or agreed to in writing, software
 distributed under the License is distributed on an "AS IS" BASIS,
 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.


 This example demonstrates a very simple use of the SevSeg library with a 4
 digit display. It displays a counter that counts up, showing deci-seconds.
 */


#include "SevSeg.h"
SevSeg sevseg; //Instantiate a seven segment controller object


void setup() {
  byte numDigits = 4;
  byte digitPins[] = {5, 4, 3, 2};
  byte segmentPins[] = {12, 11, 10, 9, 8, 7, 6, 13};
  bool resistorsOnSegments = false; // 'false' means resistors are on digit pins
  byte hardwareConfig = COMMON_ANODE; // See README.md for options
  bool updateWithDelays = false; // Default. Recommended
  bool leadingZeros = false; // Use 'true' if you'd like to keep the leading zeros
  
  sevseg.begin(hardwareConfig, numDigits, digitPins, segmentPins, resistorsOnSegments, updateWithDelays, leadingZeros);
  sevseg.setBrightness(10);
}


void loop() {
  static unsigned long timer = millis();
  static int deciSeconds = 0;
  
  if (millis() >= timer) {
    deciSeconds++; // 100 milliSeconds is equal to 1 deciSecond
    timer += 100; 
    if (deciSeconds == 10000) { // Reset to 0 after counting for 1000 seconds.
      deciSeconds=0;
    }
    sevseg.setNumber(deciSeconds, 1);
  }


  sevseg.refreshDisplay(); // Must run repeatedly
}


/// END ///

This is a whole solution for i2c but in a pretty high price.

I am looking on a i2c adapter only.

And that the arduino will actually can have extended io with it.

Good to see you experimenting and working things out for yourself. What are you going to show on the display?

If you just use the four resistors, doesn't the brightness change depending on how many segments are on?

You could try an I2C expander like this if you want an I2C connection:

http://uk.farnell.com/microchip/mcp23017-e-sp/ic-io-expander-16bit-i2c-28dip/dp/1332088

There's a whole range of them. I think you can get similar parts for SPI, too.

Alternatively, you could use a microcontroller acting as an I2C slave. Advantage of that is the uC could do the scanning and the Arduino would only need to send data as and when it changed.

MAX7219 or something like this?