esp8266 pixelflut server with a SSD1306 oled 128x64 screen

esp8266-ssd1306-i2c-pixelflut.ino

// esp8266 pixelflut server with a SSD1306 oled 128x64 screen
// only ascii PX x y RRGGBB\n supported for now, no SIZE or RRGGBBAA or binary protocol

#include <Wire.h>
#include "SSD1306Wire.h"
#include <ESP8266WiFi.h>
#include <WiFiUdp.h>

#define MAXBUF 4096

SSD1306Wire  display(0x3c, D3, D5);

WiFiUDP Udp;
unsigned int localUdpPort = 4242;
char incomingPacket[MAXBUF];
char replyPacket[] = "OK";

byte hexToByte (char c) {
  if ( (c >= '0') && (c <= '9') ) {
    return c - '0';
  }
  if ( (c >= 'A') && (c <= 'F') ) {
    return (c - 'A')+10;
  }
}

void setup() {
  int error;

  // setup network
  WiFi.begin("ssid", "password");

  display.init();
  display.flipScreenVertically(); // yeah lol, didnt even notice this in the test sketch when i breadboarded the screen
  display.setFont(ArialMT_Plain_10);

  while (WiFi.status() != WL_CONNECTED)
  {
    delay(100);
  }

  Udp.begin(localUdpPort);

  display.clear();
  display.setTextAlignment(TEXT_ALIGN_CENTER);
  display.drawString(64, 22, WiFi.localIP().toString());

  display.display();
  delay(4000);
  display.clear();
  display.display();


}

int pixels[128*64];

unsigned long previousMillis = 0;
const long interval = 50;

unsigned long timerstart = 0;

void loop() {
  unsigned long currentMillis = millis();

  // grab pixelflut ascii data
  // start by grabbing a packet from udp if any are there
  
  int packetSize = Udp.parsePacket();
  if (packetSize)
  {
    int len = Udp.read(incomingPacket, MAXBUF);
    if (len > 0)
    {
      incomingPacket[len] = '\0';
    }
  }

  // the buffer now has a packet (probably..) so lets parse it
  // format is "PX x y 24bithexcolor\n" and can come multiple times per package

  char *saveptr1, *saveptr2;
  char *token = strtok_r(incomingPacket, "\n", &saveptr1);
  while (token) {
    // token should be a single pixel now

    char *subtoken = strtok_r(token," ", &saveptr2);
    int pos = 0;
    int pixelvalues[8];
    byte n = 0;

    while (subtoken) {
      // iterate through space seperated 
      if (pos==3) {
        n = hexToByte( subtoken[ 0 ] );
        n = ( n * 16 ) + hexToByte( subtoken[1] );
        pixelvalues[2] = n;
        n = hexToByte( subtoken[ 2 ] );
        n = ( n * 16 ) + hexToByte( subtoken[3] );
        pixelvalues[3] = n;
        n = hexToByte( subtoken[ 4 ] );
        n = ( n * 16 ) + hexToByte( subtoken[5] );
        pixelvalues[4] = n;

      } else if (pos>0) {
        pixelvalues[pos-1] = atoi(subtoken);
      }
      pos++;
      // first time 'PX' , second time 'x' , third time 'y' , last time 'hex'
      // maybe an array?
      subtoken = strtok_r(NULL," ", &saveptr2);
    }

    token = strtok_r(NULL, "\n", &saveptr1);

    // some fancier methods are possible for picking a 0-255 value for a pixel, but i'm just grabbing G for now

    //pixels[(pixelvalues[1]*20)+pixelvalues[0]] = (pixelvalues[2]/3)+(pixelvalues[3]/2)+(pixelvalues[4]/6);
    //pixels[(pixelvalues[1]*20)+pixelvalues[0]] = (pixelvalues[2]+pixelvalues[3]+pixelvalues[4])/3;

    pixels[(pixelvalues[1]*128)+pixelvalues[0]] = pixelvalues[2];

  }

  // display
  display.clear();

  for (int x = 0; x < 128; x++ ) {
    for (int y = 0; y < 64; y+=2 ) {
      // either this pixel is on or off

      if (pixels[(y*128)+x]>127) {
        display.setPixel(x,y);
      } else {
        // dont have to do anything, cause we .clear()'ed the buffer
      }

    }
  }

  // oled isnt that fast, dont draw too often
  // actually not really needed but meh

  if (currentMillis - previousMillis >= interval) {
    previousMillis = currentMillis;
    display.display();

  }

}