ESP32 E-Paper Display Interface

#include <Arduino.h>
#include <WiFi.h>
#include <time.h>
#include <WebServer.h>

#include <GxEPD2_3C.h>
#include <SPI.h>
#include <Adafruit_SSD1306.h>
Adafruit_SSD1306 oled(128,64,13,14,22,21,32);
bool oledReady=false;
String oledView;
#include "config.h"
#include "dashboard.h"
#include "picture1.h"
#include "picture2.h"
#include "picture3.h"
#include "picture4.h"
GxEPD2_3C<GxEPD2_213_Z98c, GxEPD2_213_Z98c::HEIGHT> screen(GxEPD2_213_Z98c(27,26,25,33));
String lastView;
WebServer server(80);
String pendingApp="ANDROID READY", pendingTitle="Send a notification", pendingBody;
bool pending=true, hadNotification=false;
uint32_t lastRefresh=0, lastReceived=0;
void receiveNotification(){
 if(server.header("Authorization") != String("Bearer ")+BRIDGE_TOKEN){server.send(401,"text/plain","Unauthorized");return;}
 String payload=server.arg("plain");
 if(payload.length()>2048){server.send(413,"text/plain","Too long");return;}
 int first=payload.indexOf('\n'), second=payload.indexOf('\n',first+1);
 if(first<1 || second<0){server.send(400,"text/plain","Use app, title, body on separate lines");return;}
 pendingApp=payload.substring(0,first); pendingTitle=payload.substring(first+1,second); pendingBody=payload.substring(second+1);
 lastReceived=millis(); hadNotification=true; pending=true;
 server.send(202,"text/plain","Notification queued");
}
uint32_t lastWifiAttempt=0;
int lastWifiStatus=-1;
String clean(String s) {
 for(size_t i=0;i<s.length();i++) if((uint8_t)s[i]<32 || (uint8_t)s[i]>126) s.setCharAt(i,' ');
 return s;
}
const uint16_t* pictures[]={PICTURE1_DATA,PICTURE2_DATA,PICTURE3_DATA,PICTURE4_DATA};
uint8_t pictureIndex=0;
uint32_t pictureSince=0;
void drawPicture(int height){
 const uint16_t* data=pictures[pictureIndex];
 // Trim black padding and center-crop to fill the entire artwork area.
 int top=250,bottom=-1,leftEdge=122,rightEdge=-1;
 for(int y=0;y<250;y++) for(int x=0;x<122;x++)
  if(pgm_read_word(data+y*122+x)!=0){
   top=min(top,y);bottom=max(bottom,y);
   leftEdge=min(leftEdge,x);rightEdge=max(rightEdge,x);
  }
 if(bottom<top){top=0;bottom=249;leftEdge=0;rightEdge=121;}
 int sourceW=rightEdge-leftEdge+1,sourceH=bottom-top+1;
 float scale=max(122.0f/sourceW,float(height)/sourceH);
 int width=max(1,int(sourceW*scale)),drawH=max(1,int(sourceH*scale));
 int offsetX=(122-width)/2,offsetY=(height-drawH)/2;
 for(int y=0;y<drawH;y++) for(int x=0;x<width;x++){
  int sx=constrain(leftEdge+int(x/scale),leftEdge,rightEdge);
  int sy=constrain(top+int(y/scale),top,bottom);
  uint16_t c=pgm_read_word(data+sy*122+sx);
  int r=((c>>11)&31)*255/31,g=((c>>5)&63)*255/63,b=(c&31)*255/31;
  // Ordered halftoning preserves grey details using real black/white pixels.
  // Keep saturated warm highlights red; lift neutral details for this panel.
  static const uint8_t bayer[4][4]={{0,8,2,10},{12,4,14,6},{3,11,1,9},{15,7,13,5}};
  int luminance=(r*54+g*183+b*19)/256;
  int threshold=48+bayer[y&3][x&3]*11;
  bool red=(r>70 && r>g*1.4 && r>b*1.25);
  uint16_t ink=red?GxEPD_RED:(luminance>threshold?GxEPD_WHITE:GxEPD_BLACK);
  if(offsetX+x>=0 && offsetX+x<122 && offsetY+y>=0 && offsetY+y<height)
   screen.drawPixel(offsetX+x,offsetY+y,ink);
 }
}
void updateOled(){
 if(!oledReady)return;
 time_t now=time(nullptr);
 struct tm t;
 char clockText[24]="--:-- UTC",dateText[24]="Waiting for time",weekText[24]="";
 if(now>1700000000 && gmtime_r(&now,&t)){
  strftime(clockText,sizeof(clockText),"%H:%M UTC",&t);
  strftime(dateText,sizeof(dateText),"%d %b %Y",&t);
  strftime(weekText,sizeof(weekText),"%a  Week %V",&t);
 }
 String status=WiFi.status()==WL_CONNECTED?"ONLINE":"OFFLINE";
 String app=clean(pendingApp).substring(0,21);
 String title=clean(pendingTitle).substring(0,21);
 String body=clean(pendingBody).substring(0,42);
 String key=String(clockText)+dateText+weekText+status+app+title+body;
 if(key==oledView)return;
 oled.clearDisplay();oled.setTextSize(1);oled.setTextColor(SSD1306_WHITE);
 oled.setTextWrap(false);
 oled.setCursor(0,0);oled.print(clockText);
 oled.setCursor(86,0);oled.print(status);
 oled.setCursor(0,8);oled.print(dateText);
 oled.setCursor(0,16);oled.print(weekText);
 oled.setCursor(0,24);oled.print(app);
 oled.setCursor(0,32);oled.print(title);
 oled.setCursor(0,40);oled.print(body.substring(0,21));
 oled.setCursor(0,48);oled.print(body.substring(21,42));
 oled.setCursor(0,56);
 if(WiFi.status()==WL_CONNECTED)oled.print(WiFi.localIP());
 else oled.print("Reconnecting Wi-Fi...");
 oled.display();oledView=key;
}
void showWallpaper(){
 String key=String(pictureIndex);
 if(key==lastView)return;
 screen.init(115200,true,2,false);
 screen.setRotation(0);screen.setFullWindow();screen.firstPage();
 do{
  screen.fillScreen(GxEPD_BLACK);
  drawPicture(250);
 }while(screen.nextPage());
 screen.hibernate();lastView=key;
}
void setup(){
 Serial.begin(115200);
 pinMode(27,OUTPUT);digitalWrite(27,HIGH);
 pinMode(26,OUTPUT);pinMode(25,OUTPUT);digitalWrite(25,HIGH);
 SPI.begin(18,-1,23,27);
 oledReady=oled.begin(SSD1306_SWITCHCAPVCC);
 if(!oledReady) Serial.println("OLED buffer allocation failed");
 WiFi.mode(WIFI_STA); WiFi.setAutoReconnect(true);
 WiFi.begin(WIFI_SSID,WIFI_PASSWORD);
 configTime(0,0,"pool.ntp.org","time.nist.gov");
 const char* headers[]={"Authorization"};
 server.collectHeaders(headers,1);
 server.on("/notify",HTTP_POST,receiveNotification);
 server.on("/",HTTP_GET,[]{server.sendHeader("Cache-Control","no-store");server.send_P(200,"text/html",DASHBOARD_HTML);});
 server.begin();
 lastWifiAttempt=millis();
 Serial.printf("Connecting to Wi-Fi: %s\n", WIFI_SSID);
 updateOled();
 showWallpaper();
 pictureSince=millis();
}
void loop(){
 int status=WiFi.status();
 if(status!=lastWifiStatus){
  Serial.printf("Wi-Fi status: %d (3=connected, 1=network not found, 4=connection failed, 6=disconnected)\n",status);
  if(status==WL_CONNECTED) Serial.printf("Wi-Fi connected. IP: %s\n",WiFi.localIP().toString().c_str());
  lastWifiStatus=status;
 }
 if(status!=WL_CONNECTED){
  if(millis()-lastWifiAttempt>=30000){WiFi.reconnect();lastWifiAttempt=millis();}
 }else server.handleClient();
 if(!hadNotification && pending) pendingBody="IP: "+WiFi.localIP().toString();
 // Notifications never refresh the e-paper; the OLED retains the latest one.
 pending=false;
 updateOled();
 if(millis()-pictureSince>=60000){
  pictureIndex=(pictureIndex+1)%4;
  showWallpaper();
  pictureSince=millis();
 }
 delay(20);
}