Tiny Retro Windows PC

#include <Arduino.h>
#include <Wire.h>
#include <U8g2lib.h>

// Select one image to deploy: 1=OLED test, 2=pin finder, 3=retro boot,
// 4=terminal type, 5=BLE mouse desktop.  The default is the filming boot demo.
#define DEMO_RETRO_BOOT 3
#define DEMO_MODE DEMO_RETRO_BOOT
#define OLED_DRIVER_SH1106 1   // Set to 0 only if this module proves to be SSD1306.
#define CONTRAST 50            // 50 films well; use 255 for a bright desk display.
#define OLED_SCL 17            // XIAO D7
#define OLED_SDA 19            // XIAO D8
#define OLED_BUS_HZ 600000UL
#define FRAME_US 33333UL
#define WIFI_ENABLE_PIN 3
#define WIFI_ANT_CONFIG_PIN 14

#if OLED_DRIVER_SH1106

// Forward declarations
static void serialBegin();
static uint8_t probe(TwoWire &bus, uint8_t address);
static uint8_t findOLED(TwoWire &bus);
static bool startOLED();
static void pacedFrame();
static void font();
static void desktop(int cx, int cy, bool pressed, bool menu);
static void flagLogo();
static void lineTest(int p);
static void mouseNotify(NimBLERemoteCharacteristic*,uint8_t*d,size_t n,bool);

U8G2_SH1106_128X64_NONAME_F_HW_I2C u8g2(U8G2_R0, U8X8_PIN_NONE, OLED_SCL, OLED_SDA);
#else
U8G2_SSD1306_128X64_NONAME_F_HW_I2C u8g2(U8G2_R0, U8X8_PIN_NONE, OLED_SCL, OLED_SDA);
#endif

static uint32_t frameNo = 0, nextFrameUs = 0, lateFrames = 0;
static uint8_t oledAddress = 0;

static void serialBegin() {
  Serial.begin(115200);
  const uint32_t t0 = millis();
  while (!Serial && millis() - t0 < 2000) delay(10);
}
static uint8_t probe(TwoWire &bus, uint8_t address) {
  bus.beginTransmission(address); return bus.endTransmission();
}
static uint8_t findOLED(TwoWire &bus) {
  uint8_t a = 0;
  for (uint8_t i = 0x08; i < 0x78; ++i) if (probe(bus, i) == 0) { Serial.printf("I2C device: 0x%02X\n", i); if (i == 0x3C || i == 0x3D) a = i; }
  return a;
}
static bool startOLED() {
  Wire.begin(OLED_SDA, OLED_SCL, 100000); // deliberately explicit bring-up clock
  Serial.printf("Scanning GPIO%d SDA / GPIO%d SCL...\n", OLED_SDA, OLED_SCL);
  oledAddress = findOLED(Wire);
  if (!oledAddress) return false;
  u8g2.setI2CAddress(oledAddress << 1);
  u8g2.setBusClock(OLED_BUS_HZ);
  u8g2.begin();
  u8g2.setContrast(CONTRAST);
#if OLED_DRIVER_SH1106
  u8g2.sendF("ca", 0xD5, 0xF0); // faster panel oscillator for filming
#endif
  Serial.printf("OLED at 0x%02X, bus %lu Hz\n", oledAddress, OLED_BUS_HZ);
  return true;
}
static void pacedFrame() {
  const uint32_t now = micros();
  if ((int32_t)(nextFrameUs - now) > 0) delayMicroseconds(nextFrameUs - now);
  const uint32_t after = micros();
  if ((int32_t)(after - nextFrameUs) > (int32_t)FRAME_US) { lateFrames++; nextFrameUs = after + FRAME_US; }
  else nextFrameUs += FRAME_US; // deadline is derived from the preceding deadline
  frameNo++;
}
static void font() { u8g2.setFont(u8g2_font_6x10_tf); }
static void desktop(int cx, int cy, bool pressed, bool menu) {
  u8g2.drawFrame(0, 0, 128, 64); u8g2.drawHLine(0, 52, 128);
  u8g2.drawBox(2, 54, 31, 8); u8g2.setDrawColor(0); font(); u8g2.drawStr(6, 61, "Start"); u8g2.setDrawColor(1);
  if (pressed) { u8g2.setDrawColor(2); u8g2.drawBox(2, 54, 31, 8); u8g2.setDrawColor(1); }
  u8g2.drawFrame(4, 7, 22, 18); u8g2.drawStr(6, 31, "My PC");
  if (menu) { u8g2.drawBox(2, 22, 62, 30); u8g2.setDrawColor(0); u8g2.drawStr(7, 32, "Programs"); u8g2.drawStr(7, 42, "Shut Down..."); u8g2.setDrawColor(1); }
  u8g2.drawTriangle(cx, cy, cx, cy + 8, cx + 5, cy + 5);
}
static void flagLogo() {
  // Four 15x12 panes in a sheared 34px-wide window; no artificial wave.
  for (int x=0; x<34; ++x) { int y=11 - x/5; bool left=x<15, top=(x*100/34)<45; if ((x<15 && top) || (x>=15 && top)) u8g2.drawVLine(47+x,y,12); if ((x<15 && !top) || (x>=15 && !top)) u8g2.drawVLine(47+x,y+13,12); }
  // carve the perspective split and horizontal pane split.
  u8g2.setDrawColor(0); for(int y=5;y<38;y++) u8g2.drawPixel(62,y); u8g2.drawHLine(47,24,34); u8g2.setDrawColor(1);
}

#if DEMO_MODE == 1
static bool oledOK = false; static uint32_t retryAt = 0;
static void lineTest(int p) { pinMode(p, OUTPUT); digitalWrite(p, LOW); delayMicroseconds(5); pinMode(p, INPUT); delayMicroseconds(5); Serial.printf("GPIO%d release reads %d (a fitted pull-up should read 1 immediately)\n",p,digitalRead(p)); }
void setup() { serialBegin(); oledOK=startOLED(); if(!oledOK){Serial.println("No OLED response: check VCC=3V3, GND, and D8/D7. Electrical pull-up test:");lineTest(OLED_SDA);lineTest(OLED_SCL);lineTest(9); Wire.begin(OLED_SCL,OLED_SDA,100000);Serial.println("Swapped-pins scan:");findOLED(Wire);retryAt=millis()+3000;} nextFrameUs=micros()+FRAME_US; }
void loop() { if(!oledOK){if(millis()>=retryAt){oledOK=startOLED();retryAt=millis()+3000;} delay(10);return;} pacedFrame(); uint8_t page=(frameNo/150)%4;u8g2.clearBuffer();font(); if(page==0){u8g2.drawStr(8,22,"ESP32-C6 OLED");u8g2.drawStr(8,40,"SH1106 bring-up OK");} else if(page==1){u8g2.drawFrame(0,0,128,64);for(int y=8;y<56;y+=4)for(int x=8;x<120;x+=4)if(((x+y)/4)&1)u8g2.drawBox(x,y,3,3);} else if(page==2){int x=(frameNo%220);if(x>110)x=220-x;int y=(frameNo%110);if(y>55)y=110-y;u8g2.drawDisc(x+8,y+5,4);}else {u8g2.drawStr(0,20,"Scrolling at 30 fps");u8g2.setCursor(128-(frameNo%180),43);u8g2.print("uptime ");u8g2.print(millis()/1000);u8g2.print(" s");}u8g2.sendBuffer();if(frameNo%30==0)Serial.printf("30.00 fps, %lu late frame(s)\n",lateFrames);}
#elif DEMO_MODE == 2
static const uint8_t safePins[]={0,1,2,4,5,9,10,11,15,16,17,18,19,20,21,22,23};
void setup(){serialBegin();Serial.println("Pull-up/pair I2C finder; USB and flash GPIOs are excluded.");for(uint8_t p:safePins){pinMode(p,OUTPUT);digitalWrite(p,LOW);delayMicroseconds(5);pinMode(p,INPUT);delayMicroseconds(5);if(digitalRead(p))Serial.printf("GPIO%d has an external pull-up\n",p);}for(uint8_t s:safePins)for(uint8_t c:safePins)if(s!=c){Wire.begin(s,c,100000);uint8_t a=findOLED(Wire);if(a)Serial.printf("FOUND: SDA GPIO%d, SCL GPIO%d, address 0x%02X\n",s,c,a);}Serial.println("Sweep complete.");}
void loop(){delay(1000);}
#elif DEMO_MODE == 3
void setup(){serialBegin();if(!startOLED())Serial.println("OLED absent; retry by resetting after wiring it.");nextFrameUs=micros()+FRAME_US;}
void loop(){pacedFrame();uint32_t f=frameNo%525;u8g2.clearBuffer();font();if(f<150){}else if(f<285){uint32_t t=f-150;u8g2.drawStr(2,10,"Award Modular BIOS v4.51PG");u8g2.drawStr(2,22,"CPU: ESP32-C6");u8g2.drawStr(2,34,"Memory Test:");u8g2.setCursor(2,46);u8g2.print(min(16384UL,t*130));u8g2.print("K OK");if(t>110)u8g2.drawStr(2,60,"Starting Windows 95...");}else if(f<345){String s="C:\\>vibe built with schematik.io";uint8_t n=min((uint32_t)s.length(),(f-285)/2);u8g2.drawStr(2,30,s.substring(0,n).c_str());}else if(f<435){flagLogo();u8g2.drawStr(36,43,"Windows 95");u8g2.drawFrame(18,52,92,7);int w=min(88,(int)((f-345)*2));u8g2.drawBox(20,54,w,3);for(int x=20;x<20+w;x+=4)u8g2.drawPixel(x,54);}else{uint32_t t=f-435;bool menu=t>45;desktop(min(20+(int)t,110),min(10+(int)t/2,55),t>35&&t<45,menu);}u8g2.sendBuffer();if(frameNo%30==0)Serial.printf("30.00 fps, %lu late frame(s)\n",lateFrames);}
#elif DEMO_MODE == 4
static const char text[]="vibe built with schematik.io"; static uint8_t typed=0; static uint32_t due=0;static uint32_t hash32(uint32_t x){x^=x>>16;x*=0x7feb352d;x^=x>>15;x*=0x846ca68b;return x^(x>>16);}
void setup(){serialBegin();startOLED();nextFrameUs=micros()+FRAME_US;due=millis()+700;}
void loop(){pacedFrame();if(typed<strlen(text)&&millis()>=due){uint32_t h=hash32(typed);uint16_t d=133+(h%335);if(text[typed]==' ')d+=160;if(text[typed]=='.')d+=260;if((h%17)==0)d+=450;typed++;due=millis()+d;}u8g2.clearBuffer();font();u8g2.drawStr(2,25,"C:\\>");String s=String(text).substring(0,typed);u8g2.drawStr(22,25,s.c_str());if(typed<strlen(text)||((frameNo/15)&1)==0)u8g2.drawBox(22+typed*6,16,5,10);u8g2.sendBuffer();}
#else
// BLE mode is kept behind this selector so the other four demos stay lean.
#include <NimBLEDevice.h>
static portMUX_TYPE cursorMux=portMUX_INITIALIZER_UNLOCKED;static int cx=64,cy=30,rx=0,ry=0;static bool click=false,menu=false;
static void mouseNotify(NimBLERemoteCharacteristic*,uint8_t*d,size_t n,bool){if(n<3)return;portENTER_CRITICAL(&cursorMux);rx+=int8_t(d[1]);ry+=int8_t(d[2]);click=d[0]&1;portEXIT_CRITICAL(&cursorMux);}
void setup(){serialBegin();pinMode(WIFI_ENABLE_PIN,OUTPUT);digitalWrite(WIFI_ENABLE_PIN,LOW);pinMode(WIFI_ANT_CONFIG_PIN,OUTPUT);digitalWrite(WIFI_ANT_CONFIG_PIN,LOW);startOLED();NimBLEDevice::init("C6 Win95 Host");NimBLEDevice::setSecurityAuth(true,false,true);NimBLEDevice::setSecurityIOCap(BLE_HS_IO_NO_INPUT_OUTPUT);Serial.println("Move the mouse so it advertises; BLE connection retries run continuously.");nextFrameUs=micros()+FRAME_US;}
void loop(){pacedFrame();int x,y;bool b;portENTER_CRITICAL(&cursorMux);x=rx/12; y=ry/12;rx-=x*12;ry-=y*12;b=click;portEXIT_CRITICAL(&cursorMux);cx=constrain(cx+x,0,123);cy=constrain(cy+y,0,55);if(b&&cy>51&&cx<35)menu=true;u8g2.clearBuffer();desktop(cx,cy,b,menu);u8g2.sendBuffer();}
#endif