Код:

#define PIN_DATA 11 // D- chip WHITE
#define PIN_CLOCK 10 // D+ chip GREEN 
#define PIN_CHIP_VCC A5 // 0=on 1=off
#define PIN_USB_CONNECT 2 // relay
#define PIN_PU 3 // external pull up
#define PIN_SW A0 // switch 1=NORMAL_MODE 0=BOOT_MODE
#define PIN_LED_R 5 // BOOT_MODE
#define PIN_LED_G 4 // NORMAL_MODE

#define BOOT_MODE 1
#define NORMAL_MODE 0

uint8_t mode = 255;
uint8_t boot_mode_ok=0;

void send_key()
{
  for(int8_t i = 15; i >= 0; i--)
  {    
    delayMicroseconds(15);
    digitalWrite(PIN_DATA, 0x16EF >> i & 0x1);
    digitalWrite(PIN_CLOCK, 0);
    delayMicroseconds(15);
    digitalWrite(PIN_CLOCK, 1);  
  }
}

void setup()
{  
  pinMode(PIN_LED_G, OUTPUT);
  pinMode(PIN_LED_R, OUTPUT);
  pinMode(PIN_CHIP_VCC, OUTPUT);
  pinMode(PIN_USB_CONNECT, OUTPUT);  
  pinMode(PIN_SW, INPUT_PULLUP);
  pinMode(PIN_CLOCK, INPUT);
  pinMode(PIN_DATA, INPUT);
  pinMode(PIN_PU, INPUT); 

  digitalWrite(PIN_LED_G, 0);
  digitalWrite(PIN_LED_R, 0);
  digitalWrite(PIN_CHIP_VCC, 1);
  digitalWrite(PIN_USB_CONNECT, 0);

  if(digitalRead(PIN_SW))   
    go_normal_mode();
  else  
    go_boot_mode();  
}

void go_boot_mode()
{
  if(mode != BOOT_MODE)
  {
    mode = BOOT_MODE;
    digitalWrite(PIN_LED_G, 0); // normal mode off
    digitalWrite(PIN_USB_CONNECT, 0); // disconnect usb
    digitalWrite(PIN_CHIP_VCC, 1); // chip power off    
    delay(1000);// discharge c on chip VCC
    digitalWrite(PIN_CHIP_VCC, 0); // chip power on
    delay(10); // wait for chip ready
    while(!boot_mode_ok)
    {
      pinMode(PIN_CLOCK, OUTPUT);
      pinMode(PIN_DATA, OUTPUT);
      send_key();   
      pinMode(PIN_CLOCK, INPUT);
      pinMode(PIN_DATA, INPUT);
      pinMode(PIN_PU, OUTPUT);
      digitalWrite(PIN_PU, 1); // external pull_up on
      if(!digitalRead(PIN_DATA))
      {      
        boot_mode_ok=1; // D- pulled down        
        pinMode(PIN_PU, INPUT);  // external pull_up off 
        digitalWrite(PIN_USB_CONNECT, 1); // connect usb
        digitalWrite(PIN_LED_R, 1); // boot_mode - red led on
      }
      pinMode(PIN_PU, INPUT);  // pull_up off 
      if(digitalRead(PIN_SW)) // abort
        break;
    }
  }
}

void go_normal_mode()
{
  if(mode != NORMAL_MODE)
  {
    digitalWrite(PIN_LED_R, 0); // boot_mode off
    digitalWrite(PIN_USB_CONNECT, 0); // disconnect usb
    digitalWrite(PIN_CHIP_VCC, 1); // chip power off      
    delay(1000); // discharge c
    digitalWrite(PIN_CHIP_VCC, 0); // power on
    digitalWrite(PIN_USB_CONNECT, 1); // connect usb
    digitalWrite(PIN_LED_G, 1); // normal mode on - green led
    boot_mode_ok = 0;
    mode = NORMAL_MODE;
  }
}

void loop() 
{
  if(digitalRead(PIN_SW)) 
    go_normal_mode();
  else  
    go_boot_mode();
}