Build Instructions

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• 1

  Upload the sketch and set fuse to disable reset

  Upload the sketch using the Arduino UNO as SPI programmer. Use 1mm diameter pogo pins to connect to the board:

  
  Set the clock to 1MHz (internal), this will reduce the power consumption, we do not need speed. Upload the following sketch:
  

  static byte timerDelay = 255;
  bool timerDirectionUp = false;
  
  void setup()
  {
    DDRA  = 0xFF; // Set all pins on PORT A to outputs
    PORTA = 0x00; // Set all outputs to LOW
    DDRB  = 0x0F; // Set all pins on PORT B to outputs
    PORTB = 0x00; // Set all outputs to LOW
    
    cli();        
    TCCR1A = 0;               // Timer/Counter Control Registers
    TCCR1B = 0;               // Timer/Counter Control Registers
    TCNT1  = 0;               // Timer Counter
    //OCR1A = 3906;             // Output Compare Registers   0.256 * 3906 = 1000ms    
    OCR1A = 30;
    TCCR1B |= (1 << WGM12);   // Clear Time and Compare CTC
    TCCR1B |= (1 << CS12);    // 256 prescaler 1Mhz/256 = 0.256ms
    TIMSK1 |= (1 << OCIE1A);  // Output Compare A Match Interrupt Enable
    sei();
  }
  
  ISR(TIM1_COMPA_vect) // timer interrupt
  {
    if(timerDirectionUp)
    {
      timerDelay++;
      if (timerDelay > 200) timerDirectionUp=false;
    }
    else
    {
      timerDelay--;
      if (timerDelay < 5) timerDirectionUp=true;
    }
  }
  
  void loop()
  {
    cli () ;              // Turn off interupt
    PORTA |= (1<<0);      // set pin 0 (PA0) to HIGH
    __asm__("nop\n\t");   // Wait for 1 clock cycle
    PORTA &= ~(1<<0);     // set pin 0 to LOW
    PORTB |= (1<<3);      // set pin 11 (PB3) to HIGH
    __asm__("nop\n\t");   // Wait for 1 clock cycle
    PORTB &= ~(1<<3);     // set pin 11 to LOW
    sei () ; // Turn on interupt
    delayMicroseconds(timerDelay*10);
  }

  After uploading the sketch, disable the reset fuse in CMD (find your settings in the Arduino verbose output):
  

  C:\Program Files (x86)\Arduino\hardware\tools\avr\bin>avrdude -CC:\Users\username\AppData\Local\Arduino15\packages\ATTinyCore\hardware\avr\1.2.2/avrdude.conf -v -pattiny84 -carduino -PCOM3 -b19200  -Uhfuse:w:0b01010111:m

• 2

  Solder the LED's to pin 0 and 11

  I picked pin 0 and 11 since these are the closest to the USB connector (head of the spider) after the 5V and GND. 5V and GND are used for the first legs. Unfortunately pin 11 is the reset pin and for that reason the reset was disabled in step 1 so that it can be used as an output.
  

  
  The anode leg (+, long leg) connects to the outputs pin, the cathode to the top of the USB connector. The entire USB connector is connected to ground. Trim the legs, but keep the trimmed ends.
  

• 3

  Solder the legs

  Solder the resistor, sticking out from the top on pins 5V, GND, 1, 3, 5, 6, 8 and 10.

  Bend the legs slightly so that it can stand.
  

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