code: func (t *TM1638Driver) SendChar(pos byte, data byte, dot bool) {
  	if pos > 7 {
  		return
  	}
  	var dotData byte
  	if dot {
  		dotData = TM1638DispCtrl
  	}
  	t.sendData(pos<<1, data|(dotData))
  }
docs: // SendChar sends one byte to the specific position in the display