code: func SpiMode(polarity uint8, phase uint8) {
  	const cpol = 1 << 3
  	const cpha = 1 << 2
  
  	if polarity == 0 { // Rest state of clock = low
  		spiMem[csReg] &^= cpol
  	} else { // Rest state of clock = high
  		spiMem[csReg] |= cpol
  	}
  
  	if phase == 0 { // First SCLK transition at middle of data bit
  		spiMem[csReg] &^= cpha
  	} else { // First SCLK transition at beginning of data bit
  		spiMem[csReg] |= cpha
  	}
  }
docs: // SpiMode: Set polarity (0/1) and phase (0/1) of spi clock
  // default polarity=0; phase=0