private void Write4Bits(int value)
{
ushort gpio = mcp23017.ReadGpioAB();
for (int i = 0; i < 4; i++)
{
gpio &= (ushort)(~(1 << dataPins[i]));
gpio |= (ushort)(((value >> i) & 0x01) << dataPins[i]);
}
mcp23017.WriteGpioAB(gpio);
gpio |= (ushort)(1 << enablePin);
mcp23017.WriteGpioAB(gpio);
gpio &= (ushort)((~(1 << enablePin)) & 0xFFFF); // who promotes to int on bit negation?!?
mcp23017.WriteGpioAB(gpio);
}