Node-red-contrib-mcp23017chip

General
71

I tend to use a set of functions that help me avoid typos...

//Get bit
function getBit(number, bitPosition) {
  return (number & (1 << bitPosition)) === 0 ? 0 : 1;
}

//Set Bit
function setBit(number, bitPosition) {
  return number | (1 << bitPosition);
}

//Clear Bit
function clearBit(number, bitPosition) {
  const mask = ~(1 << bitPosition);
  return number & mask;
}

//Update Bit
function updateBit(number, bitPosition, bitValue) {
  const bitValueNormalized = bitValue ? 1 : 0;
  const clearMask = ~(1 << bitPosition);
  return (number & clearMask) | (bitValueNormalized << bitPosition);
}

e.g...

let readVal = 0, writeVal = 0;
let writeByte = 0x14, readByte = 0x12, bit = bitNum;
if (bitNum >= 8) {
    writeByte = 0x15;
    readByte = 0x13
    bit = bitNum - 8;
}

readVal = _aBus.readByteSync(_addr, readByte); //read the value
writeVal = updateBit(readVal, bit, newState); //set/reset the bit
_aBus.writeByteSync(_addr, writeByte, writeVal & 0xFF); //write back new value
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