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peripherals: LC709205F: Replace manual CRC8 with CRCEngine #154

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peripherals: LC709205F: Replace manual CRC8 with CRCEngine #154

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26 changes: 3 additions & 23 deletions src/Emulator/Peripherals/Peripherals/I2C/LC709205F.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -121,7 +121,7 @@ private byte ReadWithCRC(Registers register, int offset)
return step == TransactionStep.MSB ? (byte)(result >> 8) : (byte)result;
// Third byte is CRC of the value
case TransactionStep.CRC:
var crc = CalculateCrc8(new byte[] {(byte)(SlaveAddress << 1), (byte)register, (byte)((SlaveAddress << 1) + 1), (byte)result, (byte)(result >> 8)});
var crc = crc8Engine.Calculate(new byte[] {(byte)(SlaveAddress << 1), (byte)register, (byte)((SlaveAddress << 1) + 1), (byte)result, (byte)(result >> 8)});
return (byte)crc;
default:
throw new Exception("unreachable state");
Expand Down Expand Up @@ -153,28 +153,6 @@ private void WriteWithCRC(Registers register, int offset, byte value)
RegistersCollection.Write(realAddress, underlyingValue);
}

private byte CalculateCrc8(byte[] data)
{
var result = 0x00;
foreach(var b in data)
{
result = (byte)(result ^ b);
for(var i = 0; i < 8; ++i)
{
if((result & 0x80) != 0x00)
{
// Polynomial x^8+x^2+x+1
result = (byte)((result << 1) ^ 0x07);
}
else
{
result = (byte)(result << 1);
}
}
}
return (byte)result;
}

private void DefineRegisters()
{
Registers.TimeToEmpty.Define(this)
Expand Down Expand Up @@ -293,6 +271,8 @@ private int SlaveAddress
private uint cellTemperature;
private uint ambientTemperature;

private static readonly CRCEngine crc8Engine = new CRCEngine(CRCPolynomial.CRC8_CCITT, reflectInput: false, reflectOutput: false);

private enum TransactionStep
{
LSB,
Expand Down