/// <summary>
/// Write a PiJuice command
/// </summary>
/// <param name="command">The PiJuice command</param>
/// <param name="data">The data to write</param>
internal void WriteCommand(PiJuiceCommand command, ReadOnlySpan <byte> data)
{
byte tries = 0;
Span <byte> buffer = stackalloc byte[data.Length + 2];
data.CopyTo(buffer.Slice(1));
buffer[0] = (byte)command;
buffer[buffer.Length - 1] = GetCheckSum(data, checkLastByte: true);
// When writing/reading to the I2C port, PiJuice doesn't respond on time in some cases
// So we wait a little bit before retrying
// In most cases, the I2C read/write can go thru without waiting
while (tries < MaxRetries)
{
try
{
_i2cDevice.Write(buffer);
return;
}
catch (IOException ex)
{
tries++;
if (tries >= MaxRetries)
{
throw new IOException($"{nameof(WriteCommand)}: Failed to write command {command}", ex);
}
DelayHelper.DelayMilliseconds(ReadRetryDelay, false);
}
}
}
/// <summary>
/// Read data from PiJuice
/// </summary>
/// <param name="command">The PiJuice command</param>
/// <param name="length">The length of the data to be read</param>
/// <returns>Returns an array of the bytes read</returns>
internal byte[] ReadCommand(PiJuiceCommand command, byte length)
{
byte tries = 0;
Span <byte> outArray = stackalloc byte[length + 1];
outArray.Clear();
// When writing/reading the I2C port, PiJuice doesn't respond on time in some cases
// So we wait a little bit before retrying
// In most cases, the I2C read/write can go thru without waiting
while (tries < MaxRetries)
{
try
{
_i2cDevice.Write(new byte[] { (byte)command });
_i2cDevice.Read(outArray);
var checksum = GetCheckSum(outArray);
if (checksum != outArray[length])
{
outArray[0] |= 0x80;
checksum = GetCheckSum(outArray);
if (checksum != outArray[length])
{
tries++;
if (tries >= MaxRetries)
{
throw new InvalidDataException($"{nameof(ReadCommand)}: Invalid checksum read command {command}, checksum {checksum}");
}
DelayHelper.DelayMilliseconds(ReadRetryDelay, false);
continue;
}
}
break;
}
catch (IOException ex)
{
tries++;
if (tries >= MaxRetries - 1)
{
throw new IOException($"{nameof(ReadCommand)}: Failed to read command {command}", ex);
}
DelayHelper.DelayMilliseconds(ReadRetryDelay, false);
}
}
return(outArray.Slice(0, length).ToArray());
}
/// <summary>
/// Write a PiJuice command and verify
/// </summary>
/// <param name="command">The PiJuice command</param>
/// <param name="data">The data to write</param>
/// <param name="delay">The delay before reading the data</param>
internal void WriteCommandVerify(PiJuiceCommand command, ReadOnlySpan <byte> data, int delay = 0)
{
WriteCommand(command, data);
if (delay > 0)
{
DelayHelper.DelayMilliseconds(delay, false);
}
var response = ReadCommand(command, (byte)data.Length);
if (!data.SequenceEqual(response))
{
throw new IOException($"{nameof(WriteCommandVerify)}: Failed to write command {command}");
}
}
