Question About Calculating Checksum in a StreamDevice Protocol

[Huishan via Tech-talk <tech-talk at aps.anl.gov>]

Hello everyone,

    I have a question about writing a StreamDevice protocol for the following command: 55 AA 05 04 byte1 byte2 byte3.

    The last three bytes of the command need to change dynamically. The first two bytes represent the current value in hexadecimal format. The third byte is a checksum, which is calculated by adding 0x05, 0x04, byte1, and byte2 using hexadecimal addition.Is there a way to have the checksum calculated automatically in a StreamDevice protocol? If so, what should I use in the protocol file as a placeholder for the calculated value?

    If StreamDevice doesn't support calculations like this, does that mean I have to calculate the checksum manually every time before sending the command?

    Any suggestions or examples would be greatly appreciated.Thank you!

                                                                                                                         Huishan