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RAPI checksums/carrige ID?

I am trying to figure out how to execute "$SC xx V" RAPI commands, using the correct checksum, so I can properly interpret the response using a script. I am a bit baffled how to calculate this though, and was hoping for some explanation:

$= start of RAPI command 

cc = 2-letter command

pp = parameters 

xk = 2-hex-digit checksum - 8-bit XOR of all characters before '^'

ss = optional 2-hex-digit sequence id - response will echo the

sequence id - ss CANNOT be 00, which is reserved as an

invalid value 

\r = carriage return = 13d = 0x0D

Checksum + Sequence ID

$cc pp :ss^xk\r 

I understand how to structure the body of the command, up until the ^xk\r

Can someone explain, for example, how I would know that the proper flag to attach to this command, from the OpenEVSE documentation, is ^64?


How would I go about figuring out the flag to attach to $SC 12 V or any other current rating? 

Thank you very much!

Here is an online calculator.

Enter the full command in the ASCII section including the return for the CheckSum8 Xor.

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