Hello, the same byte is sent twice in the Arduino code because the second byte is the checksum, which is useful when writing more than one byte as a check on the data being sent. Currently, the Arduino code is only set up to send single bytes but still needs to comply with the protocol. You can see the full write method in our open source API here https://github.com/sensel/sensel-api/blob/1139c84b35837dce94f49ef926ca5e9d55693fd7/sensel-lib/src/sensel_register.c#L102.
Additionally, the LED commands do not use write register, they use the variable size write register, which can be found here in the open source api: https://github.com/sensel/sensel-api/blob/1139c84b35837dce94f49ef926ca5e9d55693fd7/sensel-lib/src/sensel_register.c#L199
We will be adding more functionality and documentation to the Arduino API in the future, but do not have a release date at this time.
