Changes

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The angle of the data is not aligned with the natural axis of the device. It seems that the first sample of the first packet is in fact looking at a -10° angle, not 0°. Needs confirmation.

A full revolution will yield 90 packets, containing 4 consecutive readings each.

*speed is a two-byte information, little-endian. It represents the speed, in 64th of RPM (aka value in RPM represented in fixed point, with 6 bits used for the decimal part).

*Data 0 to Data 3 are the 4 readings. Each one is 4 bytes long, and organized as follows :

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byte 0 : Distance 7:0

Byte 2 and 3 are the LSB and MSB of the strength indication. This value can get very high when facing a retroreflector.

The algorithm is as follows, provided that `data` is the list of the 20 first bytes, in the same order they arrived in.

return int( checksum )

The periodicity of the data is 1446 bytes.