Raise NotImplementedError when Operation field in packet 0x38 is set to 2 (load data)

[mjuenema]

Currently only requesting satellite data is (will be #25) implemented so the only valid value for the Operation field of Request Packet 0x38 is 1. Setting this field to 2, i.e. trying to load data into the satellite, should raise NotImplementedError (any other value will return an error from the GPS, correct?).

While I could implement loading data into the GPS I am (a) unable to test this and (b) don't want to "brick" my GPS ;-)

[mjuenema]

In fact only some GPS support loading of data. For instance the manual of the Thunderbolt-E says that this field must be set to 1.
Unfortunately the structure of the request body appears to vary between GPS. For Thunderbolt-E it is 3 bytes while the Copernicus II adds a 4th byte "length of data".

• Does the Copernius II accept 3 byte requests?
• If not, how could the code deal with it if the model of the GPS is not known?
• Should one query the hardware version (0x1c) first and then format 0x38 accordingly?