A module for Sensiron SCD40

[Radyr]

My first attempt at a module for the Sensiron SCD40.

It should also work with the SCD41 and SCD43 but not tested as I dont have those to hand.

[gfwilliams]

This looks great, thanks! Please could you convert:

  REQUEST_SINGLE_LOOKUP : Uint8Array([0x219d>>8,0x219d]),
  REQUEST_SINGLE_LOOKUP_RHT : Uint8Array([0x2196>>8,0x2196]),
  // and so on

to just:

  REQUEST_SINGLE_LOOKUP : [0x21,0x9d]),
  REQUEST_SINGLE_LOOKUP_RHT : [0x21,0x96]),
  // and so on

While Uint8Array is good for big arrays of bytes, there's quite a bit of overhead for just storing 2 bytes worth of data, so in this case just storing the data in a standard array should be a lot better.

[Radyr]

Thats useful to know, it also looks a lot nicer

[gfwilliams]

Thanks! I've just changed the code a bit though, because as you had it you were still putting the full 16 bit data into the second array item (when what you really wanted was just the low 8 bits).

I'm pretty sure it's ok, but please could you give it a test? Changes I made are e46466e

[Radyr]

Apologies, I didnt spot the change of the values. I was in two minds to do that initially.

I've tested it against the chip and getting good results still

[Radyr]

I was having another think about the measurements. Should the raw data also be returned?

I haven't looked into it, but I'm guessing it might be more efficient to store the data as returned from the sensor, rather than the converted values.

[gfwilliams]

I think what you're doing (sending back the converted data) is absolutely fine. If someone really wants the raw data they can always modify it later or access the sensor via I2C themselves.