Hi,
The developer has to decide this.
There are many different ways
* sending two 12 bit words as three 8 bit bytes needs the least uncompressed bit to transmit. But it is hard to receive and decode.
* sending one 12 bit word as two bytes is good to decode. Maybe 7bits LSB plus the MSBit = low in one byte, then the rest 5 bits and the MSBit = high. Easy to decode, but nit human readable.
* transferring the 12 bits into an ASCII string "1234" folowed by [Cr] [Lf] are 6 bytes to transmit, but human readable.
* and there are numerous other solutions.
Klaus