From Cricut Hacking Wiki
The send command follows the same standard, number of bytes to expect, the command byte and filler values to the standard command length of 4.
Send: 04 12 00 00 00 00
Included below are the results for this command from different machines with different firmware versions. The actual version number is identical to the version number displayed when the Cricut model first starts up. (Mini does not have a screen, so it's values are assumed based on the other commands.
The first byte is the number of bytes to expect. The third byte displayed appears to refer to a model identifier, the second byte probably allows for growth. The fifth byte displayed matches the firmware major version, the fourth byte probably allows for growth. The seventh and last byte displayed matches the firmware minor version, the sixth byte probably allows for growth.
Cricut Cake : 20 (v2.34 = 0x0002 0x0022)
Recv: 06 00 14 00 02 00 22
Cricut Expression : 20 (v2.31 = 0x0002 0x001F)
Recv: 06 00 14 00 02 00 1F
Cricut Mini : 0x1e (v0.23 = 0x0000 0x0017), this may refer to the firmware version of the PIC Microcontroller. The factory firmware version for this specific mini was 19 and the user has upgraded since then.
Recv: 06 00 1e 00 00 00 17
Cricut Personal : 10 (v1.34 = 0x0001 0x0022)
Recv: 06 00 0a 00 01 00 22