Focusrite AV/C commands

id  value
------------------------------------------------------------------
84  Sample rate (1=44.1k, 2=48k, 3=88.2k, 4=96k, 5=176.4k, 6=192k)
     N.B. setting sample rate can cause the device to reset itself
98  Phantom power (1-4) (1=on, 0=off)
99  Phantom power (5-8) (1=on, 0=off)

To set these values you can use a specially formatted AV/C command:

8 bytes header (0x00, 0xff, 0x00, 0x00, 0x13, 0x0e, 0x03, 0x01)
4 bytes id     (big endian unsigned int)
4 bytes value  (big endian unsigned int)