You can try any Sharp device code by using the following range of EFCs
Device 17: 43264 to 43519
Device   1: 59648 to 59903
To test these manually, first assign setup code 11602 to the TV button.  Then each of the 256 EFCs for either device can be tested by tapping Setup (don't hold it, and entering in the 5 digit EFC. When you press the 5th digit, the remote will send the IR signal.  Make sure that the procedure is clear by trying this first with EFC 59730, which should send Power toggle.

If you arrange your USB to serial converter to connect to the Comcast, it will easier to try since you can load up 100 or so EFCs at a time, assigning each to a unique button (using both TV and AUX)  and test them by just pressing each button.  If you plan to do that, check to see if the converter uses a FTDI chipset.  If it instead uses a Prolific or Tiao chipset, use the 983 command to blink back the remote signature.  If it is 3039, no problem.  25562 is a JP2 remote and won't work with a Prolific chipset.