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+In general everything brings down to figure out:
+-ID
+-Position
+-Possible value range
+
+There seems to be three possible ways to figure that out.
+1) Use USB sniffer together with X-Edit
+   Once you set up X-Edit and usb sniffer, set some option.
+   USB sniffer should report something like this being sent to device:
+   (all numbers here are hex)
+   04 F0 00 00 04 10 00 5E 04 02 41 00 04 30 09 00 07 00 34 F7
+
+   MIDI data is transferred over USB using 32-bit USB-MIDI Event Packets.
+   Byte 0 is Cable Number (high nibble) and Code Index Number (low nibble).
+   Bytes 1, 2 and 3 are data.
+   Every bulk transfer on USB MIDI endpoint contains atleast one such packet
+   (those are sent one after each other).
+   In case of Digitech devices, the Cable Number seems to be 0 (correct me,
+   if I'm wrong).
+   There are three different Code Index Numbers that are being used in this
+   particular case:
+   0x4 - SysEx starts or continues (Byte 1, 2 and 3 from this packet are
+         part of our MIDI message)
+   0x5 - SysEx ends with following single byte (we just need to take Byte 1
+         from this packet)
+   0x6 - SysEx ends with following two bytes (we just need to take Byte 1 and 2
+         from this packet)
+   0x7 - SysEx ends with following three bytes (we need to take Byte 1, 2 and 3
+         from this packet)
+
+   Unused bytes in USB-MIDI packets are supposed to be 0.
+
+   To get SysEx command out of it, apply above rules, so we have:
+      F0 00 00    10 00 5E    02 41 00    30 09 00    00 34 F7
+
+   SysEx message format seems to be formed like this:
+   SysEx start byte - F0
+   Manufacturer ID - 00 00 10
+   Device ID - 00
+   Family ID - 5E (RP)
+   Product ID - 02 (RP250)
+   Procedure - 41 (see MessageID in gdigi.h) 
+
+   As MIDI messages must not contain bytes with MSB bit set, Digitech
+   devices use packing system.
+   First byte contains MSB bits from following 7 bytes (this scheme
+   continues as many times as needed) (see pack_data() and unpack_message() in
+   gdigi.c for details).
+
+   Assuming message has been unpacked, the meaning of next bytes:
+   ID - in this example 30 09
+   Position - in this example 00
+   Value - in this example 00 (can be more bytes long, see below)
+   Checksum - to calculate it, XOR all bytes (of packed message)
+   Every message ends with F7
+
+   So for above example:
+   ID = 3009 (hex) = 12297 (decimal)
+   Position = 0
+   One of possible values is 0. Usually value range is 0 to 99,
+   albeit in some cases it's different - you have to check what values can
+   X-Edit assign (there doesn't seem to be any sanity check in firmware)
+   This is especially needed for IDs that set some effect type.
+      
+2) Save preset patch
+   Patches seem to be simple XML files.
+   Every parameter is written like this:
+     <Param>
+       <ID>65</ID>
+       <Position>2</Position>
+       <Value>0</Value>
+       <Name>Pickup Enable</Name>
+       <Text>Off</Text>
+     </Param>
+   ID is ID, Position is Position and Value is one of possible values.
+   To get all possible values you can:
+     do
+       change value to next one possible in X-Edit
+         (for example next effect type)
+       save new patch
+       check patch file and note the change
+     while you don't have all possible values
+3) Use gdigi
+   After starting gdigi turn the knobs on your device.
+   Check out console output, you should notice something like this:
+      ** Message: Received parameter change ID: 210 Position: 4 Value: 0
+   ID is ID, Position is Position and Value is one of possible values.
+   To get all possible values keep turning knobs and watch the output.
+   If you change effect type usually there's more messages - where,
+   usually the first one is type change, and rest are default values.
+   This way you *CANNOT* gather all information (there're X-Edit only
+   controlled values, check device manual for more information).