Here is the PL protocol.

Serial -
Pen
1  1  Rdy  1   0  SWf  0  X15 X14
2  0  X13 X12 X11 X10 X09 X08 X07
3  0  X06 X05 X04 X03 X02 X01 X00
4  0  A-1 SW2 SW1 SW0 A0  Y15 Y14
5  0  Y13 Y12 Y11 Y10 Y09 Y08 Y07
6  0  Y06 Y05 Y04 Y03 Y02 Y01 Y00
7  0  As  A6  A5  A4  A3  A2  A1 

Out of Prox
1   1   0   -   0   0   -   -   - 
2   0   -   -   -   -   -   -   - 
3   0   -   -   -   -   -   -   - 
4   0   -   -   -   -   -   -   - 
5   0   -   -   -   -   -   -   - 
6   0   -   -   -   -   -   -   - 
7   0   -   -   -   -   -   -   - 


USB -
Wacom Specific
1  0   0   0   0   0   0   1   0  (report ID)
2  1  Rdy  1   0  SWf  0  X15 X14 (Raw Data)
3  0  X13 X12 X11 X10 X09 X08 X07
4  0  X06 X05 X04 X03 X02 X01 X00
5  0  A-1 SW2 SW1 SW0 A0  Y15 Y14
6  0  Y13 Y12 Y11 Y10 Y09 Y08 Y07
7  0  Y06 Y05 Y04 Y03 Y02 Y01 Y00
8  0  As  A6  A5  A4  A3  A2  A1 
 Rdy		- Data valid
 X15-X0		- X Coordinate
 Y15-Y0		- Y Coordinate
 SWf		- Button Flag
 SW2-SW0	- Button Data
 A8-(A-1)	- Pressure (0 to 511)

Out of Prox (no device)
1	 0   0   0   0   0   0   1   0  (report ID)
2	 1   0   0   0   0   0   0   0  (Raw Data)
3	 0   0   0   0   0   0   0   0 
4	 0   0   0   0   0   0   0   0 
5	 0   0   0   0   0   0   0   0 
6	 0   0   0   0   0   0   0   0 
7	 0   0   0   0   0   0   0   0 
8	 0   0   0   0   0   0   0   0 

This information is accurate as of this date.  Wacom makes no guarantee that 
this data will be sufficient in the future.  As new tablets are added and 
improved the above formats can change.  It is highly recommended that all 
applications use a standard API to collect data from the Wacom driver.