Feb.16 Tacho Motor Encoder

Need interrupts to count the degrees from the tachometer in the motor.
If I understand right this is typically done by quad-code, 
where the signal changes indicated how much the motor has turned. 
Following are just good references found for now. 
The links will be needed for references if really help:
googled "quad-code for beginners" since that what I am.

• NI's Encoder Measurement: How-To Guide
• NI's Quadrature Encoder Fundamentals
• Encoder Measurments: How-To Guide 
• see Figure 5. X1 Encoding for how signal looks
• fpga4fun  see Quadrature Decoder
• fpga = field programable gate array

Reviewing existing motor code:

motorAvrSetPwrBrake(cyg_uint32 pa_nOutputPort, cyg_int32 pa_nPercent, int pa_nBrake)

• pa_nPercent is:
• passed in as 32 bits, but ...
• assigned to a 8 bit variable
• sizes should match
• ditto for   pa_nBrake
• Also check for motor power between -100 and 100 should be in avr code. If in FB code, a new FB code could forget the check and bad data be sent.