If you are working on ezDSPF28335 and cannot get the eCAP examples to work, check jumper JR6 (Pg 36 of ezDSPF28335 Tech Ref). The factory default should be Configuration B = GPIO24 routed to MUX GPIO22_24.
I found that my board had been shipped with configuration A = GPIO22 routed to MUX GPIO22_24.