CH Pedals problem

I plugged my CH pedals with a gamepad to the gameport port in my soundcard, and i see only 18 values per one axis in the raw data during calibration. So when i move one of the pedals forward, iget only 8 situations of the axis condition, which is very annoying.Can someone help me solve this problem?I tried to connect the pedals also with another gameport device, and there was the same problem.