Thanks for your responses. US 600 (typical price for these AD boards ) I'ts very expensive for me and for my app I don't require it.
problem statement is:
I need to control a synchronous motor position & velocity
I need to capture a position signal from an encoder (8 bits at high sampling rate) and send the command outputs (three for synchronous motors, 30bits for three 10 bits resolution PWM), these PWM outputs are generated by microcontroller. All I need is to transfer the 30 bits to the microcontroller. The commanded outputs are calculated by a complex nonlinear controller. Sampling rate is about 1ms, but the calculations are complex and I can't waste long time in communications.
for example RS232 at 115.000 kbps
40 bits of time =347us too long time wasted for calculation.
I need a cheep solution based on above comments
thanks for your help.
nebisman