I am trying to obtain engine speed from a hall-effect sensor that outputs 5V TTL signal using a compactrio 9014 with a NI-9401 and a NI-9221 module. First, i connected its output to the analog input (i.e 9221) and tried to use the tone-extractor vi to obtain frequency and subsequently, calculate my engine speed, but i'm getting zero output from the frequency terminal of the tone-extractor. Then i tried connecting to the digital input (NI-9401); i'm able to count high and low periods, and the rising edge (on the fpga side) but I have no clue how to convert this to engine speed in revolutions per minute (on the RT side). I tried using the ticks in FPGA and obtaining ticks/count like was done in quadrature encoder.vi example, but it didn't work. My ticks/count increments to 154 and stops there. I believe someone out there might have accomplished this task; please help me out. Thanks.
