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DI #1 Wont read frequency or speed input (LinkPlus G3)

Michael Lusby

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Hi there,

I have connected the vehicle speed sensor input into digital input #1. The input is configured with a pull-up resistor and the sensor is nothing more than a magnetic reed switch driving the line low as a tooth passes. Digital input #1 is unable to read the frequency or speed of this input however when configured as a general input the level of the signal is able to recognised as on/off. Interestingly configuring digital input #3 to be a speed input with the same settings as digital input #1 and connecting the vehicle speed sensor to digital input #3 results in the ecu recognising the frequency of the square wave.

Reading through the manual says that digital input #1 is fine for a frequency/speed input, whats going on? is this is a firmware/software bug or is my LinkPlus G3 faulty? Surely if the ecu is able to quantise the signal to low and high conditions for a GP input it simply extends this behaviour to measure frequency/speed by counting the number of edge transitions (edge depending on which triggering option chosen falling or rising) in a given period of time.

Link in question is LinkPlus G3 Firmware Rev 1.7.1 and PCLink 3.34

Whats the deal?

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