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Digital Inputs

EFI Tuning Fundamentals

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Hi, so Digital Input always will work on the on and off state, but how this works in the clutch switch, and with the frequency with speed inputs, turbo speed inputs, driver switches to turn functions such as launch control or traction control on or off in the ECU this can be controlled with on/off state but these can be modified with ECU files also? And, when an input is on the on-state receives Voltage right? So when it is on off there´s already a difference of voltage because it changed to zero, and in what case when a circuit the switch is on and connected to ground, it will see ground or zero volts based on experience building wires? Any help is appreciated I don´t know much about these things.

A digital input can often be measured in several ways:

-- state (i.e. On/Off; Hi/Lo, Active/Inactive). This is what would be used for a switch such as your clutch switch.

-- frequency (i.e. hz, rpm). This would be used for inputs that measure speed

-- pulse width (ie. time or duty cycle). This might be used for some sensors indicating a position. It can also be used to provide a speed value if converted to a frequency.

There are many ways to interpret the active or ON state of a digital input. Often active low is used, as the ECU provides a voltage to the signal pin through a pullup resistor, and the switch just needs to be tied to ground to become active. Some ECU's may have a setting allow you to define a threshold voltage and a polarity -- so you can define -- when the voltage is above or below the threshold make the input active. That is often useful if you are just measuring a signal that has to work with another device.