1 measuring position, 2 measuring pressure – Interlink Electronics FSLP Sensor User Manual

Page 12

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Force Sensing Linear Potentiometer (FSLP)

Integration Guide

5.1 Measuring Position

Step 1: Clear Charge on Sensor

 Enable all lines as outputs and set them to 0 Volts. This will clear all charge from the

sensor and help reduce noise on readings.

Step 2: Set Up Appropriate Driveline Voltages

 Configure sensor terminal 2 as output high (+Vcc).
 Configure sensor terminal 3 as output low.
 Configure the pin connected to the bottom of resistor R

as an output low. This drains

any charge that may have capacitively coupled to the sense line during the
transitions of sensor terminals.

 Configure the GPIO pin connected to the bottom of R

as a high impedance input.

 Configure sensor terminal 1 as an ADC input.

Step 3: Wait For Voltage to Stabilize

 The voltage generated on the sense line can have an input resistance ranging from

2kΩ to 300kΩ. Higher resistances result from very light pressure on the sensor.
Depending on the input impedance of the ADC, allowing five to ten microseconds
before taking the measurement will help to increase the sensitivity of the sensor and
detect light touches.

Step 4: Take the measurement

 Start the A/D conversion and store the result. An 8-bit ADC will yield a result within 0

and 255 counts. This value is proportional to the physical distance from sensor
terminal 3.

5.2 Measuring

Pressure

Step 1: Setup the appropriate drive line voltages

 Configure sensor terminal 2 as an output high (+Vcc).
 Configure sensor terminal 1 as an ADC.
 Configure sensor terminal 3 as an ADC.
 Configure the pin connected to the bottom of R

as an output low.

Step 2: Wait for voltage to stabilize

 The voltage generated on the sense line can have an input resistance ranging from