18.2 Tuning the Slider/Wheel Sensor

For instance, two buttons and a three-channel self-capacitance slider are configured. Let the buttons B0, B1, and the Key sensors that form the slider sensor be Slider0[0], Slider0[1], and Slider0[2].

The Buttons, Slider/Wheel data are displayed in the data visualizer control panel view, as shown below.

The following steps describe the procedure for tuning the slider/wheel sensors.

Step 1:

Make a touch on each key sensor Slider0[0], Slider0[1], and Slider0[2] and note the delta values. For example, the delta observed on slider0[0] is shown below.

Set the individual key sensor threshold to half the value of the delta value observed. In this case, the key threshold should be set to 60.

Step 2:

Set the calculated key threshold on Step 1 as the SW Threshold and verify the slider sensor goes to detect when the touch made on the individual sensors is as shown below.

Step 3:

Scroll over the slider sensor back and forth between start and end corners and record the SW delta on a CSV file using the File logger utility.

To use file logger, follow the instructions below:

  1. Switch to Edit mode by checking the edit box at the bottom of the debug control panel.
  2. Open the File Logger element Configurations -> Utilities -> File Logger.
  3. Minimize the QTouch Data Visualizer view window by double-clicking on the title bar.
  4. In the File Logger view, click the file browser and select the file name to log data.
  5. Click the SWDelta0 connector, drag and plug it to the file logger socket, as shown in the figure below.
  6. Now click the Start/Stop button to log the data.
  7. After logging complete, remove the SWDelta0 connection, uncheck the edit mode check box and close the File Logger.

Step 4:

Open the file log and identify the lowest SWDelta0 value from the samples. A few samples of the SWDelta0 collected from the Slider_delta.csv file are listed below.

103, 102, 101, 106, 98, 92, 86, 82, 78, 76, 78, 86, 0, 118, 113, 109, 105, 102, 100, 106, 102, 93, 86, 80, 76, 73, 72, 73, 79, 88, 90, 90, 89, 89, 89, 90, 94, 87, 81, 76, 72, 71, 69, 72, 81, 89, 94, 98, 100, 102

Set the SW threshold less than the identified minimal value “69”. In this case, the SW threshold is set about 15 counts less than the observed value, which is 54. Repeat step3 and step4 for a couple of iterations and tune the SW threshold based on the logs.

The Buttons, Slider/Wheel data after the tuning are given below.