The gist is to use a little 3 point 'history' of readings to look for single point 'glitches' and then remove them.

Filtering and baseline subtraction also helps:

/***************************************************************************** CapacitiveTouchTest: Playing with the capacitive touch inputs on the ESP32 Based on the Espressif ESP32 TouchRead example code. Adding in de-glitching and smoothing of the reported values and dynamic baseling tracking. Touch0 is T0 which is on GPIO 4. J. Price, 2022. -- Based on the Espressif ESP32 TouchRead example code. The touchRead function in the ESP Arduino API seems to be susceptible to noise. A number of people have reported 'glitching' in the signal. (Sharp, single-point spikes in the data.) This code adds a simple de-glitching feature and provides the option to smooth the data to reduce noise. Feel free to play with the smoothing constants to fit your application. *****************************************************************************/ float p1=0.0, p2=0.0, p3=0.0; // 3-Point history float raw = 0.0; // Current reading float baseline = 0.0; float smoothed = 0.0; unsigned long count=0; // Smoothing factors. The closer to one (1.0) the smoother the data. Smoothing // introduces a delay. const float dataSmoothingFactor = 0.95; const float baselineSmoothingFactor = 0.9995; /*****************************************************************************/ void setup() { Serial.begin(115200); delay(1000); // give me time to bring up serial monitor Serial.println("Smoothed Raw De-Glitched"); // Intialize history and smoothed value to an average of a few readings for (int i = 0; i<100; i++){ raw += touchRead(T0); delay(10); } raw = raw /100; p3 = raw; p2 = raw; p1 = raw; smoothed = raw; baseline = raw; } /*****************************************************************************/ void loop() { // Current value raw = touchRead(T0); p1 = raw; // Latest point in the history // Glitch detector if (abs(p3-p1) < 5) { // The latest point and the two points back are pretty close if (abs(p2-p3) > 3) { // The point in the middle is too different from the adjacent points -- ignore p2 = p3; } } // Smooth the de-glitched data to take out some noise smoothed = p3 * (1 - dataSmoothingFactor) + smoothed * dataSmoothingFactor; // Dynamic baseline tracking -- a much longer view of the de-glitched data if ( count > 50 ){ baseline = p3 * (1 - baselineSmoothingFactor) + baseline * baselineSmoothingFactor; } // Shift the history p3 = p2; p2 = p1; Serial.println( String(smoothed - baseline) + "," + String(raw - baseline + 20) + "," + String(p3 - baseline + 10) ); // get value using T0 delay(30); }