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Guide to Interpreting Compensation Capacitance  Calibration Value for QTouch® Library

Last modified by Microchip on 2026/03/19 14:28

This page outlines the process for calculating the Compensation Capacitance (CC) for a device using the node_comp_caps value in the touch application. Also known as the CC calibration value, it is determined during the calibration phase and can be accessed for each touch button as follows:

uint16_t cc_value = ptc_qtlib_node_stat1[SENSOR_NUMBER].node_comp_caps;

Here, node_comp_caps is a member of the qtm_acq_node_data_t structure:

typedef struct {
 uint8_t node_acq_status;
 uint16_t node_acq_signals;
 uint16_t node_comp_caps;
} qtm_acq_node_data_t;

These unsigned 16-bit node_comp_caps values, stored in the Peripheral Touch Controller (PTC) CC register format, can be obtained using the helper function uint16_t get_sensor_cc_val(uint16_t sensor_node) in the touch.c file.

To calculate the CC value for a specific device, select the desired device from the Select Device dropdown menu and enter the Node Compensation capacitance value (node_comp_caps). The calculator then determines the CC value (in pF) for both Selfcap and Mutual cap based on the selected device. Additionally, the tool provides details on the CC register format and the maximum sensor capacitance supported for the chosen device.

Compensation Capacitance Calculator

Compensation Capacitance Calculator