TDC Click as its foundation uses the TDC7200, a time-to-digital converter for time-of-flight (ToF) applications for LIDAR and ultrasonic from Texas Instruments. This stopwatch IC is used to measure the time between a single event known as time-of-flight (an edge on START signal) and multiple subsequent events (an edge on STOP signal), which are brought to the onboard SMA connectors marked as START and STOP. The user also can pair this Click board™ with some external board that contains the TDC1000 (ultrasonic analog front-end) and become a part of a complete ultrasonic sensing solution for measurements such as water, gas, and heat flow meter.

The TDC7200 has an internal self-calibrated time base which compensates for drift over time and temperature used to measure time with accuracy in the order of picoseconds. When placed in the Autonomous Multi-Cycle Averaging mode of operation, the TDC7200 can be optimized for low system power consumption. The host can go to sleep to save power, and the TDC can wake it up upon completion of the measurement sequence.

The TDC7200 also needs an external reference clock used to calibrate the internal time-base accurately. All digital circuits inside the device also use this reference clock; thus, the clock has to be available and stable at all times when the device is enabled. For this reason, there is the possibility of selecting an external clock connected to a miniature coaxial N.FL series connector or an internal one by an onboard 8MHz crystal that can be activated via an OEN pin routed on the AN pin of the mikroBUS™ socket. Selection can be performed by onboard SMD jumper labeled as CLK SEL to an appropriate position marked as EXT and INT.

The TDC7200 communicates with MCU using the standard SPI serial interface with a maximum frequency of 20MHz. In addition, it also uses several additional GPIO pins such as the EN pin routed on the RST pin of the mikroBUS™ socket used as a reset to all digital circuits in the TDC7200, TRG pin routed on the PWM pin of the mikroBUS™ socket as a start measurement trigger and INT pin which determine TDC measurement completion.

This Click board™ can be operated only with a 3.3V logic voltage level. The board must perform appropriate logic voltage level conversion before use with MCUs with different logic levels. However, the Click board™ comes equipped with a library containing functions and an example code that can be used, as a reference, for further development.