MIKROE Watchdog Click is a compact add-on board that contains a simple countdown timer for a wide variety of applications. This board features the TPS3430, a standalone watchdog timer with a programmable watchdog window and programmable reset delay from Texas Instruments. The TPS3430 has the watchdog output reset delay set by factory-programmed default delay settings or programmed by an external capacitor. It achieves 2.5% timing accuracy at the typical temperature of 25°C and can be disabled via two SET pins to avoid undesired watchdog timeouts during the development process or Power-On. This Click board™ can be used as a countdown timer in MCU, DSP, FPGA, ASIC, and many more.

Watchdog Click is based on the TPS3430, a standalone watchdog timer with a programmable watchdog window and reset delay from Texas Instruments. This high-accuracy programmable timer with the disable feature achieves 15% watchdog timing accuracy over the extended temperature range from –40°C to +125°C. A window watchdog is typically employed in safety-critical applications where a traditional watchdog timer is inadequate. With a traditional timer, there is a maximum time in which a pulse must be issued to prevent the reset from occurring. However, in a window watchdog, the pulse must be issued between a maximum lower window time and the minimum upper window time set by the programmable timeout pin and two logic input pins.

This Click board™ communicates with MCU using several GPIO pins and offers both programmable watchdog timeout and reset delay. The two pins that this Click board™ uses represent a watchdog input and output, with additional two logic inputs with whom the user can select the watchdog window ratios, timeouts and disable the watchdog timer.

The watchdog input pin labeled as WDI routed on the PWM pin of the mikroBUS™ socket is ignored for the watchdog reset delay upon Start-Up. After Start-Up, the watchdog input signal must arrive within the watchdog window to prevent a watchdog reset whose delay duration may be configured with CRST SEL on-board jumper. The user has two options, leaving the CRST pin pulled high with a pull-up resistor or to connect the CRST to a capacitor connected to GND. Similarly to the watchdog reset delay, the user can also configure the watchdog timeout using the S0 and S1 pins, routed on the RST and CS pins of the mikroBUS™ socket, and CWD SEL on-board jumper. This jumper can connect the CRST pin with a pull-up resistor or with a capacitor connected to GND.

When a watchdog fault occurs due to an incorrectly timed watchdog input signal, the WDO pin activates and performs the transition to logic low state for the period of the watchdog reset delay, which is also indicated with a red LED labeled as WDT FLT. When delay expires, the WDO pin deactivates and returns to a logic high state. When the watchdog is disabled using S0 and S1 pins, the watchdog input is ignored, and the WDO pin is in a Hi-Z and remains logic high due to the R5 external pull-up resistor.

This Click board™ is designed to operate with both 3.3V and 5V logic voltage levels selected via the VCC SEL jumper. It allows for both 3.3V and 5V capable MCUs to use the communication lines properly. However, the Click board™ comes equipped with a library that contains functions and an example code that can be used, as a reference, for further development.

• Interface: GPIO
• Compatibility: mikroBUS™
• Dimensions: 28.6 x 25.4mm
• Input Voltage: 3.3V or 5V
• Maximum Output Current: 10mA
• Operating Temperature Range: -40°C to +125°C
• Watchdog Reset Delay (RPU): Min. 8.5ms, Typical 10ms, Maximum 11.5ms

• Schematic
• TPS3430 Datasheet
• mikroSDK
• GitHub