11 Application Schematic

The basic power supply connections for the ATSAMW25 module are shown in the following figure. The test points shown (TP1 – TP6) must be added in case Microchip is required to debug the design.

The Wi-Fi chip can use its own internal oscillator for a Real Time Clock (RTC) or it can use an external 32.768 KHz clock provided on the RTC pin. Using an external clock derived from a crystal oscillator can be used as a more accurate sleep timer for the Wi-Fi chip than its own internal oscillator. This, in turn, can reduce sleep current. If power consumption during sleep is a priority, a 32.768 KHz crystal can be added to the SAM D21 module, as shown in the reference design. The design shown above displays a connection from pin 15 (PA22) to pin 5 (GPIO_1).

GPIO_1 is the input pin for the Wi-Fi’s Real Time Clock. PA22 can be configured to output a 32.768 KHz RTC clock, derived from the 32.768 KHz crystal, to be used as the source for the Wi-Fi’s RTC. If cost is a priority versus power consumption, the 32.768 KHz crystal can be left off of the design and the PA22 – GPIO_1 connection can be deleted.