2. Hardware overview

2.1 Identifying Ground points

By looking at the PCB, we can identify a few potential candidates for the Ground points:

We can use the digital multimeter in continuity mode to test the GND points, which can be identified when a "beep" sound is heard:

• Confirmed GND points

2.2 Identifying UART pins (TX, RX, GND, 3.3V)

In the following video, I demonstrate how to identify the pins on the UART Interface using the digital multimeter:

The following outlines the characteristics of each pin:

1. TX: fluctuates from 2.5 to 3.3V

2. RX: fluctuates slightly before stabilizing at 3.3V

3. GND: drops and stabilizes at 0.00V

4. 3.3V: fluctuates slightly before stabilizing at 3.3V (more erratic fluctuation that RX)

2.3 Taking a closer look at TX+RX

In the following video, we focus on the voltage values of the TX and RX pins right after the router is powered ON:

2.4 UART pins