The antenna presence test can be implemented also in the application software side by deploying available General-Purpose Input/Output (GPIO)s.
One GPIO (P0.27) is configured as high output and connected to the antenna feed through a resistor (R3) and RF choke inductor (L1). Another GPIO (P0.26) is used to read the DC level of the antenna feed. If the DC level is low, the antenna is DC grounded and connected.
An example of the implementation is shown in Antenna presence test using GPIOs.
Figure 1. Antenna presence test using GPIOs
| Reference | Description |
|---|---|
| A1 | Antenna, DC grounded |
| R1 | 0R |
| R2 | 0R, not assembled by default |
| R3 | Antenna detection resistor (10 kΩ) |
| L1 | Antenna detection, RF choke inductor (56 nH) |
| L2 | Antenna matching component (value depends on selected antenna) |
| C1 | Antenna detection, DC block |
| C2 | Antenna detection, RF grounding (56 pF) |
| C3 | Antenna matching component (value depends on selected antenna) |
| C4 | Antenna matching component (value depends on selected antenna) |
The following components are highlighted in Layout of antenna presence test using GPIOs:
- Test cable
- Antenna matching circuit
- Antenna detection components
- Antenna keep-out area
Figure 2. Layout of antenna presence test using GPIOs
