The following parameters are needed to configure antenna switching.
| Setting | Description |
|---|---|
| TSWITCHSPACING | This setting is the interval between every time the antenna is changed in the switching state. |
| TSWITCHOFFSET | This setting lets you fine-tune the switching instant (e.g., if an external antenna switch has a long switch delay). |
| DFEGPIO[n] (n=0..7) | This setting configures the GPIOs used in switching antennas, determined by the SWITCHPATTERN setting. |
| SWITCHPATTERN | Writing adds a GPIO configuration to the switching pattern to be used. Each configuration contains 8 bits, one for each GPIO, where bit 0 indicates DFEGPIO[0], bit 1 indicates DFEGPIO[1] and so on. A switch pattern is generated by writing multiple configurations consecutively to SWITCHPATTERN. The first configuration is used in the data part of the packet, the second configuration is used in the guard and REFERENCE periods, and each subsequent configuration is applied at the beginning of the next switch slot. |
The GPIOs must be configured as outputs in the GPIO peripheral (e.g. with the DIRSET register) in addition to the DFEGPIO register. The radio only controls these GPIOs while it is enabled, so to avoid uncontrolled toggling of these GPIOs it is recommended to set configuration 1 as default output for these GPIOs (e.g. using the OUT register in the GPIO peripheral).
When the last switch pattern is reached and IQ sampling continues, the switch pattern loops back to the one used in the first SWITCH slot. The following diagram shows five antenna patterns that have been loaded.
Figure 1. Antenna switching
