2.1 RSSI Usage

The UHF products offer a digital Radio Signal Strength Indicator (RSSI) sampling, including history data, via the built-in 16-byte SFIFO buffer. Use the RSSI to obtain the signal strength over the received message. It is important to know that the transceiver/receiver starts the RSSI sampling immediately with the start of the active phase (except for ATA5830(N) and ATA5780(N)). Depending on the scenario and configuration, the buffer might be filled with 16 RSSI samples from noise, before the system detects a FIFO overflow. Therefore, the recommendation is to set the FIFO buffer over/underflow error disable option in the EEPROM configuration. Otherwise, an error is triggered, including for an IRQ event (optional), if an overflow happens. The FIFO buffer is organized as a ring buffer. This results in getting the RSSI values from the RF message, as the noise values are overwritten. To get useful data in the RSSI buffer, set the sampling rate according to the RF signal characteristics. Divide the number of transferred bytes by 16, and set the next larger sample value for the RSSI update period in the service configuration to get the RSSI characteristics of the whole RF message. Apply the same calculation with the reduced number of bytes for the signal strength of the payload. If the “stay in RX after EOT” option is enabled (or applied), ensure that the SFIFO content is not overwritten.