This section describes, how the LQI value is retrieved. LQI stands for "link quality indication" and is a measure for the quality of a received frame. The LQI measurement is an average correlation value of multiple symbols that is calculated for each received packet. The implemented LQI does not reflect the received signal strength. Rather it is a measure of the signal distortion, e.g. due to multipath propagation. For a more detailed explanation refer to the AT86RF230 data sheet.
The range of the parameter is 0...255, where the value 0 is associated with a low signal quality, whereas the maximum value of 255 is associated with a high signal quality.
The LQI value is stored in the SRAM of the radio transceiver, directly behind the last byte of the received frame. It is valid 32 us after the interrupt TRX_IRQ_TRX_END.
The LQI value can be retrieved by one of the following methods:
This sequence shows, how the LQI value for a received frame is retrieved with the frame upload procedure. The frame upload function must not access the LQI value before 32 us after the TRX_IRQ_TRX_END interrupt.
- Code example
This sequence shows how the LQI value can be read from the SRAM. It can be used in the situation, where the 32 us delay between the TRX_IRQ_TRX_END interrupt and LQI availability have to be used for other tasks, e.g. for software based ACK frame generation. This method is e.g. usefull in combination with the software generated ACK frame processing (see PHY_DATA_INDICATION_FAST).
- Code example
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