LQI of Received Frames

This section describes, how the LQI ("link quality indication") value can be retrieved. The LQI value is a measure of the signal quality of a received frame, using correlation results of multiple symbols during detection. The range of the LQI value is 0...255, where the value 0 is associated with a low signal quality (leading almost always to a frame error), and the maximum value 255 is associated with a high signal quality (leading almost always to a correctly received frame). For a more detailed explanation on the conditional frame error rate, when receiving a certain LQI value, refer to the AT86RF231 datasheet.

The LQI value can be retrieved by one of the following methods:

• PHY_GET_FRAME_LQI
• PHY_GET_SRAM_LQI

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PHY_GET_FRAME_LQI

This sequence shows how the LQI value for a received frame is retrieved with the frame read procedure. The frame read function must not access the LQI value before the TRX_IRQ_TRX_END interrupt.

Code example

    /* AT86RF231::[RX_BUSY] */
    /* TRX_IRQ_TRX_END occurs here */
    /* AT86RF231::[RX_ACTIVE] */
    frm = trx_frame_read();
    flen = frm[0];
    lqi = frm[flen];

PHY_GET_SRAM_LQI

This sequence shows how the LQI value can be read from the SRAM. This method is e.g. useful in combination with the software generated ACK frame processing (see PHY_DATA_INDICATION_FAST).

Note:

The LQI is valid till the reception of the SFD of the next incoming frame.

Code example

    /* AT86RF231::[RX_BUSY] */
    /* TRX_IRQ_TRX_END occurs here */
    /* AT86RF231::[RX_ACTIVE] */
    flen = trx_frame_length_read();
    trx_sram_read(flen, 1, lqi);

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