CC2530 RSSI OFFSET

pengling ren

Prodigy 110 points

Other Parts Discussed in Thread: Z-STACK

CC2530de RSSI值怎么获取？

利用int8 rssi;
rssi = pkt->rssi;得到的rssi，需要减去73才是真实的RSSI值吗？pkt里的rssi与RSSI寄存器的值为什么不一样，而且有20左右的差距，它俩之间有什么公式可以互算吗？有什么区别？

12 年多前

0 Yue TANG 12 年多前

TI__Mastermind 39047 points

看如下这篇文档。

http://www.ti.com/lit/an/swra114d/swra114d.pdf

3 RSSI Register Interpretation
The RSSI value read from the RSSI status register is a 2’s complement number and is in
dBm with ½ dB resolution. The following procedure can be used to convert the RSSI reading to an absolute power level (RSSI_dBm).
Assume that the RSSI offset is 72 dB and that 11111010b is read from the RSSIregister.
If 11111010b is interpret as a 2’s complement number it has the value -6.This means that the RSSI value, before taking the offset into account, is -3 dBm. Subtracting the RSSI offset, the RSSI value in dBm ends up at -3 dBm - 72 dB = -75 dBm.

0 pengling ren 12 年多前回复 Yue TANG

Prodigy 110 points

谢谢你，但是这里面不包括ＣＣ２５３０，我看过datasheet。里面说offset是－73.在1米处从pkt－＞rssi，得到的rssi是D3，它是带符号二进制的，怎么求出rssi的真实值呢？？

0 Yue TANG 12 年多前回复 pengling ren

TI__Mastermind 39047 points

To find the actual signal power P at the RF pins with reasonable accuracy, an offset must be added to the
RSSI value. P = RSSI – OFFSET [dBm]
For example, with an offset of 73 dB, reading an RSSI value of –10 from the RSSI register means that the
RF input power is approximately –83 dBm. For the correct offset value to use, see the data sheet。

datasheet中offset为

我不知道你的PKT->RSSI是哪里的。在z-stack里你可以看到如下，我估计D3应该是已经通过计算后的了，表示RF input power 大概是为D3-FF= -45dbm, 一米差不多。

/* record link quality metrics for the receive ACK */
      {
        int8 rssiDbm;
        uint8 corr;

        rssiDbm = PROPRIETARY_FCS_RSSI(fcsBuf) + MAC_RADIO_RSSI_OFFSET;
        MAC_RADIO_RSSI_LNA_OFFSET(rssiDbm);
        corr = PROPRIETARY_FCS_CORRELATION_VALUE(fcsBuf);

        pMacDataTx->internal.mpduLinkQuality = macRadioComputeLQI(rssiDbm, corr);
        pMacDataTx->internal.correlation = corr;
        pMacDataTx->internal.rssi= rssiDbm;
      }