From aae0c1e888d173b7a850a3e0023b8c352f657f62 Mon Sep 17 00:00:00 2001 From: patacongo Date: Fri, 19 Aug 2011 16:51:04 +0000 Subject: Add support for multiplexed SDIO pins from Uros git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@3898 42af7a65-404d-4744-a932-0658087f49c3 --- nuttx/drivers/wireless/cc1101/cc1101.c | 39 ++++++++++++++++++++++++++++++++++ 1 file changed, 39 insertions(+) (limited to 'nuttx/drivers/wireless') diff --git a/nuttx/drivers/wireless/cc1101/cc1101.c b/nuttx/drivers/wireless/cc1101/cc1101.c index e2fae9620..a35575690 100755 --- a/nuttx/drivers/wireless/cc1101/cc1101.c +++ b/nuttx/drivers/wireless/cc1101/cc1101.c @@ -55,6 +55,45 @@ * - Power up/down modes * - Sequencing between states or add protection for correct termination of * various different state (so that CC1101 does not block in case of improper use) + * + * \par RSSI and LQI value interpretation + * + * The LQI can be read from the LQI status register or it can be appended + * to the received packet in the RX FIFO. LQI is a metric of the current + * quality of the received signal. The LQI gives an estimate of how easily + * a received signal can be demodulated by accumulating the magnitude of + * the error between ideal constellations and the received signal over + * the 64 symbols immediately following the sync word. LQI is best used + * as a relative measurement of the link quality (a high value indicates + * a better link than what a low value does), since the value is dependent + * on the modulation format. + * + * To simplify: If the received modulation is FSK or GFSK, the receiver + * will measure the frequency of each "bit" and compare it with the + * expected frequency based on the channel frequency and the deviation + * and the measured frequency offset. If other modulations are used, the + * error of the modulated parameter (frequency for FSK/GFSK, phase for + * MSK, amplitude for ASK etc) will be measured against the expected + * ideal value + * + * RSSI (Received Signal Strength Indicator) is a signal strength + * indication. It does not care about the "quality" or "correctness" of + * the signal. LQI does not care about the actual signal strength, but + * the signal quality often is linked to signal strength. This is because + * a strong signal is likely to be less affected by noise and thus will + * be seen as "cleaner" or more "correct" by the receiver. + * + * There are four to five "extreme cases" that can be used to illustrate + * how RSSI and LQI work: + * 1. A weak signal in the presence of noise may give low RSSI and low LQI. + * 2. A weak signal in "total" absence of noise may give low RSSI and high LQI. + * 3. Strong noise (usually coming from an interferer) may give high RSSI and low LQI. + * 4. A strong signal without much noise may give high RSSI and high LQI. + * 5. A very strong signal that causes the receiver to saturate may give + * high RSSI and low LQI. + * + * Note that both RSSI and LQI are best used as relative measurements since + * the values are dependent on the modulation format. **/ #include -- cgit v1.2.3