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LR11XX Spectrum Display example

Description

The application implements Spectrum-Display operation by setting the device in Rx continuous mode and regularly reading instantaneous RSSI one frequency channel after the other. The spectrum covering all the channels being scanned will be plot on terminal screen. From the start channel frequency, defined by FREQ_START_HZ, 1 sample point of RSSI level will be fetched for every frequency channel by using GetRssiInst function. After collection of all frequency channel RSSI values, a spectrum curve is drawn on terminal screen. This curve will be refreshed every PACE_S second(s) by repeating the processes done before.

Here is an example of the curve will be displayed on terminal screen. The bottom of the curve represents noise floor around the antenna in frequency band being scanned. The spikes represent which frequency channels have RF activity happening. The frequency frame displayed below x-axis is the frequency band being scanned. Y-axis indicates for RSSI level.

    ^
   0|
  -4|
  -8|
 -12|
 -16|
    .
    .
    .
 -76|
 -80|                          _
 -84|                    _    | |
 -88|                  _| |   | |
 -92|_                |   |   | |              _
 -96| |               |   |   | |             | |              _
-100| |               |   |   | |             | |             |
-104| |            _  |   |_._| |_     _     _| |             |
-108| |_._._._._._| |_|           |_._| |_._|   |_._._._._._._|
-112|
-116|
-120|
-124|
-128|
/dBmx------------------------------------------------------------>
     2400 --> 2406 MHz

The plotting function is supported by VT100 control code. So, to run this demo normally, a terminal like Tera Term supporting VT100 control code is necessary.

The sample code will be used to perform test under both LoRa and FSK modem tests, but there should be no difference if the band-width is the same. Define macro PACKET_TYPE to LR11XX_RADIO_PKT_TYPE_LORA or LR11XX_RADIO_PKT_TYPE_GFSK (in file ../../common/apps_configuration.h) to enable each modem in the test.

Configuration

Several parameters can be updated in ../../common/apps_configuration.h header file:

Constant Comments
PACKET_TYPE Set the modem will be used
LORA_BANDWIDTH BandWidth of LoRa packets
FSK_BANDWIDTH BandWidth for GFSK packets

Several parameters can be updated in main_spectrum_display.h header file:

Constant Comments
FREQ_START_HZ First channel frequency to do the scan
NB_CHAN Number of channels need to scan
PACE_S Number of seconds between 2 scans in the thread
WIDTH_CHAN_HZ Width between each channel
RSSI_TOP_LEVEL_DBM Highest RSSI value, default: 0dBm
RSSI_BOTTOM_LEVEL_DBM Lowest RSSI value, default: -128dBm
RSSI_SCALE RSSI scale for Spectrum-Display display