66 lines
2.5 KiB
Markdown
66 lines
2.5 KiB
Markdown
# RSSI
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RSSI is a measurement of signal strength and is very handy so you know when your aircraft is going out of range or if it is suffering RF interference.
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Some receivers have RSSI outputs. 3 types are supported.
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1. RSSI via PPM channel
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1. RSSI via Parallel PWM channel
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1. RSSI via ADC with PPM RC that has an RSSI output - aka RSSI ADC
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## RSSI via PPM
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Configure your receiver to output RSSI on a spare channel, then select the channel used via the CLI.
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e.g. if you used channel 9 then you would set:
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```
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set rssi_channel = 9
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```
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Note: Some systems such as EZUHF invert the RSSI ( 0 = Full signal / 100 = Lost signal). To correct this problem you can invert the channel input so you will get a correct reading by using command:
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```
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set rssi_invert = ON
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```
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Default is set to "OFF" for normal operation ( 100 = Full signal / 0 = Lost signal).
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## RSSI via Parallel PWM channel
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Connect the RSSI signal to any PWM input channel then set the RSSI channel as you would for RSSI via PPM
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## RSSI from Futaba S.Bus receiver
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The S.Bus serial protocol includes detection of dropped frames. These may be monitored and reported as RSSI by using the following command.
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```
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set rssi_src_frame_errors = ON
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```
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Note that RSSI stands for Received Signal Strength Indicator; the detection of S.Bus dropped frames is really a signal quality, not strength indication. Consequently you may experience a more rapid drop in reported RSSI at the extremes of range when using this facility than when using RSSI reporting signal strength.
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## RSSI ADC
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Connect the RSSI signal to the RC2/CH2 input. The signal must be between 0v and 3.3v.
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Use inline resistors to lower voltage if required; inline smoothing capacitors may also help.
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A simple PPM->RSSI conditioner can easily be made. See the PPM-RSSI conditioning.pdf for details.
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Under CLI :
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- enable using the RSSI_ADC feature : `feature RSSI_ADC`
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- set the RSSI_SCALE parameter (between 1 and 255) to adjust RSSI level according to your configuration. The raw ADC value is divided by the value of this parameter.
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Note: Some systems invert the RSSI ( 0 = Full signal / 100 = Lost signal). To correct this problem you can invert the input so you will get a correct reading by using command:
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```
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set rssi_invert = ON
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```
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## RSSI_SCALE setup method:
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- set rssi_scale = 100. The displayed percentage will then be the raw ADC value.
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- turn on RX (close to board). RSSI value should vary a little.
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- Update rssi_scale to the maximum RSSI value previously measured.
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FrSky D4R-II and X8R supported.
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The feature can not be used when RX_PARALLEL_PWM is enabled.
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