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sheaivey / rx5808-pro-diversity

DIY project to create your own 5.8ghz FPV diversity basestation - based off the rx5808 receiver module. Project includes basic Arduino Nano implementation to advanced custom PCB board and introduction to digital switches 4066 chip.
http://www.laforgefpv.com
MIT License
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How are the RSSI Values created? #153

Open swatza opened 6 years ago

swatza commented 6 years ago

I was trying to dig through the code as I am using this as a low cost sensor for some RF research to figure out what the outputted value represents. The best guess I have is that its an RCPI 8bit between 0-220 (as comments I found indicated min values were 90 and max were 220) but I am not sure if that mapping is correct.

Any information about the exact details would be helpful.

JyeSmith commented 6 years ago

In receiver.cpp you can see the analogRead function which reads the RSSI value.

The below link explains the returned value 😃

https://www.arduino.cc/en/Tutorial/AnalogInput

swatza commented 6 years ago

Okay, so if I am understanding this correctly: mapping 0-1023 from 90 to 220 or 0 to 100. Therefore 90 would equal 0 Volts and 220 should equal 5V or 100%.

JyeSmith commented 6 years ago

The RSSI min/max output range isn't from 0 to 5v, but more like 0.5 to 1.2. Hence the min and max calibration values are only ~90 to ~220.

The 0 to 100 conversion you see in the code is to normalise Rx modules on the same scale. It then makes it easy to see a 2% difference, which is the threshold for switching between the Rx modules.