RSSI

Purpose

• determine signal strength from different sources / GPIO pins

Considerations

• Need to keep functions generic for GPIOs

• What is providing the RSSI signal? What is the form of the data (Need to ask Aidan Bowers)

• Related hardware: An RC Link

  • RFD900.

    • https://files.rfdesign.com.au/Files/documents/Software manual.pdf

    • Need to see how RFD900 sends RSSI signals and how it interfaces with the actual flight controller. Then can determine what signal needs to be "decoded"

• Will the PPM driver be what calls the RSSI module?

  • (2021 year was PWM, this year 2022 will need to look into RFD900)

• We are no longer using singleton, need to get rid of that

• Functions:

  • Normalized and unnormalized function returning signal strength

  • Threshold function returning a bool representing ‘good signal' and bad signal, or a function returning one out of a scale of judgements, e.g. ‘no signal', ‘bad signal’, ’ok signal' , ‘good signal', 'strong signal’ represented as an integer

• For pull request:

  • Make LOS/RSSI branch (after weekend)

Research

• RSSI signal can come as analog or PWM

Ardupilot implementation

• RSSI.cpp calls on AnalopIn.cpp class for its ‘channel’ function

  • https://github.com/ArduPilot/ardupilot/blob/master/libraries/AP_RSSI/AP_RSSI.cpp

  • https://github.com/ArduPilot/ardupilot/blob/master/libraries/AP_HAL_SITL/AnalogIn.h

• AnalogIn.cpp has ‘channel’ function which returns a pointer to an AnalogSource object by calling the ADCSource object constructor

  • (ADCSource inherits from AnalogSource)

  • https://github.com/ArduPilot/ardupilot/blob/master/libraries/AP_HAL_SITL/AnalogIn.cpp

• AnalogSource is an abstract class, defines in a different AnalogIn file

  • https://github.com/ArduPilot/ardupilot/blob/master/libraries/AP_HAL/AnalogIn.h