How to obtain RSSI

Hello All,

Is there any sample program that obtains RSSI? If not, could anyone please explain how I can obtain RSSI(Basically which register values I need to look into and the equation to obtain RSSI).

Thanks
Auvi

You can calculate an estimate of both the first path signal power and the total signal power based on the values of several registers and the current operating mode.
Section 4.7.1 and 4.7.2 of the DW1000 user manual gives the registers and calculations to use.

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Hi @AndyA , thanks a lot for your prompt reply. What is the difference between first path signal power and total signal power? Which one I’ll have to use to obtain the RSSI?

Which is better depends a bit on what you are doing.

Imagine that the UWB signal is transmitted as a single short pulse.

That pulse travels to the receiver in several ways. It travels in a straight line between the antennas but some of it also bounces off the floor, some bounces off walls and other objects. All of these reflections will travel a greater distance than the direct signal but depending on what they are reflecting off and how they combine could end up being just as strong or stronger at the receiver than the direct signal.

This means that at the receiver instead of seeing a single short pulse that we would like to get we receive an initial pulse (the direct signal has the shortest distance to travel and so always arrives first) followed by lots of other pulses of varying size as the reflections arrive.
If you plot the CIR values from the receiver (see the user manual and other posts here as to how) then you can effectively see a chart of this receive power over time. In an open field it’s a single spike, in a big metal room it’s horrible mess of spikes that combine to look like constant noise after the initial signal.

The first path power is an estimate of the power in that initial direct path signal, the total power is the power of the direct signal plus all the reflections.

For range measurements the direct path is the critical part, that is what you want to measure the time of to calculate any distances. So for timing related measurements that would be a better RSSI number. For data you don’t care so much about the timing accuracy and so total power may be more appropriate. As one of the app notes indicates you can also gain information by comparing the two, if they are similar then you have a good clear direct path without a lot of reflections, if the total power is a lot higher than the first path power then your direct antenna to antenna path could be blocked and the range measurements may not be very accurate.

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Thanks a lot for the explanation.