Update on T-Echo with SoftRF as a FLARM Installation Test Receiver

[Neil Allison]

Hello,

Thank you Moshe for the changes you made to collect RSSI in the range.txt file and display the maximum RSSI on the T-Echo Traffic details page and Time page.  

I  found those pages a little slow to update when using the T-Echo to "sniff" around the outside of a glider cockpit to check an antenna installation so I dug out my changes that display RF_last_rssi in the middle right (navbox4) of the Status page and applied it to a fork of MB162.  

In my informal tests I observed that this RF_last_rssi value is updated every second (or so) while the max RSSI displays can take some time to update, especially when the signal is reducing.   I found the faster update more useful for this investigation measurement activity.  The navboxes have larger text so that is easier for my, ahem, older eyes.

With the new season starting in NZ, I am expecting renewed enthusiasm to check FLARM installations on the ground and so I've bought a second T-Echo to loan or use for that purpose.

In case it is of any use to anyone, I put the source and a Zip file containing the compiled UF2 / Zip file in Github:

https://github.com/nallison/SoftRF/tree/dev_RSSI_MB162.  On the boot page the software version is displayed as RS162. 

Safe flying,

Neil.

[Moshe Braner]

Thanks Neil.  But I'd rather figure out why the RSSI display in the two places I put it does not refresh often enough.  A quick look at the code says that the max-RSSI displayed on the Time screen should be once per second.  Is that too slow?  Or does it appear to happen less often than that?

[Neil Allison]

I agree that the display updates every second.  

In my brief search through the code, it appears that the value of maxrssi appears to be a "quasi-peak detector" where it updates with the most recent maximum, probably every second, but I did not find the logic that drives the  "decays" or time-out for setting to a lower value or RSSI.  From my searching and testing I think the RF_last_rssi is indeed the latest value and not subject to any peak detect or filtering.

Updates every second are suitable but I'm too impatient to wait several seconds for an updated reading.

-- 

Neil

[Moshe Braner]

The variable "maxrssi" is intended for a totally different purpose, regarding the collection of statistics about RSSI vs. distance for ADS-B signals.  On a T-Beam only.

In the traffic page on the EPD display of the T-Echo, the RSSI is displayed by the function EPD_Draw_Text() and it uses fop->rssi (the latest), not fop->maxrssi.  That should be correct.  But you have to get to that page, and then to the correct aircraft if more than one is being tracked.

In the function Traffic_Count() the variable "maxrssi" is used for a different purpose, the (latest) RSSI of the tracked non-ADS-B target that was received with the strongest ("maximum") signal.  The idea is that as you walk around the glider measuring the RSSI, you don't want to see the RSSI of some glider flying overhead (or across the airport).  That is what I intended to display in the time page on the T-Echo.  As the comment in EPD_time_loop() says: "// show the latest max RSSI"  But it comes from the "maxrssi" variable.  On a T-Echo that should still be correct since there is no ADS-B reception?  But I should split those two things into separate variables.

So I do see a bug now, but I don't see how it would make that display wrong or slow?  :-)

[Moshe Braner]

Actually the global var "maxrssi" is ONLY set in Traffic_Count().  The ADS-B stats just use the maxrssi field within the traffic struct.  So not a bug.  And I still don't see why refresh within the T-Echo display would be slow.  If anybody spots it let me know.

[Moshe Braner]

I now did the actual experiment.  T-Beam with SoftRF as the signal source.  T-Echo with my SoftRF showing the RSSI.  Walked with it to see the RSSI change.  Worked fine, updates every second.  Both on the time page and on the traffic details page.  Of course the RSSI is not very stable, and depends on where the T-Echo is relative to your body, etc.  But that's a separate issue.  On the T-Beam I made it report the RSSI on the OLED, but also in the status web page, so you can put the T-Beam on the ground or something, and walk some distance away and read the RSSI on your phone.