Newbie and first thoughts

Discuss KerberosSDR - 4x Coherent RTL-SDR
Tom_G0JSV
Posts: 16
Joined: Tue Feb 11, 2020 6:51 pm

Newbie and first thoughts

Post by Tom_G0JSV » Tue Feb 11, 2020 7:37 pm

My KerberosSDR arrived a couple of days ago and I am getting to grips with it. Initially I had a few issues and like lots of the other posts in this forum these were related to power or rather the lack of it. I am using a RPi 4 with the latest 1.5 image. At first, I thought I could power the KerberosSDR from the RPi (using the Blue USB 3 connections) but have since discovered that everything seems to work much better if the Kerberos is started firstly using its own PSU followed by the RPi.

I don't have any Android gadgets to hand so currently using the 2 web applications from an Apple phone.

Internal Hotspot Address for Web Control: IP_ADDR:8080/init
Internal Hotspot Address for Android App: IP_ADDR:8081

Plus Real VNC from a Windows PC when needed.

I do own a traditional doppler DF system but the phase technology offered by the Kerberos is at the next level. Even when just looking at the graphs on the configuration software you can see how the unit acquires a signal and locks onto it.

The re-configuring needed at every restart/freq change is a bit of a pain. I did read about the intention to add antenna switches so that the antennas could be dis-connected/re-connected automatically. I did wonder if this could be accomplished partly in software. i.e. connect the 4 dummy loads, configure and then store that state.

Anyway, early days. A lot to learn.

Tom.

P.S. Could a Nextion screen be driven from the data that drives the web based compass I wonder ?

Tom_G0JSV
Posts: 16
Joined: Tue Feb 11, 2020 6:51 pm

Re: Newbie and first thoughts

Post by Tom_G0JSV » Wed Feb 12, 2020 2:55 pm

I spotted a small python script in the /kerberos/_webDisplay directory.

This looked like a good candidate to test an output to a Nextion screen. The file is called DOA_res_write.py

Looks like a test script that has a random counter going up to 360. It reads from a html file called /ram/DOA_value.html and writes the latest value back to the same.

Connected up the Nextion which had a simple application created consisting of one page and 2 text-boxes.

It only worked.

The modified, very simple proof of concept script is shown below;

# -*- coding: utf-8 -*-

import serial
import time
import numpy as np

port=serial.Serial(port='/dev/ttyAMA0',baudrate=9600, timeout=1.0)
endline = "\xff\xff\xff"
page = 0
pic = 0
dimScreen = "dim=0"
undimScreen = "dim=80"
port.write("page 0" + endline)
port.write(undimScreen + endline)

fd = open("/ram/DOA_value.html","w")
for i in range(360):
DOA = int(i+np.random.normal(0,3))
DOA_str = str(DOA)
DOA_str += ' ' * (4-len(DOA_str))
html_str = "<DOA>"+DOA_str+"</DOA>"
fd.seek(0)
fd.write(html_str)
print(html_str)
time.sleep(0.2)
fd.close()

txtObj001 = 'page0.txt001.txt="'+DOA_str+'"'+endline
txtObj002 = 'page0.txt002.txt="'+html_str+'"'+endline
port.write(txtObj001)
port.write(txtObj002)
Attachments
Pic.jpg
Nextion
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ckoval7
Posts: 21
Joined: Fri Sep 27, 2019 8:54 pm

Re: Newbie and first thoughts

Post by ckoval7 » Wed Feb 12, 2020 4:24 pm

I don't really know anything about those displays. Can you just make them pull a webpage?

Tom_G0JSV
Posts: 16
Joined: Tue Feb 11, 2020 6:51 pm

Re: Newbie and first thoughts

Post by Tom_G0JSV » Wed Feb 12, 2020 4:55 pm

Hello,

Firstly a disclaimer. I have nothing to do with Nextion but recently have started to play around with Nextion screens as they are often an option with amateur radio hot-spots.

A Nextion screen is not a monitor for the computer. So if you connect one to a RPi you will not see the typical Raspbian boot/start-up screens. e.g. The rainbow pattern followed by all the devices loading followed by the desktop.

Instead, it typically interfaces with an application (app) on the RPi (or other device) and uses an API that has been implemented as part of the app. Sounds complex? it isn't. The code above shows just how simple the API can be. A few extra lines added to an existing script.

The Nextion behaves like an Arduino. You build a script and upload it to the Nextion. It typically loops around the script to populate objects such as a textbox. But it has complex objects too such as sliders/gauges etc.

So in the example provided, I piggybacked onto an existing bit of Python code and extended it to grab some data and populate a couple of objects on the Nextion screen.

I need to dash now but will put another post together later or tomorrow with some more info.

Tom.

rtlsdrblog
Site Admin
Posts: 2521
Joined: Mon Nov 19, 2012 11:54 pm

Re: Newbie and first thoughts

Post by rtlsdrblog » Thu Feb 13, 2020 2:49 am

Tom_G0JSV wrote:
Tue Feb 11, 2020 7:37 pm
My KerberosSDR arrived a couple of days ago and I am getting to grips with it. Initially I had a few issues and like lots of the other posts in this forum these were related to power or rather the lack of it. I am using a RPi 4 with the latest 1.5 image. At first, I thought I could power the KerberosSDR from the RPi (using the Blue USB 3 connections) but have since discovered that everything seems to work much better if the Kerberos is started firstly using its own PSU followed by the RPi.
Yep definitely best to power it via a second supply if using on a SBC. The Pi 4 simply can't provide enough current for the four radios through it's USB port.
Tom_G0JSV wrote:
Tue Feb 11, 2020 7:37 pm
The re-configuring needed at every restart/freq change is a bit of a pain. I did read about the intention to add antenna switches so that the antennas could be dis-connected/re-connected automatically. I did wonder if this could be accomplished partly in software. i.e. connect the 4 dummy loads, configure and then store that state.
Saving the config is not possible, because everytime the tuners are turned on or retuned the phase shifts inside are completely random. So you'd be saving an incorrect state for the next tuning/power cycle.

The hardware switches should solve this manual work problem.

Hope that you'll continue to have fun with it! New software updates that should be quite interesting are in the works for this year, so some exciting developments are on the way.

Tom_G0JSV
Posts: 16
Joined: Tue Feb 11, 2020 6:51 pm

Re: Newbie and first thoughts

Post by Tom_G0JSV » Thu Feb 13, 2020 9:10 pm

Thanks for the info re-power. Plus the explanation regarding the initial config.

I lost half a day today because I just could not get the KerberosSDR to go blue (i.e. the internal lights). The White light came on but no matter what I did the blue lights didn't shine. I tried another USB cable, and then another, and yet another. No joy. I was about to give up but then remembered that the working cable had a logo on the fat end. I had re-purposed that cable for another job. Found it, plugged it in and the blue lights came on again. Phew. The logo isn't important but that cable was obviously very different from the 3 substitutes. Assume that they were all designed for charging as opposed to data TX.

Can you recommend a good cable? Maybe include one for a small fee with any new orders?

Still having a few issues on the networking side. It is all a bit hit and miss. If the RPi is plugged in to an Ethernet connection (I know...completely different network) I have more success. The RPi can be reached using WiFi to the internal access point. [@ 192.168.4.1]. But if the physical cable isn't connected the VNC software nor the Web pages will respond.

The connection to the 'hotspot' is good because using a network analyser both IP addresses are visible. Host and a single client.

But if the physical cable isn't connected, the hotspot will accept a connection but nothing else will work.


Tom.

Tom_G0JSV
Posts: 16
Joined: Tue Feb 11, 2020 6:51 pm

Re: Newbie and first thoughts

Post by Tom_G0JSV » Thu Feb 13, 2020 9:40 pm

On a positive note.

I tuned into the Airband frequencies. This isn't a regular playground for me but some constant traffic was needed for testing and this fitted the bill.

The receiver was connected to a white stick on the roof of the house (@12M) and the Kerberos was plugged into 4 aerials at knee height (@0.30 M).

There was a lot of traffic heard on the receiver but every now and again there was plane that was picked up on the 4 DF aerials. These resulted in a very steady bearing on the html compass app.

Tom.

Tom_G0JSV
Posts: 16
Joined: Tue Feb 11, 2020 6:51 pm

Re: Newbie and first thoughts

Post by Tom_G0JSV » Fri Feb 14, 2020 2:37 pm

This mock-up is reading data from a modified static copy of the compass.html file. Next is to see if it can keep up with a live version of the file!!
LatestPic.jpg
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Tom_G0JSV
Posts: 16
Joined: Tue Feb 11, 2020 6:51 pm

Re: Newbie and first thoughts

Post by Tom_G0JSV » Fri Feb 14, 2020 3:24 pm

Correction, the live content I need is actually in the /ram/DOA_value.html file and not in the compass.html. That will make things easier. Done that already.

Tom_G0JSV
Posts: 16
Joined: Tue Feb 11, 2020 6:51 pm

Re: Newbie and first thoughts

Post by Tom_G0JSV » Fri Feb 14, 2020 4:45 pm

Almost there. The stats are updating every second from the live source file now. This refresh rate seems adequate. I did try 200ms but that is probably unnecessary. Next I will strip those XML headers and move on to the compass after that.
Pic1.jpg
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