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Thursday, 14 October 2021

RASPAD3



 

 Will turn this into SDR thing tomorrow. 

I compiled the SDR++ and GQRX for the RaPi4 yesterday.


Wednesday, 13 October 2021

Installing GQRX and SDR++ on RaspberryPi

 Installing GQRX and SDR++ on RaspberryPi

These are all the steps I actually performed.

sudo apt update
apt list --upgradable
sudo apt install gqrx-sdr
rtl_test -t
gqrx

So GQRX sort of worked...

So SDR++

Grab the source
git clone https://github.com/AlexandreRouma/SDRPlusPlus.git
ls
cd SDRPlusPlus
mkdir build
cd build/
cmake ..

so erroring as missing these packages....fftw3 glfw glew libvolk

so to install them...
sudo apt-get install freeglut3
sudo apt-get install freeglut3-dev
cmake ..
sudo apt install libglew-dev
cmake ..
sudo apt install glfw3
sudo apt install libglfw3-dev
cmake ..
sudo apt install libairspy-dev
cmake ..
sudo apt install libairspyhf-dev
cmake ..
sudo apt install libhackrf-dev
cmake ..
sudo apt install libsoapysdr-dev
cmake ..

libiio missing....so get that compile and install

cd
git clone https://github.com/analogdevicesinc/libiio.git
cd libiio/
cmake ./
See what errors are (there were some)
cat /home/pi/libiio/CMakeFiles/CMakeOutput.log

install more prerequisites some were already there so it ignores them (from an SDR pluto install doc)
sudo apt-get install libxml2 libxml2-dev bison flex libcdk5-dev cmake
sudo apt-get install libaio-dev libusb-1.0-0-dev libserialport-dev libxml2-dev libavahi-client-dev doxygen graphviz

Try the libiio build again
cmake ./
make all
sudo make install
Add the path bit
PATH=/usr/lib/:$PATH
check it is working iio_info

go back to SDR _++ again
cd ..
cd SDRPlusPlus/
cd build/
cmake ..

so more missing get and install them

cd
git clone https://github.com/analogdevicesinc/libad9361-iio.git
cd libad9361-iio
cmake ./
make
sudo make install
cd ~/SDRPlusPlus/build/
cmake ..

still more missing

wget http://www.music.mcgill.ca/~gary/rtaudio/release/rtaudio-5.1.0.tar.gz
mv rtaudio-5.1.0.tar.gz ~/Downloads/
cd
cd Downloads/
tar -zxvf rtaudio-5.1.0.tar.gz
cd rtaudio-5.1.0/
mkdir build && cd build
cmake ../
make
sudo make install

Back to SDR++
cd
cd SDRPlusPlus/build/
cmake ..
this time no errors
used N=4 as 4 cpu make -j 4
It maxed out the CPU for a few mins
sudo make install

That's it SDR++ and GQRX both installed

 

Yes I am sure much of the missing bits were listed in the prerequisties docs of both but we all read those don't we :-) Of course I had added the development environment to it as well. Mine has 128GB SD card (high endurance) and has a 3TB SSD attached which takes and stores backups, snapshots etc I use an adaptor as well so I don't have to insert the MiniSD card into the Pi.

Saturday, 9 October 2021

Panic.... "Cannot open access to console, the root account is locked."

Last weekend I built myself a nice Pi 4 system for the shack. Everything worked perfectly, but today as I rebooted the Pi would simply not boot up. Usually I run almost all my Pis in a headless configuration but as this is the desktop for the operating position I had monitors connected.
 Eek, there is was, there it was, The Pi would get stuck at boot with the following error message

"Cannot open access to console, the root account is locked."
The error message while not too descriptive, it asked me use sulogin and run journalctl -xb however there was no shell to run or list anything.

I thought oh no there goes the system will have to rebuild it. However, I thought I would investigate some more.

After some google work, I found the following workaround that worked for me. Note for those that try to do this themselves: You will need access to a display,keyboard and a laptop/desktop to do the following steps

Retrive your SD card from the Pi and using a adapter mount the card to your PC,Mac or Linux. I use a rocketek that takes either normal or small SD cards .You should be able to see the /boot partition of your SD card.
Locate the file fstab in the rootfs partition and edit out the usb drive I added in last time and left in place! You might need to sudo to root to write this file or the next one see later if that is the case....
Or find the bootfs and look for the cmdline.txt file and add the following at the end of the line init=/bin/sh Note: Do not create a new line, just add the above to end of the current line. This will make the system give you a prompt so you might be able to figure out what the problem is. A bit like one of the earlier linux installs.
Load the SD card back into the pi and boot up.
if you did the cmdline.txt change you should now get the a root shell prompt and I expect you will know how to fix it from there. You could undo the changes to /etc/fstab or whatever else that  might have caused an issue.
I found I could not make and save the changes to the files as the system will complain the SD card is read only file system. If you get that move to the next sections.

A raspberry pi SD card will has two main partitions, since we cannot read the partition table directly you must manually locate the device for your root and boot partitions. You can do this by going to the /dev directory and you should see something similar to mmcblk0p1 & mmcblk0p2. You could use ls -l to check.

Mine is:

brw-rw----  1 root disk    179,   0 Oct  8 18:28 mmcblk0

brw-rw----  1 root disk    179,   1 Oct  8 18:28 mmcblk0p1

brw-rw----  1 root disk    179,   2 Oct  8 18:28 mmcblk0p2

The second device mmcblk0p2 will be your root partition. You need to remount this with read write permissions

mount -o remount,rw /dev/mmcblk0p2 /
Once this is remounted, go ahead and edit your /etc/fstab and save it.

The offending line in mine was:

#/dev/sda1 /disk1 auto defaults 1 1

Before you exit, make sure you revert the change to the cmdline.txt in the /boot partition. You may need to mount that in read write mode as you did above for the /root partition before you can change it.

mount -o remount,rw /dev/mmcblk0p1 /boot

Alternatively you can revert back the change to cmdline.txt on your laptop as I did using the USB adapter.

If everything goes well, you should be able to boot back your Pi in a normal way.

Panic over

Tuesday, 3 August 2021

What to build with STM32F746G-Disco and SI5351 Board

I had these in the workshop and as not operating right now, thought what could I make with these and a few other RFy things from the 'junk box'.




Well I know  have some SA612 and SMD op amps and lots of SMD discretes so thought might try the EU1KY analyser, after looking at JA versions (but seemed to miss out on the kitting as was sorting Mum's stuff out for Dad).

The STM32F746G-DISCO board in a blister pack, with a H7 version too, has been in the junkbox for a bit.

I bought a couple of the Front end RF PCB a while back for the EU1KY.

I have a few SI5351 modules with 25MHz crystal so might see about just removing the chip from one and adding it to the PCB and reusing some of the SMA connectors and other components.




Monday, 12 July 2021

Shellinabox on RaspberryPi

It is definitely not new, and I claim no originality as this idea has been posted elsewhere before, but I mentioned in discussion that I was using this (along with octoprint) on my Raspberry Pi 'servers' used with the 3D printers and CNC between Cambridge and Cornwall, 400 miles (and when really remote on some DX trip, usually to tweak some SDR setting) to adjust stuff if needed. Sounded really useful so  I was asked could I provide some details:

So here goes (your mileage may vary so don't assume a pure cut and paste will work for you). There are plenty of albeit old guides out there that will help you set this up on full blown PC's.

First to make this super easy on myself I used the Debian "Buster" Raspberry Pi image. It should work with others but you might need to do some tweaking.

Shellinabox is self contained  and it does everything out of the box (no pun intended) over a single TCP port 4200 by default. You can change this and in fact you might want to if you are using it to access the server from outside the network.

The first thing is to install it...

As I mentioned I am using raspbian so this is super easy...

(assuming logged in as 'pi', I use apt myself but apt-get works)

sudo apt-get install shellinabox

That is it... simple hey. That gives you the default install. (The install started the service on mine too but /etc/init.d/shellinabox starts it! You might be able to use systemd systemctl etc... but I not tried)

You use it by using a web browser on a remote system and into the navigation window typing in the IP/or hostname if you have done some fancy networking of the the Raspberry Pi and then :4200 e.g. https://192.168.0.100:4200

You will get a plain white screen and a prompt to login will appear. Continue as you would normally. it is a CLI or shell s don't expect some GUI anything to work (it might but I never tried)

If it doesn't work visit https://code.google.com/archive/p/shellinabox/ this was 'abandoned' a few years ago there is a more recent fork at https://github.com/shellinabox/shellinabox you should find any further answers there including configuring it.

If you are running one of the paranoid browsers it might moan about an SSL cert, you can add one to remove this warning if wanted. Installing SSL Certs is beyond this post.

If you are intending to connect to this from outside your network you will need to a do a few things.

1. Secure the Raspberry Pi server (make sure everything is up to date, make sure the users are using decent passwords.) I use strong passwords and I added MFA. Google for it.

2. Secure the Raspberry Pi server (check you really have done it!)

3. Adjust the config so you are using either a different port to 4200 and make your router forward any requests for that port to it. Care!!! You are exposing YOUR network, don't do it if you don't know what you are doing or don't accept all the risks. There are loads of bored script kiddies out there 24x7x365 just waiting to find any exploit.

I use XTERM on my Linux desktop so I like it so I added some extra bits.... as didn't like the black on white. I use a black background and green letters which I also made a bit bigger. You can add lots of other bits and pieces the choices are up to you. (I add a login screen, tweaked MOTD, to remind you are connecting to a remote system).

The configuration is in /etc/shellinabox and /etc/default/shellinabox as CSS style sheets so it isn't too hard to tweak it. /etc/shellinabox/options-enabled is the file it uses, you can eiter edit a file directly or create one and link to it (probably better if you want to tweak it).

(I'll add some images, screen grabs to this post.)


Saturday, 30 January 2021

AC unit replacement.


Looks like AC has failed in shack so neither cools or heats now.


Right now operating without any heat in shack is a tad uncomfortable after a while.


The AC unit is an old eIQ-12WMINV the original gas was replaced with a new refrigerant a while back. Anyway the comms from the inner and outer have failed so time to get a new one. Done that but now it seems that the local AC guys that installed the previous one will not install this one as they didn't supply it, and as not prepared to pay a 150% mark up for the same unit just because they order it so a bit stuck or am I?


This is <7KG of R290 so doesn't actually need you to use an AC company. Not sure that is the wisest option but it looks like the locals have given me have no option but to commission this myself.


Why would I even think of doing this?

After recharging my dad's car AC and knowing all the kit still exists and having worked with gas lines, pumps and gauges and CFC's when I did my PhD for years I thought why should I not try and DIY this?


I got lots of hints and suggestions from others with similar units and this is what this post is about.


I have this kind of manifold gauge.




So worked out this much...In summary, inside unit is charged with nitrogen. Outside with refrigerant. So let the nitrogen out, connect the pipes. Then vacuum the whole lot inside and connect the outside.


These units are all supplied with refrigerant contained in the outdoor unit, so as long as don't open that it stays there.

 

You need to purge the other pipework of all the air. I have a vacuum pump to do this first down to about -30 PSI. Once done and connected up, and tested there are no leaks in the pipework, will do this two ways, one see that the unit holds the vacuum for a while and second to pressurise it with N2 as well and monitor the pressure levels on both occasions, open the outside unit gas line (containing the condenser), with the AC unit turned on and set to cool that will then draw/fill the gas lines with refrigerant and the AC unit will then work as planned.


I was told that without a pump and specialist A/C kit as this is new it is still possible to connect things up but you can risk losing too much refrigerant. If you do that you will probably need an A/C engineer to refill your unit properly. Think lots of costs.


However, it is not impossible, definitely not recommended but if no other options and if you are prepared to risk this the steps might be these. With the inner unit set to run cool then once you have tightened up all the joints fully on the gas lines then use a 1 second fill from the liquid valve with refrigerant, that is open the valve, having first got ready with leak spray or soapy water and a brush. You need to test all your joints several times with spray and listen and look for a serious leak. You might need to repeat a few times if you do find a leak but when satisfied with all of the joints you need to work out carefully the path of the refrigerant from the outdoor unit, through the indoor unit and back to the outdoor unit . The end of this is the T shaped valve on the outdoor unit. Take off the plastic cap on the T to reveal the schrader valve. Open the liquid valve for an other 3 seconds (you must hear the system filling up for 3 seconds) Close it and leak test the joints again.

Then with both valves closed, press in the schrader valve to expel air and refrigerant for 5 seconds. You will possibly see some oil deposits and aget a cold blast. The pipework is now full of refrigerant in gaseous form. Now open both valves fully and replace the purge cap. The system should now work.


However, this is a warning.......not using an Fgas engineer will invalidate the long term warranty of the unit and if it all goes wrong you will have to call one in anyway.....not cheap if they will even look at DIY units with R290 refrigerant (which is basically refined Propane so very flammable!). There is a very very real chance this could all go badly wrong with R290 as this ia a refined version of the same stuff you will find in camping gas and the AC unit has aboiut the same as two of those small cans so the result could be very bad. This is perhaps why the non technically minded, those without any tools should probably not even attempt this and go with an FGas engineer.


Anyway waiting for a period of drier weather and will go through the process.

(and I guess any comments to pick up if I had missed anything)

Saturday, 16 January 2021

New 13cm pipe end cap filter

Components RG402 semi rigid, piece of FR4, SMA connectors, 3-22mm pip cutter (to score the shield before removal), Brass M3 nut and bolt (should be M4 but don't have to hand).

Holes are 3mm (initially, filed out to have a tight fit about RG402 sheath. 16mm apart.

It's a 1" copper end cap. So much larger than the 10GHz ones you might have seen using the 1/2"/13mm end caps. But the principal is the same.


The RG402 make up isn't hard.

You take one end and strip off the teflon insulator and trim the centre conductor to about 4mm and fit a pin over.



Then solder on the other part.







Then solder into the FR4 (the shield remains below). I'll trim the probes to about 8mm before filling the cap.

You then solder on the end cap, first soldering the brass nut on the central hole so the brass bolt can be screwed in and out and secured by the second nut, I might add a red locking liquid (nail varnish works if the XYL has some she will not miss!). You tune by advancing this bolt. The more you advance the higher in frequency the filter tunes.


The soldering of the brass nut and pipe end requires considerable heat, I have a small precision (bit of an oxymoron when talking about a blow torch!) blow torch I use this this work.



I will make up and add the NanoVNA 3GHz scan image here, basically when tuned it will allow the 2.4GHz signal to pass and block frequencies either side, like mixing products.