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Vocore + RTLSDR

Posted: Wed Jan 18, 2017 6:37 am
by fionnlagh
Hello there!

After my Vocore started collecting dust in my cupboard, I finally decided to mess around with it again.
So I've set up a Linux VM to compile the new firmware (My vocore was still running Barrier breaker..) and I've noticed that OpenWrt has a package called "RTLSDR".

Short info about RTLSDR: These are utilities to turn a rtl2832u-based DVB-T dongle into a software defined radio with a frequency range from ~25 MHz to 1.7 GHz, depending on the tuner.

I thought: Hell no, this won't work with this thing, because the Vocore has way lower specs than a raspberry pi and I don't have audio.. Meeh, let's give it a try.

So I've compiled it in and soldered a USB Port on the Vocore, installed the firmware and checked if the dongle is recognised properly. It worked!
Because my Vocore does not have audio output (No dock..) I gave it a try with rtl_tcp. I fired SDRsharp up on my computer, configured it to use rtl_tcp, 1.024 MSps and it just worked. I was able to listen to FM radio, pager signals and so on.. Although tuning to frequencies was a bit slow.
While playing around I also noticed that my Vocore was getting REALLY hot, so I've salvaged a little heat spreader from a spare router. Still the Vocore reaches 70°C.
After confirming everything works I've decided to directly solder the Vocore to the RTLSDR dongle and put rtl_tcp into the /etc/rc.local so it starts on boot.

I plugged my "Vocore-Dongle" into a USB charger and I was surprised that suddently the RTLSDR Dongle was not being recognised.
Problem was: Some chargers probably short the USB data pins or use resistors- that causes the the Vocore to stop recognising the dongle. After cutting the data wires on a short USB extension lead it worked again.

So what is the point of doing this whole thing?
Yes, I could've just plugged the RTLSDR Dongle into my PC directly, but I have problems with RFI from my power supplies and my flatscreen. By using the VoCore as a rtl_tcp server I am able to move the dongle far away from my noisy equipment.

The setup still has some bugs: sometimes the rtl_tcp server does not start correctly on boot (Probably a network issue. I need a proper init.d script...) and needs to be restarted. Sometimes (when tuning around too fast) the Vocore completely freezes and needs a restart.

Re: Vocore + RTLSDR

Posted: Thu Jan 19, 2017 11:41 am
by Vonger
Haha, not sure what it is, but looks awesome. :)