Taking the Raspberry Pi 2 for a Test Drive with GNU Radio | Hacker News Reader

Taking the Raspberry Pi 2 for a Test Drive with GNU Radio

rs-online.com

147 pointsandyjohnson046 comments

This is one of the projects I had in mind for the RPi 2. I've already got the RTL-SDR stick and it works great on my workstation, but having it portable would be even better. I'm happy to see that the RPi 2 can handle the workload. It will be interesting to see if the Pi can also handle trunk tracking.

How does one handle portable power for a RPi2? Does a normal USB Power brick (as increasingly used to top up phones) suffice?

Yup, if it charges a phone it should power a Pi.

http://www.adafruit.com/products/1566 is sold specifically for this purpose, and it has some interesting notes about how it behaves (like output fluctuation when the battery is simultaneously charging and providing power) that might be worth noting. If all you do is run off a battery, then unhook the battery to charge it, you shouldn't have those sorts of issues.

Those are some very interesting notes, Adafruit excels again. Thanks for the link!

500mA and up will charge a phone (assuming you're not also doing power-intensive things on it), but you'll probably need 1-2A to power a Pi and a SDR reliably.

Ah, looks like power consumption west up. B+ listed 600 mA typ, 2B is 800. http://linuxgizmos.com/raspberry-pi-gets-quad-core-soc-keeps...

Yep! Plus the tuner card itself can use 200mA or so, and if you want to use any other USB accessories they'll be drawing power as well. I unfortunately have too much experience using "phone chargers" that had enough current to run it 90% of the time, but under hard load would cause enough voltage drop on the 5V rail to reboot the Pi.

No, a `normal USB Power brick´ doesn't suffice.

It has to reliably provide 5 volts and at least 700mA (depending on your Pi model and peripherals). The Pi is more sensible to the voltage than the amperage.

See http://elinux.org/RPi_VerifiedPeripherals#Power_adapters for reliable information about that.

The Raspberry Pi forums are filled with "90% of the time it's the power supply not up to the specs, please check the specs" messages for any power and `random crashes´ related problems.

Got my Pi 2 recently, and it's awesome how much snappier it runs. I've only used them to spin up game console emulator appliances so far. Would love to hear about projects among the HN crowd. I'd really like to use one for something more interesting!

I use my 1st gen Pi to monitor the temperature in my BBQ smoker and host a single page web application to display the data over wifi.

I haven't touched the project in a while, but with summer quickly approaching I think it's time.

I don't think I'll see much improvement using the Pi 2, but hey, it can't hurt to upgragde :)

I'm in the early stages of building an application that uses the camera module and OpenCV to recognise gestures and generate audio effects. Kind of head/hand operated synthesizer. Maybe hook-up a video projector and throw-in some video effects too.

Secondary objective is to renew my acquaintance with C/C++ after years of mainly using managed languages, and to learn modern language features.

I have a raspberry pi A I think it is, hooked up with the camera taking timelapses every day and automated posting to youtube. Gave me an excuse to play with ember for the frontend too -> http://timelapses.psdavey.com

Current project for the pi2 is hooking it up over a 3G modem for remote monitoring of a study site for a science friend of mind. I want to be able for her to send an SMS and for the PI to send back a picture. All the bits are in place, just need to make it nice!.

Love the pi - so much fun!

Nice timelapses! Is there a way to regulate the color settings of the camera?

Probably, the issue is that there's reflection of the double_ish_but_not_really_this_is_new_zealand glazed glass. Also, I take a ruthless approach to "fun" on small side projects and rather it works than is perfect. I did try putting a box around it but it wasn't really that workable as it sits in the corner of the lounge and I don't want it to be too bulky.

What sort of colour settings would you tweak?

p.s. if any other pi-timelapse people are out there, I would be quite keen at some point to open up the API so that you can post links to your videos too.. then we can have a google map to all the timelapses and it'd be just great! :D

p.p.s. did have fun using the python http://rhodesmill.org/pyephem/ to calculate the "Nautical Sunset - who knew?" so that it will properly adjust rather than the crude approach of a cron-job with a large enough bracket!

Love side projects :)

My wife's Hedgehog tweets how much he runs every night (https://twitter.com/runhedgie). Hooked up a RPi NoIR camera, so a video is included in the tweet as well. All the code is here: https://github.com/jlhonora/iot

This is great! Thanks for sharing, I just got a bird feeder, this will be a perfect starting point for shooting images.

Cool project! I guess that with the Pi2 you could do some basic image processing to detect changes and then decide which footage is interesting.

Awesome. What's in it for Antu? Or does he just like running on a treadmill? :) very cool.

I used my RPi to attempt to monitor the fermentation of my beer, by making use of a time-of-flight sensor attached to the Pi, to measure the displacement of a hydrometer - https://www.anfractuosity.com/projects/zymeter-simple/

I use a Pi 2 to run a simple intranet at my house that acts as a portal to various network services, a B that I'm using to experiment with hydroponics automation and exposing sensor data over a REST API, and a B+ that I hooked up to Adafruit's thermal printer to make a GitHub-webhook-powered printer that prints a physical ticket when the issue gets assigned to someone.

Have you published anything about your hydroponics automation? I'm fairly interested in eventually automating an aquaponic garden/farm with Pis.

I haven't yet, unfortunately the project has been on the backburner the last year or two since I've been so busy with other things. So far I've basically hooked up a relay board with an I2C GPIO extender, and use the Pi to toggle relays for lights and pumps. I also have an Arduino hooked up via serial that acts as an environment sensor, logging TDS, pH, light status (with a basic photoresistor, although this could be expanded to a fancy color temp sensor), and temp+humidity. It also monitors water level via a float switch. When the float switch is triggered, it adds more water. This naturally brings the TDS down, which triggers relays for peristaltic pumps to add a given ratio of nutrients.

The goal is to have a RESTful API service running on the Pi so that I could deploy one Pi+environment sensor setup per reservoir with a basic js app to monitor variables and set the timers and nutrient schedule, and if necessary aggregate that data into a centralized management frontend for multiple reservoirs.

I use my Pi to send AIS data to marinetraffic.com. It also allows you to send virtual AIS data, for those that don't have a real AIS transmitter. You won't be visible to the ships but you'll be visible to those using AIS apps.

Our station: http://www.marinetraffic.com/en/ais/details/stations/2567

What are some of the popular applications for SDR? I can't imagine it's all pirate radio and such.

Almost none of it would be pirate radio, since the most common one (RTL-SDR) is receive-only.

You can use it to tune in 2m ham radio repeaters, or listen to broadcast FM, or pick up weather radio transmissions, or track which aircraft are flying overhead, or build a little yagi antenna and hear people talking via ham radio satellite, or possibly listen to police radio depending on what your local cops use

You shouldn't need a yagi to listen to ham sats (transmit you will). A good external omnidirectional antenna should be fine.

In addition to the sats ISS always has at least one ham radio operator. They sometimes man the radio and make contacts with hams. In addition to THAT sometimes they operate SSTV (sending pictures via radio) that you would be able to pick up. Very cool stuff!

Here's a good site to see where hamsats are: http://www.amsat.org/

Nice. Now the question is how accurately you can timestamp the ADS-B replies. If you can timestamp them to within a few hundred nanoseconds, and have at least three (preferably four) receiving stations networked, you can draw a radar picture of your local airspace.

I'd like to know, but I'm not sure it is possible with a USB SDR stick. My solution in build is to use a high sample rate stereo soundcard with one channel capturing the audio from an analogue receiver and the second capturing a GPS time sync pulse.

This is how flightradar24.com and flightaware.com work

Nope, they just decode the content of the ADS-B messages.

The problem are the RTL2832U receivers. The sample rate is too low, 500ns resolution with 2MSample/s is not enough. For this reason I cannot recommend using the dvb-t sticks as ads-b receiver (the symbol rate is too high, compare nynquist theorem).

Multilateration has already be done for ADS-B on large scale, but with different receivers. There are receivers available[1] with nanosecond accuracy (and gps time synchronization).

GPS synchronization isn't needed, by choosing other flight paths to provide basic time synchronization between receivers.

[1]: <http://radarcape.com/>

There seems to be "a trick"...

http://www.rtl-sdr.com/passive-radar-dual-coherent-channel-r...

(That's on my list of "things to experiment with one day...")

This hack is awesome, thank you for the link. So many new possibilities… And cheaper than other mim̶o̶ setups.

Yep, that's been on my list for a while too! :o)

Btw, I just updated the blog post with a link to another post where I ran up a GSM network on a Pi 2 equipped with a UmTRX transceiver.

http://www.rs-online.com/designspark/electronics/eng/blog/ru...

Given that UmTRX is dual channel, has a GPS locked clock and is much higher performance is general, I'm thinking it might make for an excellent platform for experimenting with passive RADAR!

Andrew

Am I the only one who thinks this could work as an early-warning system for drone strikes?

You no longer are :).

I'm guessing (those kind of) drones don't have mode-S/ADS-B transponders.

They do have radio emissions you could triangulate.

Are you sure?

As far as I know they use satellite links. So I imagine they can avoid sending signals towards earth. I also assume they use frequency hopping in a wide range so it's harder to track.

I dunno, it's a _long_ way to a satellite, and only a short distance to the ground. Given the space/packaging constraints on a drone I wonder just how directional it's uplink antenna could possibly be. (Although I'd bet the satellite probably has a _very_ high gain antenna on board - which'd turn the tables back in their favour...)

Making a drone hard to detect is a major priority. They'll go great length to ensure it's hard to track.

However, it'd be interesting to try it. Sadly there are not many drones where I am currently.

This random webpage claims that the (probably "a") satellite uplink frequency is "13.75 - 14.5 GHz". So you would have to dig up a downconverter that works in that band. Perhaps if the drone was overhead there might be enough signal that makes it to the ground to detect. If this became popular it might turn out to be worth the bother to equip drones with receivers to detect the local oscillator leakage from such early warning systems.

As far as I know they use radar technology to spy on their targets. That was what I was referring to. I didn't read the article that thoroughly, I just picked up on "radar" signals and remembered hearing about drones having three targeting/surveillance systems....

What fun projects can I do with GNU Radio?

http://gnuradio.org/redmine/projects/gnuradio/wiki/WhatIsGR

Gotta wonder if there are already communities sharing profile information for recognizing various government agency employees/vehicles by SDR.

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