8 ms·
Turn a Raspberry Pi into an FM transmitter
- snake_plissken 13y agoHmm add a line-in, transform the signal, pipe it over to the transmitter and BOOM; silent disco!
- ColinWright 13y agoThere are two previous discussions of this that might also be worth reading: https://news.ycombinator.com/item?id=5103031 https://news.ycombinator.com/item?id=5103031 https://news.ycombinator.com/item?id=4899505 https://news.ycombinator.com/item?id=4899505
- pacofvf 13y agoyou could use this to broadcast RDS, and then tell the other cars on the road that there is a blockade ahead, it would be like that Bruce Almighty scene, well maybe not...
- antonius 13y agoIt has enough range to cover your home, DIY drive-in movie, a high school ball game, or even a bike parade (depending on the stragglers). Interesting idea... but wouldn't you need to increase the broadcast range for that to work effectively?
- ivanca 13y agoMaybe every car with the system could work as a re-transmitter?
- sbierwagen 13y agoYou can also use a bare raspi (plus a couple passives...) as a 10mW QRP transmitter: http://en.wikipedia.org/wiki/QRP_operation http://en.wikipedia.org/wiki/QRP_operation With the right software, plus favorable ionospheric conditions, you can get really, really good range. This guy did 7,600km, eastern Austria to south Florida: http://gerolfziegenhain.wordpress.com/2013/04/13/raspi-as-wspr-transmitter/ http://gerolfziegenhain.wordpress.com/2013/04/13/raspi-as-ws...
- Florin_Andrei 13y agoYou also need a very, very good antenna for that sort of stunt. QRP is tough. I'm a licensed HAM radio operator and my Tx has a 5 W final stage, so I fit right into the QRP limits. It's tough. You're at the mercy of the ionosphere all the time. 100 W amplifiers are cheap. :)
- sbierwagen 13y agoPlus he's doing QRSS using WSPR, which transmits at the breakneck pace of 1.46 baud. Supposedly WSPR works down to -28dB. http://en.wikipedia.org/wiki/WSPR_%28amateur_radio_software%29 http://en.wikipedia.org/wiki/WSPR_%28amateur_radio_software%...
- adestefan 13y agoI use a WSPR transmitter that outputs around 200mW on 20m and am easily heard all over North Americdn and Europe. I've also had two South Pacific reports. This was into a poorly tuned dipole at 35ft.
- kd0amg 13y agoYou also need a very, very good antenna for that sort of stunt. For 10mW, sure, but I've done Michigan to France on 5W with a plain old 40m loop 15-20 feet off the ground. In hindsight, I should have tried it on 3W if only to get 1000mi/W on a cloud warmer.
- post_break 13y agoDoes anyone have the ISO or a torrent of it?
- nnnnni 13y agoThere are some really good legitimate uses for this, but I'm concerned that it's going to turn into another Defense Distributed situation =-(
- Zikes 13y agoI'm not sure exactly how they compare, other than the fact that both have a potential for some form of misuse. Exactly what concerns do you have?
- a-priori 13y agoAs an amateur radio operator, I think this is fascinating, because they claim it can transmit on the 2m VHF band (144-148MHz) that's popular among hams. But I have some concerns about its signal characteristics, since you're essentially abusing digital hardware (GPIO) to produce a modulated output it wasn't designed to produce. Someone with a spectrum analyzer should check to see if it produces any nasty harmonics, or similar noise, that could interfere with other stations.
- sbierwagen 13y agoIt transmits ~10mW, though.
- fhars 13y agoIf you need a datapoint on how noisy those signals are: some people have combined a 144.6Mhz Raspberry Pi output with a narrow passive bandpass filter to generate a relatively clean and powerful 433MHz signal (the third harmonic, which is quite strong in a square wave): http://www.skagmo.com/page.php?p=projects/22_pihat http://www.skagmo.com/page.php?p=projects/22_pihat
- a-priori 13y agoYes, assuming there's strong harmonics (I'd be real surprised if there weren't), you should definitely put a bandpass filter between the Raspberry Pi and the antenna like these guys did. Thanks for the link! That's a clever way of using harmonics to your advantage.
- aortega 13y agoRecently I did a similar project in which a malicious hardware device leaks a victim's data (Password, credit card #, etc.) through a similar technique. We used an FPGA though, so with a 100 Mhz fundamental frequency we had harmonics well into the 1.5 Ghz. We called it CPU-SDR. Video here: https://sites.google.com/a/groundworkstech.com/index/blog/rsa-2014---about-cpu-backdoors-and-data-exfiltration https://sites.google.com/a/groundworkstech.com/index/blog/rs... Bonus: Using mutiple PCB traces, you have a basic Yagi-like directional antenna. Feeding different traces you can modify the RF radiation pattern it in real-time.
- simias 13y agoAfter starting the broadcast: "Keep in mind that it'll take about 15 seconds to warm up" What does that mean? What needs to warm up?
- sbierwagen 13y agoBoot up. It runs a full Linux stack, and the raspi CPU is not astonishingly fast.
- parimm 13y agoI just rebooted my rapberripi running archlinux, It took ~2 seconds from the time I rebooted it to me being able to ssh into it. The pi started to respond to ICMP packets in 19 seconds http://pastebin.com/JQmCmHXH http://pastebin.com/JQmCmHXH
- swah 13y agoHmm, maybe a Raspberry PI could be easier and more reliable replacement to virtual machines? (I love Vagrant/Virtualbox but sometimes, after putting the laptop to sleep, it stops working and I have to reboot).
- wiredfool 13y agoThey're not that fast. A single thread build of my python/c project (pillow) takes ~ 15 seconds on a vm, ~ 30 on an ancient core duo laptop, and ... still waiting on the raspberry. edit: 5:15. So 25 times slower.
- Adrock 13y agoI did an analysis of Mathematica benchmarks on the Raspberry Pi and found it to be 15x slower at best and much slower when there are CPU specific optimizations: http://adereth.github.io/blog/2014/01/06/benchmarking-mathematica-on-the-raspberry-pi/ http://adereth.github.io/blog/2014/01/06/benchmarking-mathem...
- ChuckMcM 13y agoNice! Way back I did something similar in the AM band with one of the 8 pin PIC chips [1], didn't play music though, just sent morse code. The RPi version is much nicer, you could have it talk to you :-). [1] http://www.mcmanis.com/chuck/robotics/projects/eelb.html http://www.mcmanis.com/chuck/robotics/projects/eelb.html
- gbl08ma 13y agoMake has covered it before: http://makezine.com/2012/12/10/raspberry-pi-as-an-fm-transmitter/?parent=Electronics http://makezine.com/2012/12/10/raspberry-pi-as-an-fm-transmi... Note that the news here is only the Make project on it, as this has been known and working for well over a year. The current PiFM software uses DMA from the userspace to play without clicks and without taking the whole CPU. The later versions also appear to support stereo, so I can't make much sense of this sentence in Make's tutorial (step 5): > Each file is then re-encoded into a mono format the PiFM radio can handle. If their pre-configured image is really doing this, it is doing it wrong, I think. Worth noting that the PiFM script is capable of reading from stdout, and not just play WAV files, so the possibilities go well beyond playing music off a SD card. By the way, here is the original page in a Wiki (of which Make shows a screenshot, but I found no link): http://www.icrobotics.co.uk/wiki/index.php/Turning_the_Raspberry_Pi_Into_an_FM_Transmitter http://www.icrobotics.co.uk/wiki/index.php/Turning_the_Raspb... edits: add information
- AUmrysh 13y agoWould it be possible to modify this to work at 125khz to use passive RFID?
- broabprobe 13y agoPersonal number station here we go!
- gesman 13y agoIt will transmit radio noise on many other frequencies. I played with this stuff when i was a kid to jam neighbor's TV's (they only used antennaes). Worked like a charm. It's very hard and expensive to transmit signal on a single frequency. And very easy to pollute everything.
- corin_ 13y ago> It's very hard and expensive to transmit signal on a single frequency. And very easy to pollute everything. FM transmitters for MP3 players are cheap and work well (within a very short range, but that's their use-case), see for example http://www.amazon.com/FM-Transmitters-MP3-Player-Accessories/b?ie=UTF8&node=13981621 http://www.amazon.com/FM-Transmitters-MP3-Player-Accessories... So surely it can't be that hard or expensive - unless it changes when you try to broadcast to more than a few feet away?
- sliverstorm 13y agoIf you can only broadcast two feet, who will care that you are flooding the spectrum? So I don't think you can assume they are particularly clean transmissions.
- mark-r 13y agoIf they meet FCC regulations then yes you can assume that. If they don't meet FCC regulations then they're illegal. I don't know how much policing goes on for that though.
- sliverstorm 13y agoI thought FCC regs involved a distance component? Like, they don't measure EMI right on the surface of the device.
- bqe 13y agoIf you're interested in getting into RF, I'd suggest getting a software-defined radio like bladeRF[1]. It allows you to make a lot of cool devices without being a hardware whiz. The guys who run it are extremely knowledgeable about RF and there's some really cool stuff being done with it [2][3]. [1]: http://nuand.com/ http://nuand.com/ [2]: http://bladerf.blogspot.com/ http://bladerf.blogspot.com/ [3]: http://www.irrational.net/2014/03/02/digital-atv/ http://www.irrational.net/2014/03/02/digital-atv/
- swordswinger12 13y agoI really want to learn more about this stuff! Is there a good book that introduces the basics? More technical introductions are good too.
- sbierwagen 13y agoI wish they had put the $420 price of the basic model on the front page.
- mentos 13y agoJust blew my motherboard by updating the bios via one of dell's software updates and corrupted my bios. The board doesn't have a dual bios configuration so its corrupted so I can't pull the battery or reset the CMOS. All of my research showed that most people just pony up and replace the mobo for $200. Unwilling to give up I kept researching and found that you can turn your Raspberry Pi into a flashrom to restore your bios. http://flashrom.org/RaspberryPi http://flashrom.org/RaspberryPi Waiting on female to female GPIO connectors to come in mail before I can hook my raspi up to the SPI sockets on my mobo and reflash the bios. Got my fingers crossed, if this works it will be a great win!
- simcop2387 13y agoIt should work. If you have serious trouble with that then there are also devices like the Bus Pirate[1] that can do the same thing (Though I have yet to do it myself). It's really neat how easy this kind of thing has become recently with all of the hobby electronics guys driving the market and opening up doors that 10-15 years ago looked bleak at the time (though that could just be my memory coloring it). I have used similar stuff to fix up routers (though haven't had to interface with the flashrom directly) and install openwrt.
- userbinator 13y agoWith BIOSes being serial flash these days, it's really easy to read/write them since all you need is something that can do programmed GPIO on a few lines at the right voltage. An Arduino, a parallel port on another PC, etc. A lot of PC repair shops in China will reflash BIOSes really cheaply too; they usually use a clothespin-like clip to attach to the chip so they can do it quickly without having to solder anything.
- hansjorg 13y agoReminds me of Fabrice Bellard generating TV signals (analog and digital) with a VGA card. http://bellard.org/dvbt/ http://bellard.org/dvbt/
- stephengillie 13y agoThis is awesome! Now what kind of bandwidth can we get out of this?
- soheil 13y agoWhy not just make one out of a single transistor and some resistors? #overkill
- SoulMan 13y agoGreat ! I just managed to transmit the FM signals, I used my micro USB cable stuck in 7th Pin
- guipinto 13y agoIs it possible to both receive and transmit FM simultaneously? Could this be used to create a simple, low bandwidth wireless connection between 2 pis?