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As a noob to radio stuff, I had to do a lot of trial and error to figure out the exact format that pifm was expecting. The exact command I had to use was: ffmpeg -i sample.mp3 -acodec pcm_s16le -ar 48000 -ac 1 sample.wav
94 lines
4.0 KiB
Markdown
94 lines
4.0 KiB
Markdown
**rpitx** is a radio transmitter for Raspberry Pi (B,B+ and PI2) which output directly to GPIO.
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*(Created by Evariste Courjaud F5OEO. Code is GPL)*
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*
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<h1> Installation </h1>
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git clone the repository
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cd rpitx
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make sure to have access to Internet to download packages : libsndfile1-dev and imagemagick otherwise install them manualy
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./install.sh
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<h1>Hardware</h1>
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Plug a wire on GPIO 18, means Pin 12 of the GPIO header ([header P1](http://elinux.org/RPi_Low-level_peripherals#General_Purpose_Input.2FOutput_.28GPIO.29)): this act as the antenna. Length depend on transmit frequency, but with few centimeters it works for local testing.
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<h1>Short manual</h1>
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<h2> General </h2>
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**rpitx** is the main software to transmit. It allows to transmit
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- from **IQ** files *.iq (could be generated by external software like gnuradio or by some few examples of modulations).
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- from **Frequency/Time** files *.ft (generally used implement easily digital modes)
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Usage:
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rpitx [-i File Input][-m ModeInput] [-f frequency output] [-s Samplerate] [-l] [-p ppm] [-h]
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-m {IQ(FileInput is a Stereo Wav contains I on left Channel, Q on right channel)}
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{IQFLOAT(FileInput is a Raw float interlaced I,Q)}
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{RF(FileInput is a (double)Frequency,Time in nanoseconds}
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{RFA(FileInput is a (double)Frequency,(int)Time in nanoseconds,(float)Amplitude}
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{VFO (constant frequency)}
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-i path to File Input
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-f float frequency to output on GPIO_18 pin 12 in khz : (130 kHz to 750 MHz),
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-l loop mode for file input
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-p float frequency correction in parts per million (ppm), positive or negative, for calibration, default 0.
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-d int DMABurstSize (default 1000) but for very short message, could be decrease
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-h help (this help).
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<h2> Modulation samples </h2>
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Some modulations are included in the software and can be easily extended. They create files which could be ingest by rpitx.
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Some output in IQ (like ssb) other in FT(like sstv)
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<h3> SSB modulation </h3>
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**pissb** convert an audio file (Wav 48KHZ mono only!) to SSB (USB right now) and output it on a IQ file.
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Assuming your audio file is in the folder
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```
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./pissb audio48mono.wav ssbIQ.wav
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```
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You could then transmit it on 50MHZ (please set a correct frequency to be legal)
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```
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sudo ./rpitx -m IQ -i ssbIQ.wav -f 50000 -l
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```
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A sample script : **testssb.sh** is included.
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<h3> FM modulation </h3>
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**pifm** convert an audio file (Wav, 48KHz, 1 channel, pcm_s16le codec) to Narrow band FM (12.5khz excursion) and output it on a .ft file.
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Assuming your audio file is in the folder
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```
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./pifm audio48mono.wav fm.ft
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```
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You could then transmit it on 100MHZ (please set a correct frequency to be legal)
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```
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sudo ./rpitx -m RF -i fm.ft -f 100000 -l
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```
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A sample script : **testfm.sh** is included.
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<h3> SSTV </h3>
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**pisstv** convert a picture(rgb) to a SSTV .ft file
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if you have a jpeg picture 320*256 you could transform it to rgb with imagemagick
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convert -depth 8 picture.jpg picture.rgb
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Then convert to .ft file :
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```
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./pisstv picture.rgb picture.ft
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```
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And then transmit it to 100MHZ (please set a correct frequency to be legal)
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```
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sudo ./rpitx -m RF -i picture.ft -f 100000
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```
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A sample script : **snapsstv.sh** allows to grab a picture from the Picamera and transmit it
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<h3> FSQ </h3>
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**pifsq** allows to send a text with the new FSQ modulation
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It is still in test.
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A sample script : **testfsq.sh** allows to send a text with FSQ
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<h3> VFO </h3>
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A **VFO** mode is provided to allows precise frequency resolution.
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Example for generate a carrier on 100MHZ(please set a correct frequency to be legal)
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```
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sudo ./rpitx -m VFO -f 100000
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```
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<h1> Notes </h1>
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All rights of the original authors reserved.
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Special thanks to Sylvain Azarian F4GKR for improving SSB modulation
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Inspired by
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* http://pe1nnz.nl.eu.org/2013/05/direct-ssb-generation-on-pll.html
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* http://www.icrobotics.co.uk/wiki/index.php/Turning_the_Raspberry_Pi_Into_an_FM_Transmitter
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* https://github.com/richardghirst/PiBits/pull/18
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* http://www.bellard.org/dvbt/
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