mirror of https://github.com/drowe67/pirip.git
129 lines
5.3 KiB
Markdown
129 lines
5.3 KiB
Markdown
# Pi Radio IP
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Minimal hardware IP over VHF/UHF Radio using RpiTx and RTLSDRs [1].
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# Project Plan and Status
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Currently working on M4 -Over The Air (OTA) tests.
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| Milestone | Description |
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| --- | --- |
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| M1 | ~~Proof of Concept Physical Layer~~ |
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| M2 | ~~Git repo for project, integrated tx and rx applications~~ |
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| M3 | ~~Simple GUI Dashboard that can be used to tune and debug link~~ |
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| M4 | first OTA tests using uncoded modem |
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| M5 | Pi running Tx and Rx |
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| M6 | Add LDPC FEC to waveform |
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| M7 | Bidirectional half duplex Tx/Rx on single Pi |
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| M8 | TAP/TUN integration and demo IP link |
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| M9 | Document how to build simple wire antennas |
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# Building
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This procedure builds everything locally, so won't interfere with any installed versions of the same software.
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## RpiTx Transmitter
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ssh into your Pi, then:
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```
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$ git clone https://github.com/drowe67/pirip.git
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$ cd pirip
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$ ./build_codec2.sh
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$ ./build_rpitx.sh
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$ cd tx && make
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```
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## RTLSDR FSK Receiver
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On your laptop/PC:
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```
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$ sudo apt update
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$ sudo apt install libusb-1.0-0-dev git cmake
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$ ./build_codec2.sh
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$ ./build_csdr.sh
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$ ./build_rtlsdr.sh
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```
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# Testing
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1. Transmit two tone test signal for Pi:
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```
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pi@raspberrypi:~/pirip/tx $ sudo ./fsk_rpitx -t /dev/null
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```
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1. Transmit test frames from Pi for 60 seconds:
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```
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pi@raspberrypi:~/pirip/tx $ ../codec2/build_linux/src/fsk_get_test_bits - 600000 | sudo ./fsk_rpitx -
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```
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1. Receive test frames on x86 laptop for 5 seconds (vanilla rtl_sdr):
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```
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~/pirip$ Fs=240000; rtl-sdr-blog/build_rtlsdr/src/rtl_sdr -g 49 -s $Fs -f 144490000 - | codec2/build_linux/src/fsk_demod --fsk_lower 500 --fsk_upper 25000 -d -p 24 2 240000 10000 - - | codec2/build_linux/src/fsk_put_test_bits -
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1. Receive test frames on x86 laptop for 5 seconds (vanilla rtl_sdr at Fs=1.8MHz):
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```
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Fs=1800000; ./src/rtl_sdr -g 49 -s $Fs -f 144500000 - | csdr convert_u8_f | csdr fir_decimate_cc 45 | csdr convert_f_s16 | ../../codec2/build_linux/src/fsk_demod --fsk_lower 500 -c 2 40000 1000 - - | ../../codec2/build_linux/src/fsk_put_test_bits -
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```
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1. Receive test frames on x86 laptop for 5 seconds (integrated rtl_fsk):
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```
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~/pirip$ Fs=240000; tsecs=5; ./rtl-sdr-blog/build_rtlsdr/src/rtl_fsk -g 49 -f 144490000 - -n $(($Fs*$tsecs)) | codec2/build_linux/src/fsk_put_test_bits -
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```
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Note this is tuned about 10kHz low, to put the two tones above the rtl_sdr DC line.
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1. Demod GUI Dashboard. Open a new console and start `demod_gui.py`:
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```
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~/pirip$ netcat -luk 8001 | ./src/dash.py
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```
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In another console start the FSK demod:
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```
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~/pirip$ Fs=240000; tsecs=20; ./rtl-sdr-blog/build_rtlsdr/src/rtl_fsk -g 1 -f 144490000 - -n $(($Fs*$tsecs)) -u localhost | codec2/build_linux/src/fsk_put_test_bits -
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```
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1. Automated loopback tests. Connect your Pi to your RTLSDR via a 60dB attenuator
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Using vanilla `rtl_sdr`:
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```
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./test/loopback_rtl_sdr.sh
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```
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Using integrated `rtl_fsk`:
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```
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./test/loopback_rtl_fsk.sh
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```
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You can monitor `loopback_rtl_fsk.sh` using `dash.py` as above.
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1. Using a HackRF as a transmitter, useful for bench testing the link. The relatively low levels out of the HackRF make MDS testing easier compared to attenuating the somewhat stronger signal from the Pi.
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This example generates 1000 bit/s FSK with a 2000Hz shift:
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```
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cd codec2/build_linux/src
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./fsk_get_test_bits - 60000 | ./fsk_mod -c -a 32767 2 40000 1000 1000 2000 - - | ../misc/tlininterp - t.iq8 100 -d -f
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```
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The output samples are at a sample rate of 4MHz, and a frequency offset of +1 MHz. They can be played out of the HackRF with:
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```
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hackrf_transfer -t t.iq8 -s 4E6 -f 143.5E6
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```
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The signal will be centred on 144.5 MHz (143.5 + 1 MHz offset).
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1. Noise Figure Testing
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Connect a signal generator to the input of the RTLSDR. Set the frequency to 144.5MHz, and amplitude to -100dBm.
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The following command pipes the RTL output to an Octave script to measure noise figure. You need the CSDR tools and Octave installed:
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```
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$ cd ~/pirip/rtl-sdr-blog/build_rtlsdr/src
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$ ./rtl_sdr -g 50 -s 2400000 -f 144.498E6 - | csdr convert_u8_f | csdr fir_decimate_cc 50 | csdr convert_f_s16 | octave --no-gui -qf ~/pirip/codec2/octave/nf_from_stdio.m 48000 complex
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```
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A few Octave plot windows will pop up. Adjust your signal generator frequency so the sine wave is between 2000 and 4000, the
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script will print the Noise Figure (NF). Around 6-6.2 dB was obtained using RTL-SDR.COM V3s using"-g 50"
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See also codec2/octave/nf_from_stdio.m and [Measuring SDR Noise Figure in Real Time](http://www.rowetel.com/?page_id=6172).
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# Reading Further
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1. [Open IP over VHF/UHF](http://www.rowetel.com/?p=7207) - Blog post introducing this project
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1. [Open IP over VHF/UHF 2](http://www.rowetel.com/?p=7334) - Second blog post on uncoded OTA tests
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1. [Previous Codec 2 PR discussing this project](https://github.com/drowe67/codec2/pull/125)
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1. [Codec 2 FSK Modem](https://github.com/drowe67/codec2/blob/master/README_fsk.md)
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1. [RpiTx](https://github.com/F5OEO/rpitx) - Radio transmitter software for Raspberry Pis
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1. [rtlsdr driver](https://github.com/librtlsdr/librtlsdr) - Our rtlsdr driver is forked from this fine repo.
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1. [Measuring SDR Noise Figure in Real Time](http://www.rowetel.com/?page_id=6172) |