Installing op25 from source on a Raspberry Pi

op25 is basically an SDR based radio scanner that can decode and manage trunked radio communication. For more information, see http://osmocom.org/projects/op25/wiki.

This procedure will install the boatbod fork. It must be installed after the gr-osmosdr step on Part 1 of these procedures.

APCO Project 25 is the digital communications standard used by many police and emergency services throughout the world. Most notably the US, Canada and Australia deploy systems based on P25. Compared to existing analog systems, P25 offers improved spectrum use, coverage and flexibility. Provision is made to ensure the confidentiality of traffic, to allow the use of trunking and the provision of data in addition to voice services.

Some services are encrypted. This software does not provide decryption.

op25 can also be set up to stream online. Online streaming is not covered here.

Install:

Prerequisites
- A recent version of cmake, newer than the version in the Raspberry Pi OS packager. Instructions are here. It is a long procedure.
  Version 3.16.3 of cmake included with Ubuntu 20.04 will work.
```
sudo apt-get install libitpp8v5 libitpp-dev libpcap0.8-dev
sudo apt-get install gnuplot-x11 # Warning: may install Qt5.11 on Raspberry Pi OS. Check the installer when it asks permission to proceed.
```

Installation

cd ~
git clone https://github.com/boatbod/op25
cd op25

sudo sed -i -- 's/^# *deb-src/deb-src/' /etc/apt/sources.list
# Tell op25 to use python3
echo "/usr/bin/python3" > op25/gr-op25_repeater/apps/op25_python

mkdir build
cd build
cmake ../
make -j 4
sudo make install
sudo ldconfig

Documentation
If you need help with your installation, you can read the help files in your install directory. Here are a few suggestions.
- Browse to directory ~/op25/op25/gr-op25_repeater/apps
  - README
  - README-configuration How to configure OP25 to monitor a P25 Trunked system
  - README-dmr DMR Support
  - README-smartnet Motorola Smartnet Support

Configuring op25 for a trunked public service scanner

op25 runs in a Terminal window and is started with a command line string.
This section is taken from Tutorial on Setting up OP25 for P25 Phase 2 Digital Voice Decoding.
I have worked out some of the details for the SDRplay RSP1A.
The tutorial is detailed below:

OP25 For Dummies – Or how to build a police scanner for $30 (Part 1)
OP25 Raspberry Pi Streaming Part 2
OP25 on a Raspberry Pi (part 3)
To get started, we need to find the control frequency and NAC for the service in your area.
- Go to https://www.radioreference.com/apps/db/
- Scroll to the section entitled Search Trunked Radio Information.
- You should be able to find your police, Fire, Utilities, etc. by the state unless you know the other details. I chose the State of Michigan.
- Click on a service in your area.
- In the list provided, find a service that you wish to monitor. Look for the control channel frequency in red with a c appended to it. You can tune to it with a program like GQRX. It will be a constant signal and will sound like noise. Close your SDR program.
- Open a Terminal window.
```
cd ~/op25/op25/gr-op25_repeater/apps
```
- Paste a command similar to this into the Terminal. Change -f frequency to your control channel. -q is the frequency correction for your SDR.
```
# For SDRplay:
./rx.py --args 'driver=sdrplay,soapy=0' -N 'IFGR:28,RFGR:2' -S 2500000 -x 1 -f 855.2875e6 -o 1e3 -q -1

# For HackRF
./rx.py --args 'hackrf' -g 65 -N 'RF:14,IF:32,BB:26' -S 1000000 -x 1 -f 855.2875e6 -o 50e3 -q -1
```
- The terminal will display the control channel frequency and the tuning offset in parenthesis like this: Frequency 855.287500(0)
  If you get a lot of errors similar to p25_framer::rx_sym() tuning error +1200, you may need to make a frequency correction.
  Pressing "," lowers the fine tuning frequency by 100 Hz. Pressing "." increases the fine tuning frequency by 100 Hz. Slowly change fine tuning (in parenthesis) until the errors stop and decoding begins.
  Take the frequency from the parenthesis and add it to the end of the command line with a "-d" like this: -d 600. Press "q" to stop op25. Enter the command into the terminal again with the correction like this:
```
# For SDRplay:
./rx.py --args 'driver=sdrplay,soapy=0' -N 'IFGR:28,RFGR:2' -S 2500000 -x 1 -f 855.2875e6 -o 1e3 -q -1 -d 600

# For HackRF:
./rx.py --args 'hackrf' -g 65 -N 'RF:14,IF:32,BB:26' -S 1000000 -x 1 -f 855.2875e6 -o 50e3 -q -1 -d 600
```
- The display should be free of errors. The top line should look similar to this:
```
NAC 0x799 WACN 0x92493 SYSID 0x796 855.287500/810.287500 tsbks 10
```
- Take a note of the NAC number, which in this case is 0x799.

Make the configuration files

While still in the apps directory, open the tab delimited trunk.tsv. If you have a spreadsheet program, use that. You may use a text editor of you are careful. In a spreadsheet, it should look similar to this:

Sysname	Control Channel List	Offset	NAC	Modulation	TGID Tags File	Whitelist	Blacklist	Center Frequency
Washtenaw County	855.28750	0	0x799	cqpsk	washtenaw.tsv

Enter the NAC that you found. Using radioreference.com, enter the data in the fields the best that you can. TGID Tags File will be your database of local talkgroups. Save the file in the ~/op25/op25/gr-op25_repeater/apps directory, keeping the tab delimited format.

Create a new tab delimited spreadsheet for the TGID Tags File. Using radioreference.com, enter data from the DEC (Talkgroup ID) column in column 1, Description (Tag) in column 2, and optionally, a priority in column 3. LOWER numbers have HIGHER priority. Default is 3 for anything with no tag specified.

2191 Washtenaw County Ann Arbor Dispatch [Alternate] 1

2237 Huron Valley Ambulance: Dispatch 3

If you click "List All in one table", you can copy and paste the entire table into the spreadsheet. Delete the unnecessary columns, sort if you prefer. Add priorities if you want them. Save in the ~/op25/op25/gr-op25_repeater/apps directory as the file name that you entered into trunk.tsv column "TGID Tags File", keeping the tab delimited format.
The optional blacklist file
You may want to blacklist the secure (encrypted) talkgroups as you will not be able to hear their audio with this program.
The blacklist excludes numerically listed TGIDs but allows everything else to play. Ranges of whitelists and blacklists are specified by settings the starting tgid followed by a tab character and the ending tgid.
- Create the initial file:
```
cd ~/op25/op25/gr-op25_repeater/apps
grep "\- Secure" michigan.tsv > blacklist.tsv
```
- This will create a file with all lines that have "- Secure" in them. Edit this file in a spreadsheet and delete all columns except the first column with DEC (Talkgroup ID). If you make ranges, the spreadsheet will save the file with a tab to start the second column. You must delete these extra tabs, as those talkgroups will not be blacklisted.
- Add blacklist.tsv to trunk file (trunk.tsv) in the Blacklist column.
The whiltelist file works similarly, except that it limits monitored TGIDs to just those listed numerically in the file.

Run the program

Open a Terminal window, paste and execute these commands, customized for your setup.

# For SDRplay:
cd ~/op25/op25/gr-op25_repeater/apps
./rx.py --args 'driver=sdrplay,soapy=0' -N 'IFGR:28,RFGR:1' -S 2500000 -x 1 -f 855.2875e6 -o 1e3 -q -1 -d 600 -T michigantrunk.tsv -V -2 -O pulse -U 2> stderr-stream0.2

# For HackRF:
cd ~/op25/op25/gr-op25_repeater/apps
./rx.py --args 'hackrf' -g 65 -N 'RF:14,IF:32,BB:26' -S 1000000 -x 1 -f 855.2875e6 -o 50e3 -q -1 -d 1200 -T michigantrunk.tsv -V -2 -U 2> stderr-stream0.2

Add -O pulse to the command line if your audio is garbled. You may have to experiment to get all of the SDR apps to work.
I specified -x 1 to set the audio gain. Default = 1.0. Specifying -x 0.8 may be better as some signals are extremely loud.

The command line syntax can be displayed by typing ./rx.py -h.

This should get you up and running. You can read the tutorials mentioned above for more details. You probably will have to adjust FINE_TUNE and the gains for your SDR, antenna, etc.
If you find that there is a wide range in audio levels between the various signals, I recommend using liquidsoap
There is a sample liquidsoap configuration file in the ~/op25/op25/gr-op25_repeater/apps directory named op25.liq. You probably need to change some of the parameters. The *.liq file needs to have execute permission.
```
sudo apt-get install liquidsoap
```
- Liquidsoap 1.4.1 and later needs some modifications if you get "Error 4: Undefined variable mksafe."
  - Find your liquidsoap version
```
apt list -a liquidsoap
Listing... Done
liquidsoap/testing,now 1.4.1-2 arm64 [installed]
```
  - Replace the 1.4.1 in the commands below with your actual version and execute these commands in a terminal.
```
sudo mkdir /usr/share/liquidsoap/1.4.1
sudo ln -s /usr/share/liquidsoap/libs /usr/share/liquidsoap/1.4.1/
```
- If you get the error: no argument labeled "rms_window"!, edit your configuration file i.e. op25.liq and change "rms_window" to "window". The line number that needs to be changed will be in the error message.
- Instead of starting rx.py as specified above, open 3 Terminal windows:
  - Terminal #1:
```
# For SDRplay:
cd ~/op25/op25/gr-op25_repeater/apps
./rx.py --args 'driver=sdrplay,soapy=0' -N 'IFGR:28,RFGR:1' -S 1000000 -x 1 -f 855.2875e6 -o 1e3 -q -1 -d 700 -T michigantrunk.tsv -V -2 -w 2> stderr-stream0.2

# For HackRF:
cd ~/op25/op25/gr-op25_repeater/apps
./rx.py --args 'hackrf' -g 65 -N 'RF:14,IF:32,BB:26' -S 1000000 -x 1 -f 855.2875e6 -o 50e3 -q -1 -d 1200 -T michigantrunk.tsv -V -2 -w 2> stderr-stream0.2
```
  - Terminal #2:
```
cd ~/op25/op25/gr-op25_repeater/apps
./op25.liq
```
  - Terminal #3: (optional log window)
```
cd ~/op25/op25/gr-op25_repeater/apps
tail -f stderr-stream0.2
```

HTTP Console
The OP25 GUI dashboard in a web browser. Basically, we add -l 'http:0.0.0.0:8080' to the command and remove the error redirect, so errors will appear in the terminal.

Open 2 Terminal windows:

Terminal #1:

# For SDRplay:
cd ~/op25/op25/gr-op25_repeater/apps
./rx.py --args 'driver=sdrplay,soapy=0' -N 'IFGR:28,RFGR:1' -S 1000000 -x 1 -f 855.2875e6 -o 1e3 -q -1 -d 700 -T michigantrunk.tsv -V -2 -v 1 -w -l 'http:0.0.0.0:8080'

# For HackRF:
cd ~/op25/op25/gr-op25_repeater/apps
./rx.py --args 'hackrf' -g 65 -N 'RF:14,IF:32,BB:26' -S 1000000 -x 1 -f 855.2875e6 -o 50e3 -q -1 -d 1200 -T michigantrunk.tsv -V -2 -v 1 -w -l 'http:0.0.0.0:8080'

Terminal #2:

cd ~/op25/op25/gr-op25_repeater/apps
./op25.liq

Open a web browser and enter the URL: http://127.0.0.1:8080/. You can also use the IP address of your Raspberry Pi.
To stream the audio over the Internet, you probably will have to use Icecast.

Configuring op25 to receive two channel DMR
- You will need a configuration file. An example that uses op25 built-in audio for SDRplay is here. and for HackRF is here. Right-click on the link and save as... save it in ~/op25/op25/gr-op25_repeater/apps
  The IFGR gain setting has no effect unless you add the line "gain_mode": false, in the "devices" section. This seems to be a hardware AGC setting, so that won't work unless "gain_mode" is omitted or "gain_mode": true, is present.
- The receive frequency, audio_gain, plot etc. are in the file. If you use the fft plot, it may take enough CPU time to cause buffer overruns as evidenced by a series of "O"s in the message window.
  If you have stereo audio, the two DMR channels will be played in separate speakers, so may only hear sound from one speaker.
  - Open a Terminal window:
    - This command will display only messages that contain the talkgroup: (be sure to specify the .json file for your SDR)
```
# For SDRplay:
cd ~/op25/op25/gr-op25_repeater/apps
./multi_rx.py -c dmr_cfg.json -v 10 3>&1 1>&2 2>&3 | grep DSTADDR

# For HackRF:
cd ~/op25/op25/gr-op25_repeater/apps
./multi_rx.py -c dmr_cfg_hackrf.json -v 10 3>&1 1>&2 2>&3 | grep DSTADDR
```
      DSTADDR() is the talkgroup in hexadecimal, SRCADDR() is the address of the radio that is transmitting in hexadecimal.You need to convert these numbers to decimal before you look them up.
- If you find that there is a wide range in audio levels between the various signals, I recommend using liquidsoap
  Download the DMR external audio configuration file for RSP1A here, HackRF here. Right-click on the link and save as... save it in ~/op25/op25/gr-op25_repeater/apps
  The RSP1A IFGR gain setting has no effect unless you add the line "gain_mode": false, in the "devices" section. This seems to be a hardware AGC setting, so that won't work unless "gain_mode" is omitted or "gain_mode": true, is present.
- Copy your liquidsoap configuration file in the ~/op25/op25/gr-op25_repeater/apps directory named op25.liq to op25-2_channel.liq.
  In op25-2_channel.liq, find "./audio.py -x 1.5 -s" in the file and change it to "./audio.py -2 -x 1.0 -s" so that you can receive 2 channels. (The -x 1.5 may already have changed) Make it executable.
- Instead of starting multi_rx.py as specified above, open 2 Terminal windows:
  These commands will display all of the error messages in the terminal window.
  - Terminal #1:
```
# For SDRplay:
cd ~/op25/op25/gr-op25_repeater/apps
./multi_rx.py -c dmr_cfg_ext_audio.json -v 10

# For HackRF:
cd ~/op25/op25/gr-op25_repeater/apps
./multi_rx.py -c dmr_cfg_hackrf_ext_audio.json -v 10
```
  - Terminal #2:
```
cd ~/op25/op25/gr-op25_repeater/apps
./op25-2_channel.liq
```
- HTTP Console does not seem to be implemented for DMR.
Motorola Type II Smartnet
- Find the Smartnet service that you want to monitor here: https://www.radioreference.com/apps/db/
  Normally, this function requires two SDRs, but SDR hardware with a high sample rate can be shared between channels, but only if tuning is disabled (tunable=false)
  You will have to configure the sample rate to be high enough to cover the entire frequency range of the service you will be monitoring. High sample rates also bring high CPU usage and may result in buffer overruns from GNU Radio as evidenced by a series of "O" characters in the message terminal. Press a number key that would bring up a graph twice such as 3 to restart monitoring.
- Browse to directory ~/op25/op25/gr-op25_repeater/apps
- Edit a config file. Here is an example using one RSP1A: smartnet_test.json or for HackRF: smartnet_hackrf.json. There is also an example in your install directory: smartnet_example.json
  Here are some of the important items that need to be configured.
  - Ensure that the "device" entries in the "channels" section match the device "name" in the "devices" section.
  - "args", "gains", "gain_mode"
  - "frequency", use a frequency in the center of the range used by the service you want to monitor.
  - "name" to match "device" entries in the "channels" section
  - "offset": 50e3 This is to avoid the DC offset in most SDRs. Without it, HackRF has a big spike right on the receive frequency.
  - "tunable": false if you only have one device
  - "control_channel_list" in the "trunking" section, comma separated list of the control channels found on radioreference.com
- Run the program
  - Open 2 Terminal windows:
    - Terminal #1: (be sure to specify the .json file for your SDR)
```
# For SDRplay:
cd ~/op25/op25/gr-op25_repeater/apps
./multi_rx.py -v 4 -c smartnet_test.json 2> stderr.2

# For HackRF:
cd ~/op25/op25/gr-op25_repeater/apps
./multi_rx.py -v 4 -c smartnet_hackrf.json 2> stderr.2
```
    - Terminal #2:
```
cd ~/op25/op25/gr-op25_repeater/apps
tail -f stderr.2
```
  - Use the right and left arrow keys to cycle through the pages. The second page will show the active talkgroup with the tags from your "tgid_tags_file" file specified in your configuration file.
- HTTP Console
  The Smartnet GUI dashboard in a web browser. Basically, in the .json setting file "terminal" section we uncomment (remove the "#") from "terminal_type": "http:127.0.0.1:8080" and put a "#" at the start of "#terminal_type": "curses". "terminal_type". "http:0.0.0.0:8080" will allow access from any IP address on your network.
  In the "audio" section, remove the contents of "instance_name": "", leaving just the quotes as shown. This will disable the internal audio player and allow you to use an external audio player such as liquidsoap.
  An example .json file for SDRplay is here. and for HackRF is here. Right-click on the link and save as... save it in ~/op25/op25/gr-op25_repeater/apps.
  Removing the error redirect will cause the errors to appear in the terminal.
  - Open 2 Terminal windows:
    - Terminal #1: (be sure to specify the .json file for your SDR)
```
# For SDRplay:
cd ~/op25/op25/gr-op25_repeater/apps
./multi_rx.py -v 4 -c smartnet_test_http.json

# For HackRF:
cd ~/op25/op25/gr-op25_repeater/apps
./multi_rx.py -v 4 -c smartnet_hackrf_http.json
```
    - Terminal #2:
```
cd ~/op25/op25/gr-op25_repeater/apps
./op25.liq
```
  - Open a web browser and enter the URL: http://127.0.0.1:8080/. You can also use the IP address of your Raspberry Pi if you used "http:0.0.0.0:8080" in your .json file.
    To stream the audio over the Internet, you probably will have to use Icecast.

Back to the index

2191	Washtenaw County Ann Arbor Dispatch [Alternate]	1
2237	Huron Valley Ambulance: Dispatch	3