phone

This is a repository containing some code artifacts but mostly testing fragments for a project to develop a device to connect landline phones to other landline phones via a private VoIP network. At time of writing of this README (July 2024) efforts are mostly focused on the design of the hardware side of the project, but this repository may come to house more complete companion software as the project grows.

1. Ring phone via software
   • Completed in ring.py
2. Play audio on phone speaker
   • Completed in wav.py
3. Receive audio from phone and convert to digital signal
4. Parse DTMF signals for dialing
5. Create system for initial phone setup
6. Create web app for call routing and social networking

Development Utilities

SSH

The Pi is set up with the hostname peterpi.local and can be SSH'ed to using the username recurse.

ssh recurse@peterpi.local

SSH setup

sudo sed --in-place=.bak --expression='s/^#PermitEmptyPasswords no/PermitEmptyPasswords yes/g' /etc/ssh/sshd_config
sudo systemctl restart sshd
sudo passwd -d recurse

Dial tone generator

These commands are used to send sine wave signals to the speakers of the Pi. By correctly routing the output audio device of the Pi to "headphones" routed to pins, these signals can be sent to the phone. The following two sine waves are the frequencies used in a standard dial tone.

speaker-test -t sine -f 350 -l0
speaker-test -t sine -f 440 -l0

Cross-compile to Rasppi (old stinky cross-rs way)

cross build --target=arm-unknown-linux-gnueabihf

Device Tree compile

scp phoneodeo.dts recurse@peterpi.local:
scp bootconfig.txt recurse@peterpi.local:

dtc -@ -H epapr -O dtb -o phoneodeo.dtbo -Wno-unit_address_vs_reg phoneodeo.dts
sudo cp phoneodeo.dtbo /boot/overlays
sudo chown root:root bootconfig.txt
sudo chmod 755 bootconfig.txt
sudo cp bootconfig.txt /boot/firmware/config.txt

Install phreak.service

scp goertzel/phreak.service recurse@peterpi.local:
scp goertzel/target/arm-unknown-linux-gnueabihf/release/goertzel recurse@peterpi.local:

sudo chown root:root ~/phreak.service
sudo chmod 777 ~/phreak.service
sudo mv ~/phreak.service /etc/systemd/system
sudo systemctl disable phreak.service
sudo systemctl enable phreak.service

Install .asoundrc

scp asoundrc recurse@peterpi.local:.asoundrc

sudo cp .asoundrc /root

Set volume

amixer sset PCM -M '40%'
sudo alsactl store

Take down Wi-Fi

sudo nmcli connection delete 'Recurse Center'; sudo reboot

Install cross-compiler

brew tap messense/macos-cross-toolchains
brew install arm-unknown-linux-gnueabihf

cargo build --release --target=arm-unknown-linux-gnueabihf

PBX

wget https://downloads.asterisk.org/pub/telephony/asterisk/asterisk-20-current.tar.gz
tar -xzvf asterisk-20-current.tar.gz
cd asterisk-20.9.3
./contrib/scripts/install_prereq install &&
./configure &&
make &&
make install

socat wiring on Windows

Cygwin:

socat -t30 -T30 UDP4-RECVFROM:5060,fork UDP4:"$(wsl hostname -I | tr -d ' ')":5062 &
socat -t30 -T30 UDP4-RECVFROM:5061,fork UDP4:"$(wsl hostname -I | tr -d ' ')":5063 &

ssh wiring on Windows:

PowerShell (administrator):

netsh interface portproxy add v4tov4 listenaddress=x.x.x.x listenport=22 connectaddress=$($(wsl hostname -I).Trim()) connectport=22
netsh advfirewall firewall add rule name=”Open Port 22 for WSL2” dir=in action=allow protocol=TCP localport=22

Relevant Material

• SLIC datasheet
• gpiozero docs
• Cringely-named DT overlay
  • Comment out playback and codec_out
  • dai-tdm-slot-width to 24
  • Add in capture_link block mclk-fs = <256>
  • Add in r_codec_dai system-clock-frequency = <2560000>