README.md for analog microphone variant

ESP32 door bell to sip call

On startup the application associates with the compiled in wlan access point and registers on the SIP server.

Once a signal is detected on the selected GPIO, a call is initiated to a target number. On the phone, the custom string is displayed. After the configured timeout is elapsed, the call is canceled. If the signal is detected again, before the timer is elapsed, the timer is started again.

Tested with:

• AVM Fritzbox 7390
• AVM Fritzbox 7490 (Firmware 7.28)
• AVM Fritzbox 7590
• local FreeSWITCH installation

Programming

The source code is mixed C and C++.

This application is to be used with Espressif IoT Development Framework_ (ESP-IDF). It is tested with version v4.3.1 (rev 2e74914051d14ec2290fc751a8486fb51d73a31e)

Please check ESP-IDF docs for getting started instructions.

Building ++++++++

The project now uses cmake, so after initializing your environment with the relevant variables from esp-idf you can use idf.py to build, flash etc::

cd <this project's root dir> idf.py menuconfig idf.py build idf.py flash monitor

To build for another ESP32 soc, e.g. the ESP32C3::

cd <this project's root dir> idf.py set-target esp32c3 idf.py menuconfig idf.py build idf.py flash monitor

See Selecting soc build target_ for more details.

To build this project for the pc (linux, e.g. ubuntu or fedora), a sample (not all features are supported, yet)::

mkdir cd cmake <this project's root dir>/native make

The sip server configuration must be done in the defines of the file <this project's root dir>/native/main.cpp.

The following libraries are required for this (e.g. on fedora)::

sudo dnf install asio-devel mbedtls-devel

Code formatting +++++++++++++++

Clang-format is used to format the code. The settings are stored in .clangformat. The format of external files, e.g. components/sip_client/include/boost/sml.hpp should not be changed. To run clang-format (e.g. version 12) over all files::

find . -regex '.*.cpp\|cc\|cxx\|h' -exec clang-format -style=file -i {} ;

Hardware

An ESP32 board can be used. Only one external GPIO (input is sufficient) must be available, to detect the call trigger. To test this, two PC817 opto coupler are used to detect the AC signal (about 12V from the bell transformer). The input diodes of the opto couplers are connected in parallel and opposing directions. In series, a 2k Resistor is used. This may have to be tweaked according to the input voltage. The output transistors of the opto couplers are connected in parallel in the same polarity to pull the signal to ground, if a current flows through one of the input diodes. A pull up resistor (either internal in the ESP32 or external) must be used to pull the signal to 3V3 if no input current is detected and the output transistors are switched off.

Instead of two PC817 opto couplers, one PC814 can be used to detect the AC signal. Because of the different CTR, the resistor values must be tweaked. If it is sufficient to only detect one half-wave of the AC signal (this is normally the case) one PC817 opto coupler and a simple diode (e.g. 1N4148) is sufficient. The diode ensures that the voltage of the input diode of the opto coupler is not above the threshold. The 1N4148 must be connected anti-parallel to the input diode of the PC817.

.. image:: hw/door_bell_input_schematic.svg :width: 600pt

If the bell transformer delivers enough power, the ESP32 can be powered from it. A bridge rectifier, a big capacitor and a cheap switching regulator board can be used for that.

License

If not otherwise specified, code in this repository is Copyright (C) 2017-2021 Christian Taedcke hacking@taedcke.com, licensed under the Apache License 2.0 as described in the file LICENSE.

Misc Information

On the AVM Fritzbox the number **9 can be used to let all connected phones ring.

.. _Espressif IoT Development Framework: https://esp-idf.readthedocs.io/ .. _Selecting soc build target: https://docs.espressif.com/projects/esp-idf/en/v4.3.1/esp32c3/api-guides/build-system.html#selecting-the-target

README.md from MEMS project variant

ESP32 simple VoIP phone

.. image:: img/dev.png :width: 600pt

On startup the application associates with the compiled in wlan access point and registers on the SIP server.

Once a signal is detected on the selected GPIO, a call is initiated to a target number. On the phone, the custom string is displayed.

Adafruit components operating on the i2s bus have been selected for audio support.

The project aims to show the resources of the small and cheap ESP32 module and is based on the chrta's project.

Programming

The source code is mixed C and C++.

This application is to be used with Espressif IoT Development Framework_ (ESP-IDF).

Please check ESP-IDF docs for getting started instructions.

Hardware

An ESP32 board can be used. Only one external GPIO (input is sufficient) must be available, to detect the call trigger.

The software has been adapted for use on the WEMOS LOLIN32 development board with an integrated 0.96" monochrome OLED SSD1306 display, informing about the state of the device.

.. image:: img/main.png :width: 600pt

The audio output is dealt with by the DAC stereo decoder on the I2S bus, model UDA1334A from Adafruit, while the sound sampling system is the MEMS I2S microphone model SPH0645LM4H, also manufactured by Adafruit.

In order to verify the built-in VoIP client, the Asterisk VoIP server was launched in the test environment and the voice connection was successfully completed. RAM usage fluctuated around 319 kB from ESP32 512 kB available in ESP32.

.. image:: img/testcall.png :width: 600pt

The maximum jiiter in the stream from the built-in device was 5.1 ms, while the average was 4.14 ms - achieved value jitter is acceptable for a typical VoIP client.

License

If not otherwise specified, code in this repository is Copyright (C) 2017 Christian Taedcke hacking@taedcke.com, licensed under the Apache License 2.0 as described in the file LICENSE.