Android Codec2 Walkie-Talkie

Minimalistic Android KISS Bluetooth/USB modem client for Amateur Radio DV (digital voice) communication by using open source Codec2.

Introduction

This minimalistic Android application is a digital voice frontend for your radio. It connects to your radio KISS Bluetooth/USB modem, sends and receives Codec2 audio frames, which are encapsulated inside KISS frames. It does not deal with radio management, modulation, etc, it is up to your modem and radio, it could be just AFSK1200, GMSK 9600, LoRa, FSK, FreeDV or any other modulation scheme. Radio just needs to expose KISS Bluetooth interface for speech frames.

Requirements

• Android 6.0 (API 23) or higher
• Modem or transceiver which supports KISS protocol over Bluetooth or USB

Features

• PTT button, push and talk, Codec2 speech frames will be transmitted to the modem
• USB serial connectivity (115200 bps, 8 data bits, 1 stop bit, no parity), just select this app after connecting to USB and it will use given connection
• Bluetooth connectivity on startup, lists paired devices, so you can choose your modem and connect, you need to pair with your Bluetooth device first from Android Bluetooth Settings
• Voice codec2 mode selection, which allows you to select various codec2 modes from 450 up to 3200 bps.
• Codec2 loopback mode, which records and plays your recorded voice back to test and evaluate different Codec2 modes and speech quality

Suitable radios and modems

• Tested, works:
  • LoRa modem (BT): https://github.com/sh123/esp32_loraprs
  • AFSK1200 PicoAPRS (USB): http://www.db1nto.de/index_en.html
  • AFSK1200/GMSK9600 Kenwood TH-D74A (BT): https://dl1gkk.com/kenwood-th-d74-bluetooth-packet-radio-setup/
• Could work, needs testing:
  • AFSK1200 MicroModem (USB): https://unsigned.io/micromodem
  • AFSK1200/GMSK9600 Mobilinkd TNC3 (BT/USB): https://store.mobilinkd.com/products/mobilinkd-tnc3

Related Projects

• Codec2 codec: https://github.com/drowe67/codec2
• Android Codec2 wrapper code: https://github.com/UstadMobile/Codec2-Android
• Android USB serial: https://github.com/mik3y/usb-serial-for-android
• iOS Codec2 wrapper: https://github.com/Beartooth/codec2-ios

TODO

• Parrot mode, so speech coming from aether will be transmitted back (testing or digirepeating)
• QSO log, voicemail style recording of incoming speech so that incoming transmissions are not missed
• Separate settings to avoid repeated operations
  • Override default USB serial parameters
  • Default Bluetooth device name to connect upon startup
  • Default codec2 bitrate on startup
  • Settings for parrot mode
  • Settings for QSO log