FM-DX Tuner

Multi-plaftorm microcontroller firmware for NXP radio tuners

Copyright (C) 2023-2024 Konrad Kosmatka

This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version.

Work in progress

Firmware is currently compatible with XDR-GTK software and FM-DX Webserver, but the protocol is going to be changed in the future.

Microcontroller support

• AVR (ATmega328P)
• ESP32 (PE5PVB board)
• STM32 (STM32F072 crystal-less)

Tuner support

• TEF668X driver:
  • TEF6686, TEF6687 (V102 and V205)
  • TEF6688, TEF6689 (untested)
  • TEA685X (not recommended)
• SAF7730 driver:
  • XDR-F1HD (extended modification)
• SAF775X driver (highly experimental):
  • Mini SAF775X Radio (from Aliexpress)

Configuration

Check the Config.hpp file and the corresponding tuner configurations.

The directory presets contains predefined configuration files.

Some boards do not work with 400 kHz I2C bus. If you're unable to start the tuner, try lowering the TUNER_I2C_CLOCK value to 100 kHz.

TEF668X configuration

Make sure to set correct TUNER_TEF668X_REF_CLOCK frequency. Wrong frequency value will not stop tuner from working, but the reception will be corrupted.

The PE5PVB board contains a hardware jumper for selection of the clock frequency (keep the default zero value of TUNER_TEF668X_REF_CLOCK).

Arduino AVR boards

TEF668X tuners require 3.3V logic level on the I2C bus, but the AVR based Arduino boards are 5V, which is out of specification for the TEF668X ICs. Because of that, the TUNER_AVR_PULLUP is set by default to false.

Due to the nature of the I2C bus, it is OK to use a microcontroller with 5V logic on a 3.3V I2C bus (during communication, the bus lines are only being pulled down to the ground). Some of the Chinese tuner modules (especially the ones available currently on Aliexpress) already contain pull-up resistors, so the tuner will work out of the box with the default configuration.

If your tuner module does not have the 3.3V I2C pull-ups (SDA/A4 and SCL/A5 is almost 0V), then you need to solder 10 kΩ resistors: one between 3.3V and SDA (A4), and another one between 3.3V and SCL (A5).

TEF668X Headless USB Tuner (STM32)

Firmware dependencies:

• Board: STM32 MCU Based Boards (STM32duino) - download using board manager
• Library: TinyUSB - install manually to the Arduino libraries

During first firmware flashing, short BOOT to 3.3V, plug the USB cable and flash using Arduino IDE (DFU method). Once the firmware is running, it is not necessary to manually short BOOT pin. See tef-bootloader.