XDR-I2C

XDR-I2C is a modification of the Sony XDR-F1HD radio tuner.

Warning: This write-up is provided as is. Do everything on your own responsibility! There’s always a risk of a permanent damage to your tuner! Always unplug the power cord and use a properly grounded soldering iron during the modification.

Features

  • Tuner control with a computer.
  • Wide frequency tuning range (from 60 to 130 MHz).
  • Tuning steps: 1 kHz (LW/MW/SW), 5 kHz (VHF).
  • Fixed or adaptive digital IF bandwidth.
  • Precise signal level meter and squelch function.
  • AM or FM demodulation on any frequency.
  • RDS fast PI mode and error correction.
  • Selectable de-emphasis and AGC threshold.
  • Digital alignment of the antenna circuit.
  • RF and IF +6dB gain boost.

HD radio is NOT supported!

What’s needed?

  • Sony XDR-F1HD tuner.
  • Computer with a USB port.
  • Seeeduino board (switched to 3.3V operation).
  • Mini-USB cable, some wires, resistors and a transistor.

See also the XDR-S10HDiP modification write-up.

Connections

The following write-up assumes stock controller and Seeeduino co-existence. If you are interested in an extended modification, click here

Switch the Seeeduino board to 3.3V mode. GND, SDA, SCL and RDS are connected directly to the Seeeduino board. The RESET line is used to block XDR-F1HD’s stock controller CPU while using this modification and requires a transistor. Do not connect the RESET line directly! Use a typical low power n-mosfet transistor, like BS170. It is connected as a key: source to JW29 (GND)drain to RESET (JW28) and gate to digital pin 4 in Seeeduino.

Connections
GND JW29
Analog PIN 4 JW12 (I²C SDA)
Analog PIN 5 JW13 (I²C SCL)
Digital PIN 2 JW16 (RDS)
Digital PIN 4 BS170 gate  
BS170 drain JW28 (RESET)
BS170 source JW29 (GND)
JW25 ↔ 150 kΩ resistor ↔  JW21  
optional:
Digital PIN 3 ↔ 200 Ω resistor ↔  IR LED (+)
GND IR LED (-)

IR diode can be optionally used for automatic tuner power up. If you don’t connect it, you will have to turn on XDR-F1HD manually every time before starting up the software.

xdr-mod-connections

Don’t forget to toggle Seeeduino from 5V to 3.3V operation (mechanical switch on the board). Also consider adding a small fan because XDR-F1HD runs very hot. High temperatures always reduce the lifetime of electronic components.

When the Seeeduino board is unpowered (e.g. a USB cable is disconnected or the computer is powered down), it blocks the I²C bus and tuner will be stuck on a flashing WAIT message. If you want to use modified XDR-F1HD without a computer, connect the internal 10.5V voltage (easily accessible via JW3 jumper) to the Seeeduino’s DC jack pin. Feeding the voltage though DC jack and USB simultaneously results in a thing called USB back-powering. This is a violation of the USB specification and should be avoided. If you want to be 100% safe, disconnect the jack while using USB.

Need an inspiration? Check more pictures of modified tuners.

Source code

Latest version: 2020-02-21 (ZIP). It is compatible with XDR-GTK v1.0 and v1.1.

The development version is hosted on a GitHub repository.

Arduino IDE and drivers

Download the Arduino IDE. Install drivers for the Seeeduino board, which are available in drivers → FTDI USB Drivers directory.

Run the Arduino IDE, choose Tools → Board → Arduino Duemilanove w/ ATMega 328. Open xdr-i2c.ino file and upload it to the Seeeduino board. Mak sure to select correct serial port. Check USB Serial Port device COM number in the Windows Device Manager.

Starting the modification

If you don’t have an IR led, you’ll have to turn on XDR-F1HD manually using the power button. Follow instructions from XDR-GTK page. See the Antenna input alignment paragraph below to fine tune your tuner sensitivity.
Note: When the XDR-I2C is running, XDR-F1HD’s display is dimmed.

Commands

All commands consist of one letter, data and are ended with end-line ASCII character.

  • x – start the controller
  • T – tune to a frequency [kHz]
    T87500 – tune at 87.500 MHz
    The controller will return a frequency, possibly rounded depending on the available tuning step.
  • F – IF digital filter bandwidth (0-15 FM, 16-30 AM, negative number – adaptive bandwidth)
  • F0 – set the narrowest FM filter bandwidth (55 kHz)
    F15 – set the widest FM filter bandwidth (309 kHz)
    F-1 – set adaptive bandwidth
  • A – AGC threshold level
    A0 – highest
    A1 – high
    A2 – medium
    A3 – low
  • D – de-emphasis mode
    D0 – 50 µs
    D1 – 75 µs
    D2 – off
  • M – demodulation mode
    M0 – FM
    M1 – AM
  • G – RF/IF gain boost
    G00 – RF and IF normal gain
    G10 – RF +6 dB gain
    G01 – IF +6 dB gain
    G11 – RF and IF +6 dB gain
  • V – antenna circuit tuning voltage
    V0 – set minimal voltage

    V127 – set maximal voltage
  • – spectral scan, reads signal levels from a desired frequency range (experimental!)
    Sa87500 
    – set start frequency [kHz]
    Sb108000 – set end frequency [kHz]
    Sc100 – set step [kHz]
    Sf3 – set filter
    Sz – set antenna
    – perform the spectral scan
    Sm – like above, but multiple times (continuous)
  • Y – audio volume
    Y0 – mute

    Y100 – set highest volume
  • Q – squelch threshold level
    Q0 – squelch off
    Q10 – squelch at 10 dBf
    Q-1 – stereo squelch
  • Z – antenna switch
    Z0 – set high state on digital pin 8
    Z1 – set high state on digital pin 9
    Z2 – set high state on digital pin 10
    Z3 – set high state on digital pin 11
  • C – antenna rotator
    C0 – set low state on digital pin 6 (CW) and 7 (CCW)
    C1 – set high state only on digital pin 6 (CW)
    C2 – set high state only on digital pin 7 (CCW)
  • X – shutdown the tuner

Antenna input alignment

Each tuner requires an individual alignment of the antenna circuit. XDR-I2C source code contains values optimal for my unit, which will reduce the sensitivity of your tuner. You can align the tuner using:

  • a signal generator,
  • FM stations with stable signal levels.

The user interface XDR-GTK has an antenna input alignment slider, which can be enabled in settings (Antenna tab). Find out a value that provides the best signal level for a given frequency. Use an antenna attenuator for a very strong signals (70-80 dBf or more), as they may be clipped with the tuner AGC.

Write down optimal values, change them in the source code (align.ino file, you can modify or add more frequency ranges) and re-upload XDR-I2C to the Seeeduino board with the Arduino IDE. Keep your modified file for future firmware updates!