FM RDS Tuner Module for mobile applications using PIC18F46k20

Tuner Module
  • Stereo FM band receiver with RDS decoding for mobile applications.
  • Continuous full RDS data output through RS232: RDS PS, PI, TA/TP/TMC, CT, TMC.
  • Full Radio Text supported: 2×64 characters.
  • Raw TMC data output.
  • Low power operation with two AA (HR6) 1V2 Ni-Mh batteries or power supply.
  • Power input range is +2.4V … +3.0V, 50..60mA without OLED and 80..90mA with OLED.
  • Runs on a PIC18F46K20 at 16 MhZ.
  • Full user control (volume, tune, save preset) with a 5-way micro joystick.
  • Module works as stand-alone without OLED as well.
  • Optional OLED Module 1 with RGB OLED 96×64 pixels shows PS (station name), frequency, TA/TP/TMC, PI, mono/stereo, RT (2 alternating lines of radio text)
  • Serial interface control so the module may be used as a stand-alone module.
  • Analog line stereo output.
  • Antenna connection, suggest use of a 30cm -> 2m wire.


Circuit explanation / Getting started:

Tuner Module

PIC18F46k20 The 18F46k20 offers high speed and low power operation. Well suited for a portable application such as this one.
Si4731/4735 Small tuner chip, includes a RDS demodulator.
OLED OLED Module 1 with 96×64 pixels RGB OLED, Size: 0.95″Needs a +14V Vdd, this is generated by a TPS61080.
Controls With the micro joystick, there are several user controls available. Two for volume (up & down) , tune (left & right) and save preset (short enter.) Zone can be selected on boot:Zone 1 (USA): FM 87,50 -> 108.0 MhZ (75µS setting) To select this zone: left joystick and release on bootup or restart. 

Zone 2 (EURO): FM 87,50 -> 108.0 MhZ (50µS setting): Up joystick.

Zone 3 (JAPAN):  FM 76,0 -> 108.0 MhZ (50µS setting): Right joystick.

Serial interface:  tune up and down (tup & tdn) , set frequency (setxxx.x), save preset (sav), get frequency (get), show basic rds info (rds ), reset module (res)

Preset and zone are stored and reloaded on reboot.

Power The MCP1640 DC-DC step-up converter makes it possible to power the whole circuit from only one AA battery. We have chosen two AA batteries for enhanced stability and endurance. Power input range is +2.4V … +3.0V Do not exceed this!
PCB: We used as much SMD-parts as possible. The PCB from our shop is a double sided and 100% connection tested PCB with plated-through-hole connections. All holes are drilled already. PCB size = 66,50 x 54.90 mm

Schematics: (eagle-files and library can be downloaded below.)

Full resolution image: schematic and pcb (GIF format) Right-click and save as, then open in an image viewer (sch is too large for some browsers.)

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