back

Build your own RDS decoder!
(Contributor: Puskas Barnabas, Hungary )
To run the RDSS0375 and other RDS decoding software you can build your own decoder instead of buying and modifying an existing one. This decoder interface is build using the integrated circuit called TDA7330. You can download a full description of the TDA7330 in pdf format (218 kb). The free Adobe pdf reader can be downloaded here. This IC can produce digital output signals (Cp, DATA) which can be processed by using one of the serial ports of the PC and the stereo composit signal (MPX signal) from your tuner. We connect these output signals to the suitable pins of the serial port over an SN7404 TTL inverter. This is to prevent the port to overload the outputs. Click here to see the circuit diagram. How to draw this circuit? Click here and here. You may use a simple ribbon cable to connect the outputs (Cp, DATA, GND). You have to connect the MPX signal from your tuner and to the MPX input of the interface. Use one-veinted shield cable. The MPX signal can be found in your tuner near the FM demodulator resp. before the stereo decoder circuit. (Here you will have to use an amplifier if the level of the output MPX signal is too low) The circuit can be placed in an external box, in that case you should provide an external 5V power supply (for example use of 4 NiCd (1.2V) battery), or it can be built into the box of the receiver and in this case you could use a 5V power supply but don't forget to pay attention to the correct polarity. Setting it all up: after having built the circuit connect the MPX input to the MPX output of the receiver (which Iíve mentioned above) and connect the outputs (Cp, DATA) to one of the serial ports. (COM2 is recommended, because in this case COM1 will be kept for the mouse) Here I draw your attention that if you use COM2 you will have to use a DB9-DB25 serial converter! Turn on the receiver and tune it to a station with a strong signal and carrying RDS. Before running the software do not forget to set up the suitable port in the .ini file. After you start the software the circuit can do its decoding. Possible mistakes, if it does not work: - The MPX signal is too low. - The configuration of the .ini file is wrong. - Serial port is disabled in the setup. - The received transmitter do not carry RDS. - The circuit has no power. - Short circuit or breaking on the printed circuit. - Incorrect connection. - Your Windows xx is not compatible with the software. (it is strongly recommended to run it under DOS) For futher inquiries have a look at: http://www.btk.ppke.hu/~silvius/rds_eng.htm or mail the author.

back