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Yaesu FT-7900R: RS-232 to PS2 Data Cable Diagram

Discussion in 'General Technical Questions and Answers' started by AD5GG, May 12, 2011.

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  1. AD5GG

    AD5GG Ham Member QRZ Page

    Does anyone have a diagram for the data/programming cables used with software to program these radios? Rather than order a pre-made USB to PS2 cable, I intend to make my own RS-232 to PS2 cable and use a USB to serial converter. I know some of these can act strangely, and I'm prepared for that.

  2. K7MH

    K7MH Ham Member QRZ Page

    Drivers that will work with the USB converter can be a problem. The Prolific drivers seem to be the best.
    Look here for TTL converter info;
    Last edited: May 12, 2011
  3. AD5GG

    AD5GG Ham Member QRZ Page

  4. AD5GG

    AD5GG Ham Member QRZ Page

    Thank you, sir. I'll bear that in mind.
  5. WA9SVD

    WA9SVD Ham Member QRZ Page

    Be aware that "traditional" Serial Port (RS-232) signals are NOT directly compatible with USB Serial signals, at either the signal or circuitry level. There is NO simple cable that will allow the USB to connect to RS-232 or RS-232 to connect to USB without damage to either or BOTH devices.
    An interface from RS-232 to USB may or may NOT function as you wish; it WILL depend upon the software drivers that are designed for interface from the RS-232 to USB interface.
  6. AD5GG

    AD5GG Ham Member QRZ Page

    Thanks for the advice. I'm aware that USB and RS-232 are totally different entities. I wasn't about to plug in my radio direct ;)
    The circuit I found is a level shifter based upon two transistors. I was a little worried about this design, since it draws it's power from the RTS/CTS lines, but it's clamped to 5V with a Zener diode, so I stayed late at work tonight and built it. It works like a charm, both with regular good old RS-232 (DB9) and a USB to serial converter (uses an FDTI USB to serial IC).

    Just thought I'd let you know!

    I bought and used the G4HFQ Radio Programming Software.
  7. AD5GG

    AD5GG Ham Member QRZ Page

    The cable... built on proto-board, using an old mouse cable.
    It's a bit rough (potted with epoxy and covered in heat-shrink tubing) but it works.

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