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Programming SX chip in 3.3V enviroments — Parallax Forums

Programming SX chip in 3.3V enviroments

Jens AltenburgJens Altenburg Posts: 6
edited 2005-01-18 11:52 in General Discussion
Hi,

I try to program the SX28 in a 3.3V environment. I got the error message 'sx-key not found...'.·Could it be possible that the programmer doesn't work with 3.3V power supply?
If I use the SX-Tech-Board, programing works, SX with·3.3V also.

Best regards,

Jens
·

Comments

  • James NewtonJames Newton Posts: 329
    edited 2005-01-17 21:04
    From
    http://www.sxlist.com/techref/parallax/sxkey.htm

    William K Borsum of Dascor says:

    The SX-Key must have five volts input.
    There is a DC-DC on the board but they couldn't/wouldn't tell me specifically what it was for.

    The outputs from the SX-Key (OSC1, 2) must NOT be clamped to anything. Apparently there is a higher voltage required on these pins to tell the target chip that it is in SX-Key/debug/program mode.

    The higher voltage on OSC1 and OSC2 will NOT appear on any other pins of the target chip.

    The five volt supply on the SX-key can be different from the target chip--i.e. the SXkey can run from a five volt supply (single 7805, caps and wall wart= SX-Key-Ring) while the target system runs from its own supply. Only common pins are GND, OSC1, OSC2. The power rails are NOT connected if a different voltage.

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    ---
    James Newton, Host of SXList.com
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    SX FAQ / Code / Tutorials / Documentation:
    http://www.sxlist.com Pick faster!



  • StephenStephen Posts: 53
    edited 2005-01-18 05:22
    The SX-Key requires 5V because it has an onboard charge pump for generating the the 12.5V required to program the SX. The SX-Key firmware [noparse][[/noparse]which controls the charge pump] is designed to run at 5V only.

    There used to be an adapter board sold by Parallax called the SX-Key Ring that sat between the SX-Key and the target board to provide the 5V necessary, while also isolating the SX-Key supply fromt he target board. It may still be available...
  • Ken GraceyKen Gracey Posts: 7,401
    edited 2005-01-18 05:36
    Jens,

    Let me check and see if I have any more of the SX-Key rings in our office at Parallax. We discontinued the product but I bet I can find one.

    I'll contact you off-line if I have success.

    Ken
  • Jens AltenburgJens Altenburg Posts: 6
    edited 2005-01-18 11:52
    Thanks a lot,

    as a workaround I powered the SX-key with a seperate 5V. Now I works very well.

    Best regards,

    Jens
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