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Load cable for ISP AVR

Discussion in 'Electronic Basics' started by Robert, Jul 6, 2005.

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  1. Robert

    Robert Guest

  2. Dave Garnett

    Dave Garnett Guest

    Hi,
    It might work, but I'd spend the money to get a 'real' Atmel AVRISP. I note
    that the firmware for it seems to get updated with each release of the AVR
    Studio, and I'd wonder about support coming from anyone except Atmel ... My
    experience of third party ISP programmers has been mixed, with particular
    problems at lower voltages.

    And if you add a suitable header to your project you don't need anything
    else to program it - but you'd better read the programming section of the
    datasheet carefully to make sure that you don't get any clashes with your
    logic.

    Dave
     
  3. Rich Webb

    Rich Webb Guest

    Also, the OP should read the datasheet carefully with respect to the
    default chip configuration, since it sounds like he's never programmed
    one before. He should note that the default fuse setting on virgin
    ATmega8 chips is to run from the internal RC oscillator at 1 MHz. This
    frequently (no pun intended (yeah, right)) leads to two problems:

    Trying to program it via ISP with a serial clock faster than 250 KHz may
    (and probably will) fail. This may lead one to believe that the chip is
    faulty, or the ISP programmer is faulty, or the circuit is bad, or ...

    If it does program, one might wonder why the device with the 16 MHz
    crystal is running so damned slow and suspect a faulty chip, or bad
    layout, or ...

    The chip is shipped with those fuse settings so that it can be
    programmed and used in non-time critical applications without any
    external clock or crystal. It's very easy to set the fuses for an
    external reference; also easy to forget to do so.
     
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