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Re: [avr-gcc-list] avrdude, ATMega128

From: Torsten Mohr
Subject: Re: [avr-gcc-list] avrdude, ATMega128
Date: Sun, 5 Jun 2005 14:45:28 +0200
User-agent: KMail/1.8


> > The supply voltages look ok.
> > PEN is connected to GND.
> This should be VCC. Not even JTAG programming works if this is GND.

i just soldered some additional capacitors to the pcb i made.  Just when i
did this, the wire that held PEN to GND fell off.

Now the program works and i see 2.5 V with the DMM on Port B (as expected)
and i see the expected pattern on port D.

Also, i soldered the additional capacitors off again and now it also works, i
can erase and reprogram the device.

I see two possibilities now:

1. PEN has to be left open (i understand the data sheet differently)

2. when i soldered the SMD capacitors i had bad contact on some pads and
    i fixed that when i soldered the additional capacitors.

Any way, i wonder now why i can erase and reprogram the device even with
PEN left open.  According to the data sheet there is an internal pull-up and
PEN needs to be pulled low during reset.  On the PCB, PEN is now open and
by that pulled high during reset.  I measure 5V at PEN.

Thank you all for your hints.

Best regards,

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