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Topic: Programming an ATtiny85 with Arduino Code and Arduino Uno as Programmer (Read 4881 times) previous topic - next topic

Coding Badly


There are two possibilities left...

1. There is a mistake in your wiring.

2. RESET has been disabled.

What happens to the target when you connect a low value resistor (like 220 ohms) from RESET to GND?  Does the target reset?

marian42

The setup works with another single ATtiny.
Connecting a 470 resistor between Reset and GND has no effect.

Coding Badly


Assuming the processor's Vcc is 5 volts, if the pull-up resistor on RESET is 10 K? then a 470 ? resistor from RESET to ground should bring the voltage on RESET to 0.22 volts.  0.1Vcc is the guaranteed low threshold which is 0.50 volts.  In this scenario the 470 ? resistor is guaranteed to reset the processor.

If the pull-up resistor on RESET is 4.7 K? then a 470 ? resistor from RESET to ground should bring the voltage to 0.45 volts.  Still below the threshold.

If the pull-up resistor on RESET is 4230 ? the voltage is 0.5 volts.  The lowest value that still guarantees a reset.

It seems very likely that RESET has been disabled.  To eliminate all doubt, you could try a lower value resistor.  Were I in your shoes, I wouldn't bother.

Tom Carpenter

If the reset is disabled you might want to look at this:
http://www.rickety.us/2010/03/arduino-avr-high-voltage-serial-programmer/

It is an arduino based programmer that allows you to reset the fuse bytes even if the reset pin has been disabled.
~Tom~

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