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Topic: High-voltage programming for AVR chips (Read 5239 times) previous topic - next topic

mrburnette

I think I installed the Digispark code onto an ATtiny85. I did not disable the reset pin. It wasn't required just to make it work.
Only required if you want the 3rd PMW output.


Ray


Coding Badly

There are other signals too, like /WR to write something (eg. a fuse), /OE to read from the chip, and PAGEL to lock data into the page buffer.
HVP must be intended for "high speed" uploading and verification for new processors that have not yet been installed.


nickgammon

Quite possibly. I made no attempts to use it efficiently, after all it would take a lot more time to install the chip into the programmer than the couple of seconds to do the programming. Also you program the flash in words, not bytes, which would have required reworking elsewhere. But if you follow their guidelines for efficiency (and use port manipulation etc.) you could probably flash a new chip in half a second or so.
Please post technical questions on the forum, not by personal message. Thanks!

More info: http://www.gammon.com.au/electronics

abqlewis

HVP must be intended for "high speed" uploading and verification for new processors that have not yet been installed.
Wow, I never thought of that.  So are you saying if I screw up the fuses on an SMD based Arduino (SMD UNO, Pro Mini, Nano, Leonardo et al., etc...) that I may be really screwed?!?!

Is it just that most boards don't give access to the XTAL pins, or would the signal not work if a crystal or resonator were installed.

I was thinking that I could mess around with fuses and just make a HVPP programmer to clean up my victims mistakes.  I may have to rethink that.

Coding Badly

So are you saying if I screw up the fuses...
Don't screw up the fuses.  ;)  There are some clock settings that are very annoying for recovery but disable-reset is the critical one. 

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Is it just that most boards don't give access to the XTAL pins...
That would certainly make HVP difficult.

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...or would the signal not work if a crystal or resonator were installed.
I assume a crystal/resonator and the capacitors would interfere.  I have no idea if they would prevent HVP from working.


nickgammon

Most boards have a resistor and/or a diode between /RESET and VCC. That is going to interfere with any attempts to put 12V on /RESET.

Hence removing the chip (if possible) is probably the only option. I suppose you could cut the trace to /RESET but it might be difficult.
Please post technical questions on the forum, not by personal message. Thanks!

More info: http://www.gammon.com.au/electronics


Paul__B

I assume a crystal/resonator and the capacitors would interfere.  I have no idea if they would prevent HVP from working.
Actually, that is I suspect, the beauty of it - a crystal and capacitors (remember, the capacitors are 22 pF or similar and the crystal not a great deal more) should not interfere with programming, merely slow the transitions a little  - having a HCMOS gate connected to a crystal terminal should easily override the crystal.

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