Extra unbricking tip

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I recently had the rare pleasure to accidentally set my chip (328PB) to the wrong clock setting, right after spending hours carefully wiring everything up.   All was working wonderfully well, but I wanted to switch over to the external xtal.  Due to some Atmel process changes, the old high freq, large-swing mode is no longer avail (but I was gonna operate in a valid, not so high 10 MHz range).   With one push of the fuse programming button everything ground to the proverbial halt.  Of course I assumed I could inject a square wave "clock" into the XTAL 1 pin & all would be recoverable (after removing my xtal).  I set up my generator (& used a scope to verify)....but no dice...I tried several different freqs, but the programmer would never connect to the chip.   I thought I might have accidentally selected low freq (as in 32KHz), when I meant to select low power. So I went back & tried injecting 32KHz, 10KHz, 100KHz...still no dice (and I set the programmer to <1/4 of my clock).  

 

After all this time messing around, I was gonna let my hot air out & just swap in a new chip, but had the thought---if I had selected the 32KHz watch xtal, that's nominally a pretty weak signal.  So I hooked up my gen once again,  but turned the amplitude way down. Amazingly the programmer saw the chip the very first try & I was back in business.  Indeed, I had set the fuses to the 32KHz mode.  I don't recall what the injection freq was, but it was at a rather feeble magnitude compared with a full logic swing.  I verified that if I turned the generator voltage  level back up, it would not detect the chip (using Atmel MKII programmer).  At least/last I was able to change the fuse properly & get my xtal humming.

 

https://www.avrfreaks.net/forum/solved-having-trouble-unbrick-attiny861?skey=unbricking

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

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avrcandies wrote:
Due to some Atmel process changes, the old high freq, large-swing [crystal oscillator] mode is no longer avail (but I was gonna operate in a valid, not so high 10 MHz range).
In lieu of a crystal, some resonators are compatible with mega328PB :

https://www.avrfreaks.net/forum/fan-control-prototype-unsure-some-parts-circuit#comment-2088696 by JoniS

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Next step is to verify if this resonator will please the avr and give proper clock.

E: resonator is co-operating, based on PWM signal applied to pins, which is what it is supposed to be.

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"Dare to be naïve." - Buckminster Fuller