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Cheapo HVPP for AVR easy fuse repair suggestions

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PKTKS:
A friend of mine  teaching young people AVRs
has asked me if I know some cheap affordable easy to
repair bricked  ATmegas  AVRs..

I googled for some thing and wonder if RT809 or MiniPro
could be suggested... but I found nothing really suited
to put on students hands..

Any suggestion welcome.. shields, known programmers
anything that could be used for learning people to UNBRICK
bad bricked Atmegas with bad fuses...

Cheap, affordable because these students burn a lot of stuff..

Thanks
Paul

PCB.Wiz:

--- Quote from: PKTKS on December 01, 2021, 06:56:43 pm ---Cheap, affordable because these students burn a lot of stuff..

--- End quote ---

Most easily available would be a PP9 battery and a resistor/zener ?  Use a microswitch so they have to hold it closed to enable 12V
Or, if you can find some ST662 / MAX662 are the technically cleanest 12V generation.
or, if 10V on a light load is ok, a MAX202 or clone RS232 driver has charge pumps to 2x Vcc, curves say  10V~9.75V at < 0.5mA
Or, a diode/capacitor charge pump string, with a zener, and a square wave from a working MCU ?

Addit : here is a link of that last one  https://sites.google.com/site/wayneholder/12-volt-charge-pump

WattsThat:
The typical bricking involves setting the clock fuses incorrectly that results in a part that will not respond to ISP (in circuit serial programming) due to the lack of a clock. All parts ship from the factory set to use the internal RC clock but changing that to another another clock source that doesn’t exist results in a bricked part. HV programming is not required to recover these parts, it just needs a clock.

The easiest and cheapest way to fix this is to use an Uno board with a programming shield that has had simple modification. You create a 1 MHz clock signal using the Uno, the code is already in the ArduinoISP sketch by LadyAda or in various versions on GitHub. Wire the clock to the xtal1 pin of the programmer chip socket and you’re off to the races.
 
Programming shields are available for cheap all over eBay. If you really do need a HV programmer, one of the widely available TL866II units will program the usual AVR parts.

https://learn.adafruit.com/arduino-tips-tricks-and-techniques/arduinoisp

westfw:

--- Quote ---A friend of mine  teaching young people AVRs
--- End quote ---
Which AVRs?  In general, HVPP programmers use a lot of resources in order to be able to handle multiple pinouts of multiple chips (and then HVPP protocols vary from chip-to-chip as well.)  For example, the famous STK500 board has eoght different sockets that you reconfigure with jumper cables, and is overall about us user-friendly as differential equations. :-(

Also: for use by the teacher after kids brick a chip, or for use by the kids themselves?


--- Quote ---has asked me if I know some cheap affordable easy to repair bricked ATmegas AVRs..
--- End quote ---
https://mightyohm.com/blog/products/hv-rescue-shield-2-x/


--- Quote ---Most easily available would be a PP9 battery and a resistor/zener ?  Use a microswitch so they have to hold it closed to enable 12V
--- End quote ---
There is a big gap between a 12V power source and successfully un-bricking an AVR microcontroller.


PKTKS:
Thanks for suggestions...


--- Quote from: westfw on December 02, 2021, 01:01:49 am ---for use by the teacher after kids brick a chip, or for use by the kids themselves?

--- End quote ---

Both. The students brick a lot of UNOs and NANOs ... basic atmega328p
but the SMD versions (which are cheaper and more used) are far more tricky
due to the QFP package.

Solutions should be simple to be handle by absolute newbies..
They need to unbrick when totally screwed fuses prevent them to use
ICSP or other things like other UNOs in breadboard ISPs for DIPs

Solutions involving mounting circuits and bread boarding are not suitable.

First I thought I would find "professional" programmers like RT809
complete with all JIGs could do that using a QFP ZIF adapter..

But I got really confused **IF* the programmer supports these specific
HVPP demands..  TL866II has advantages by having MiniPro under any LINUX..

But so forth i could not determine if the support for bricked ATmegas should work
and what type of adapter should be used..

That AVRRESCUE is great for DIPs but again QFP packages are damn common
.. the students  damage UNOs and NANOs primarily by:
- dead  shorted regulators..
- totally wacko FUSE bits..  impossible to say just clock or also ICSP.
- dead ATmega.. being each day harder to order .. and very expensive in small qts.

Basically I got curious as well how hard could be to find a JIG to HVPP or HVSP
ATmegas using regular professional like programmers..

Got surprised by the lack of ready made solutions.. like adapters w/boosters
and sockets...

Any suggestions still very welcome even to satisfy my own curiosity

Thankx
Paul

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