Cheapo HVPP for AVR easy fuse repair suggestions

[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]

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

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]

A friend of mine  teaching young people AVRs

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?

has asked me if I know some cheap affordable easy to repair bricked ATmegas AVRs..

https://mightyohm.com/blog/products/hv-rescue-shield-2-x/

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

There is a big gap between a 12V power source and successfully un-bricking an AVR microcontroller.

[PKTKS]

Thanks for suggestions...

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

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

[Ian.M]

For Arduinos with SMD AVR MCUs, WattsThat's suggestion of using the Adafruit modified ArduinoISP sketch is still viable, hooked up to the target ICSP header. The sketch outputs a clock signal for the target on digital pin 9, so if it fails to program, simply connect that to XTAL1 of the target.  Its probably easiest to simply hold a needle point probe (with 330R in series to prevent disasters) on the end of the load capacitor for the crystal/resonator that goes to XTAL1, as hooking up direct to the SMD MCU pin is rather fiddly.   Hard wire a Nano with the target ICSP cable and extra probe, so you don't have to mess around setting up the programmer end wiring each time you need it. 

For some AVR Arduinos, it would be possible to use HV parallel programming in-circuit, hooking up via the target Arduino's headers. There are only two issues - what's on the /RESET signal, which needs 12V applied for parallel programming, and hooking up to XTAL1, which is used for the parallel programming command pulse.  Unfortunately in-circuit HV parallel programming isn't possible on any Arduino board that includes a clamping diode from /RESET to VCC (e.g. Arduino Uno). You could detect the presence of such a diode by monitoring the /RESET pin voltage.  If the programmer HV output is limited to max 2mA, (allowing 250uA for the MCU, and 700uA through a 10K pullup into the Vcc rail) ,no damage will result if the diode is present as the power LED + its series resistor will keep the 5V rail from rising.   The coupling capacitor from the USB UART IC RTS or DTR to main AVR's /RESET may also be an issue - you may have to cut the PCB jumper that isolates it, and reconnect it after 'fusebusting'.

[Alti]

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

ATMega16/32/162/169/64/128.
If you provide an on board clock generator then it is impossible to brick the chip by fuses.
All of those are are programmable via ISP and debuggable via JTAG with JTAGICE Mk1.

BTW, tell your friend there are ARM Cortex chips available.

[PKTKS]

For Arduinos with SMD AVR MCUs, WattsThat's suggestion of using the Adafruit modified ArduinoISP sketch is still viable, hooked up to the target ICSP header. The sketch outputs a clock signal for the target on digital pin 9, so if it fails to program, simply connect that to XTAL1 of the target.  Its probably easiest to simply hold a needle point probe (with 330R in series to prevent disasters) on the end of the load capacitor for the crystal/resonator that goes to XTAL1, as hooking up direct to the SMD MCU pin is rather fiddly.   Hard wire a Nano with the target ICSP cable and extra probe, so you don't have to mess around setting up the programmer end wiring each time you need it.

That solution of hardwiring something with that sketch may
be enough to bad clock fuses... 

Easily handled by newbies.

Thanks
Paul

[PKTKS]

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

ATMega16/32/162/169/64/128.
If you provide an on board clock generator then it is impossible to brick the chip by fuses.
All of those are are programmable via ISP and debuggable via JTAG with JTAGICE Mk1.

BTW, tell your friend there are ARM Cortex chips available.

AFAIK the ICSP works only if the respective fuse bit allows it..
Which in advance it can not be said

The clock fuse may be easily fixed..
But the other 2 possible bricks of having ICSP disabled and/or RESET pin disabled
would prevent easy fixes..

BTW newbies can't handle the more complex tidbits of ESP32 MCUs.

They are indeed cheaper and having fully compatibles cores in the IDE
but the things required to understand their advantages are advanced
for newbies..   mostly interested in trivial LED and step motors..

light bulb relays..   
The popcorn really..

Paul

[Alti]

ATMega16/32/162/169/64/128.

(..) the other 2 possible bricks of having ICSP disabled and/or RESET pin disabled
would prevent easy fixes..

Nope, the new bricking feature was introduced later. Those chips that I listed neither can have their ICSP disabled (via ICSP), nor do these posses the infamous "Reset pin disabled, f%$#k". These do not even need RESET pin because JTAG does not use RESET pin and you can program them when held under reset if you wanted to.

[amyk]

Give them the datasheet, a breadboard, some wires, and some pushbuttons...

"You break it, you fix it... one bit at a time."

[PKTKS]

For the record...

After a lot of gogglinggg   I found that by 20s there is no silver bullet for that... 

Unique proper advice is by paying a real tool like deprecated
and almost impossible to find today AVR-Dragon or..
the expensive and less powerful AVR-ICE

At least this is a de facto advice by having JTAG and proper graded tools..

Not cheap and not easy to maintain.. at student hands 

Even wonder to buy one for myself..
Paul

[sleemanj]

google AVR fuse doctor

You'll have to build it yourself, I made one some years ago, operation is simply insert chip, press button, fuses get reset, job done.

[Alti]

(..)the expensive and less powerful AVR-ICE

$4

[PKTKS]

google AVR fuse doctor

You'll have to build it yourself, I made one some years ago, operation is simply insert chip, press button, fuses get reset, job done.

Interesting.. but I doubt it will last on student hands...
 
Paul

[PKTKS]

(..)the expensive and less powerful AVR-ICE

$4

This sort of item is more like usbTiny or usbASP....
they already use them and the bad use of external bootloaders
is the main reason for bad fuses ... 

Can not tell this particular one if usbTiny or regular STK500 ....

I have googled for AVR-Dragon...  almost impossible to find old stocks..
It still is the best safe option...

AVR-ICE  available in Farnell and some others..
At least over U$100 plus taxes... to arrive here...

In dozens?  out of the question.

Paul

[Alti]

(..)the expensive and less powerful AVR-ICE

$4

This sort of item is more like usbTiny or usbASP

[PKTKS]

(..)the expensive and less powerful AVR-ICE

$4

This sort of item is more like usbTiny or usbASP

Please en-light me about that 

I can not tell what sort of firmware is bundled inside that AVR...
not without buying it first..

If you already did .. does it emulates full STK500 ?
upgraded versions..

or what else can that 5VUSB  only device do..
besides the claimed JTAG interface..

hopefully compatible with AVR5... at least.

Paul

[Alti]

Please en-light me about that 

I think we all pointed you in the right direction. If the pieces of information provided are not enough then there is no hope for your endeavour.

Good luck!

[PKTKS]

Please en-light me about that 

I think we all pointed you in the right direction. If the pieces of information provided are not enough then there is no hope for your endeavour.

Good luck!

Thanks...

The folk will be using this does not need any luck...
besides fixing some bad student gizmos...

Here this U$4 unit will cost U$10 each due to shipping costs..
on a dozen base...
if  that only does JTAG without HVPP/HVSP

it would be useless..  on the student bench.
The other projects will cost less..

overall bottom line is getting a decent real AVR programmer
for such cases..

I came to that conclusion .. wondering one for me too...
nice to have a spare unit...

Paul

[Doctorandus_P]

There have been a bunch of projects (or copies from each other?) for fuse resetters.

https://html.duckduckgo.com/html?q=AVR+HVP+fuse+resetter

[PKTKS]

There have been a bunch of projects (or copies from each other?) for fuse resetters.

https://html.duckduckgo.com/html?q=AVR+HVP+fuse+resetter

Thanks..   they all need a careful review to weight costs...

ALAS...  DUCKDUCK reminded me the good old days when uncle goog
was not in the top of the hill... and all the net thing was called AltaVista... 

long time ..

better results as well - less clutter

Paul