Today I made a few improvements to the AVR HV Rescue Shield documentation, including screenshots of the Arduino sketch in action and a parts list in the assembly instructions.
Expect a FAQ and other stuff in the future as I get user feedback.
Rescue Shield says: Buy me!
This all started last year, when I was playing with an ATmega168 microcontroller and did something silly. I programmed the RSTDISBL fuse bit, which effectively makes it impossible to reflash the chip using an ordinary (serial) programmer.
Instead of giving up and throwing out the “dead” chip, I decided to try to revive it using an obscure high voltage parallel programming mode that isn’t supported by most AVR programmers. Armed with my Arduino and the ATmega168 datasheet, I quickly designed and constructed a programmer using parts I already had on my workbench.
A few hours later, I tested my new programmer and it worked! I revived my “dead” AVR by using spare parts and a few lines of Arduino code. That week I published the schematics and Arduino sketch to the site and called it my Arduino-based AVR High Voltage Programmer.
The response was overwhelming. Since I first posted the design, many people have built their own and used it to fix their “dead” AVR microcontrollers by restoring the fuse bits to sane values. I even received several requests for a PCB and/or kit based on the design, which got me thinking…
Today I’m proud to introduce:
The AVR HV Rescue Shield is a high voltage parallel mode fuse programmer for Atmel AVR microcontrollers.
It currently supports the ATmega48/88/168/328 series and the ATtiny2313. The Rescue Shield does everything my original AVR High Voltage Programmer does, and a lot more. I think the new features make this a really useful tool for anyone working with AVR microcontrollers.
New features include:
I spent considerable time testing each new feature and documenting the Arduino sketch. I hope that you’ll find that the finished product was worth the wait!
To purchase bare PCBs and kits, head over to the AVR HV Rescue Shield product page.
Update 01/02/09: A PCB version of this circuit is in the design stages – some preliminary information is here.
Update 03/11/09: Kits based on this design are now for sale!
Update 12/14/10: The original AVR HV Rescue Shield kit has been replaced by the new and improved HV Rescue Shield 2. Visit the HV Rescue Shield 2 product page for information about the new kit!
As I mentioned earlier this week, I recently “lost” an ATmega168 due to flashing the configuration fuses to disable the RESET pin, without realizing that this makes the device impossible to reflash with SPI. This is particularly frustrating because the device is still 100% functional, just completely deaf to ordinary serial programmers. The only way to recover the device is using what Atmel calls “High Voltage Parallel Programming Mode” which very few programmers support, most importantly, not the USBtinyISP I otherwise love.
Fortunately, my trusty Arduino came to the rescue – I created an Arduino-based AVR programmer that uses the high voltage programming mode and can fix pesky fuses like RSTDISBL.
The Arduino has just enough IO to implement the entire HV protocol plus a “go” button. So far I have only implemented setting LFUSE and HFUSE in software, but there is no reason why the code couldn’t be extended to support chip erase and programming the entire flash as well.
Overview:
The fuse programming process is simple:
Schematic:
Here is an Eagle schematic of the HV Programming shield (click to enlarge):
Update 12/17/08: An observant reader pointed out that there were three errors in the way GND/AGND, AREF and VCC/AVCC were connected on the target AVR in the original schematic. The errors have been fixed and the updated schematic is below. Apologies for any confusion this caused.
Parts list:
A kit version of this project is available. Visit the HV Rescue Shield 2 product page for more information.
