Kits, Microcontrollers, Projects

Arduino-based AVR High Voltage Programmer

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Arduino-based AVR High Voltage Programmer

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Update 12/14/10: The original AVR HV Rescue Shield kit has been replaced by the new and improved HV Rescue Shield 2.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:

  • Upload the HVFuse sketch to the Arduino, available for download here: HVFuse.pde
  • Install the shield and apply +12VDC to the terminals on the left
  • Wait for the red LED to turn on (if it isn’t already)
  • Install the ATmega to be repaired
  • Push the button
  • As soon as the LED turns back on, the AVR is fixed and ready to be put back into service!

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.

hvfuse_fixed.sch

Parts list:

  • An Arduino NG, Diecimila, or compatible
  • A piece of perfboard cut to size
  • Header pins for the Arduino interface (note I had to drill some of the holes to get the headers to fit the nonstandard pin spacing for digital lines 8-13.
  • An LED which indicates when it is ok to insert/remove the AVR
  • A 2N3903 or similar NPN transistor (2N2222, etc.)
  • (20) 1k resistors – these protect the Arduino from short circuits in case something goes wrong
  • A pushbutton switch – this is the ‘go’ button
  • A 28 pin socket for the target AVR

Kits!

A kit version of this project is available.  Visit the HV Rescue Shield 2 product page for more information.

Microcontrollers

Arduino – fix your pin spacing!

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From the Arduino Diecimila page on arduino.cc:

Physical Characteristics

… Note that the distance between digital pins 7 and 8 is 160 mil (0.16″), not an even multiple of the 100 mil spacing of the other pins.

Seriously, why???  This means you can’t drop a protoboard on top of an Arduino without a lot of pain dealing with digital pins 8-13.

Of course now it’s too late to switch because everyone that has designed shields for the Arduno made them to fit the weird offset between pins 7 and 8.

Grumble…

Microcontrollers

I programmed the RSTDISBL fuse.

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AVR microcontrollers use “fuse bits” to set various operational parameters of the device, such as the speed of the internal oscillator or the watchdog timer settings.

Most fuse bits can be set or reset without worry, that is, they can be flashed into one state and then flashed back again using an SPI programmer like the USBTinyISP.

However, some fuse bits are irreversable or at least awkward to change, similar to the code protection bits on a PIC microcontroller.

One example is the RSTDISBL fuse.  This fuse allows bit 6 of PORTC to be used as a general purpose I/O pin instead of the RESET pin.  Well, it turns out that SPI programmers need the RESET pin to flash the device.  (RESET is set as part of the routine to enter serial programming mode.)  Once the RSTDISBL fuse is set, no more SPI flashing is possible.  The only way to recover is with a high voltage programmer like the STK500, which I don’t have.

Too bad I didn’t realize that beforehand.

At least I’m not the only person who has done this before: http://support.atmel.no/bin/customer?=&action=viewKbEntry&id=13

Update: It’s alive!!!  I made a high voltage parallel programmer out of an Arduino, flashed the fuses back again, and the AVR came back to life.  The parallel programming protocol is well documented in the datasheet for the part and pretty straightforward.  I think I’ll transfer the circuit onto a perfboard just in case I ever need to do this again!

Electronics

Coil in a can

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Coil in a can

Last weekend at the Electronics Flea Market I picked up some very strange items, including this one, pictured above.  It’s a tin can that looks very similar to an ordinary soup can, except that it has the following markings on it:

R16-C-28604-15
COIL
QTY.1

NSC.OAKLAND JULY 1953
PRES METH. 2D

Thus far the only information I have learned from the markings are that NSC.OAKLAND stands for the former Oakland Naval Supply Center, closed a decade ago in 1998.  According to Wikipedia, NSC supplied components to the fleet in the Pacific during WWII.  Beyond this I have not been able to find any information.  Presumably this is a replacement part for some piece of obsolete military hardware.  A “coil” is another name for an inductor, a clue that this may be part of a radio system or other high frequency equipment.

After staring at this mysterious object for almost forever (a week) I decided to open it.  Realizing that the can could be full of cold war era hazardous chemicals, munitions, objects under high compression, or nasty sharp edges, I did this very carefully and documented the entire process of discovering the contents.

First, the obvious – opening the can.  Pretty straightforward.

Coil in a can

What’s inside?

Coil in a can

Weird.  Lots of oiled green paper.  Whatever is inside is packed very well, when the can is shaken nothing moves around.

This is the clump of stuff to come out.

Coil in a can

Packing material?  The precursor to styrofoam peanuts?

Below the packing material…

Coil in a can

What’s this?  Vintage dessicant!!!

The last object left in the can looks interesting.  It’s wrapped in oiled green paper and sealed with tape.

Coil in a can

Inside the paper we find this:

Coil in a can

Not a huge surprise – it’s a coil (inductor).  It has a knob or grabby thing on the top and a funny connector on the bottom.  It looks brand new.

Here are a few more pictures.

Coil in a can Coil in a can Coil in a can Coil in a can

The markings are “ARC” and “7270 239 KC”.  ARC might be American Radio Corporation?  239 might be 239 kHz (kilocycles)?  Hard to say, google didn’t turn up anythign interesting.

An impressive amount of stuff was packed into that can!

Coil in a can

This solves the mystery of what’s in the can, but what is it for?  Does anyone know?  I’d love to find out – leave a comment or contact me directly.

Join the resistance.