HV Rescue Shield now works with the Arduino Mega

HV Rescue Shield works with Arduino Mega!

Thanks to John, of the ATX Hackerspace, who loaned me his Arduino for testing, the HV Rescue Shield now works with the Arduino Mega.

I had to create new byte read/write functions for digital lines 0-7 because they are implemented very “differently” (and I don’t mean that in a good way) in the hardware for the Mega.  If you’re interested in how I did this, check out the new version 2.12 Arduino sketch and the new mega_data_read and mega_data_write functions.

To use the HV Rescue Shield with the Arduino, first download the revised sketch here.  Set the MEGA #define to 1 and compile/upload the sketch to your board.  Make sure you have the Arduino Mega selected in the Arduino Board menu, or the sketch won’t compile.

The Mega has more pin headers than the Rescue Shield, so be sure to install the shield all the way to the left, as shown here:

HV Rescue Shield alignment on the Arduino Mega

If you experience any problems with the HV Rescue Shield and the Arduino Mega, please report them in the support forum.

2 thoughts on “HV Rescue Shield now works with the Arduino Mega”

  1. Duane,

    This shield “rescues” an AVR microcontroller that you stick in one of the sockets.

    AVR’s have “configuration fuses” that control the operation of the part. When working with them it’s easy to accidentally set the fuses to a state that you can’t easily recover from – turning off serial programming capability, for example, renders most inexpensive serial programmers useless in talking to the part. This shield lets you set the fuses on many popular AVR microcontrollers back to whatever value you want, whether it’s the default or some special setting for your circuit.

    It does this by using a special programming mode called “High Voltage Parallel Programming” for the 20 and 28 pin parts, and “High Voltage Serial Programming” for the 8-pin ATtiny devices. This mode is only available on certain AVR programmers, such as the Dragon or STK-500, and not the commonly available cheap ones like the USBTinyISP.

    I hope this helps explain what the HV Rescue Shield does, and why you’d want one. 🙂

  2. OK, I have used another microcontroller but it didn’t have anything like this so – dumb question, but….. what are you rescuing the Arduino from? Does the boot loader get munged or something? Why is a separate device needed?

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