Programming with ArduinoISP erases eeprom

Projects Programming
1

Hello,
I just got a ArduinoISP (http://arduino.cc/en/Main/ArduinoISP) and I successfully used it to program my Uno (menu File/Upload using programmer).
Unfortunately, every time a sketch is uploaded the eeprom is erased and I loose any previously stored data...
Is there a way to prevent this behavior and only write to flash memory?

Thanks,
Daniele

2

There is a fuse setting that controls whether or not EEPROM is erased.

3

See: http://www.engbedded.com/fusecalc

The default settings for fuses for the Uno appear to be:

...
uno.name=Arduino Uno
uno.upload.protocol=arduino
uno.upload.maximum_size=32256
uno.upload.speed=115200
uno.bootloader.low_fuses=0xff
uno.bootloader.high_fuses=0xde
uno.bootloader.extended_fuses=0x05
...

This is in the file "boards.txt" inside your Arduino install (look in the "hardware" folder).

If you change the high fuse line to:

uno.bootloader.high_fuses=0xd6

Then it should work. Play close attention to your typing, getting that byte wrong can make the board unprogrammable.

To repeat, the high fuse should be changed to:

uno.bootloader.high_fuses=0xd6
4

Thank you Nick.
Here's what I did:

  • changed the high_fuses byte to D6;
  • programmed the board via ISP;
  • eeprom got erased, but I thought it was OK since the first upload sets the fuses;
  • programmed the board again.
    And unfortunately the eeprom got cleared again...

Re-reading your post, I noticed that the high_fuses directive seems to be related to the bootloader upload.
So I wrote the bootloader to the board (expected to set fuses), then programmed it via ISP (overwriting the bootloader) and this time eeprom data were still there!

5

Yes that is probably correct. Programming the board (but not the bootloader) may not change the fuses.