Re: [bug #61169] Bad EEPROM read on mega2560 R3 Arduino board

[Andy Bennett]

Hi,

> I have a mega2560 R3 arduino board. I created a simple sketch 
> from the Arduino
> IDE from file->Examples->EEPROM->eeprom_clear and then modified it to write
> 0x00112233445566778899aabbccddeeff repeating to the eeprom memory. After
> writing out these values and then using avrdude to read them back I get
> 0x00112233445566770011223344556677 instead. I have a custom programmer that
> read back the expected values correctly.
>
> The avrdude command I am using for reading out the eeprom is:
> avrdude -p atmega2560 -c wiring -P COM4 -b115200 -U eeprom:r:dump.bin

I had a similar problem reading/writing from/to a Mega2560 R3 Arduino board 
with a JTAG3ICE in ISP mode. I managed to read the fuses, flash and eeprom 
but couldn't write them reliably.

I managed to flash the arduino bootloader reliably and then flashed the 
rest using that.

The ISP was also very slow, taking ~20 minutes to read or write the image 
from/to flash (which was > 200KiB large).


I'm not sure if there is a problem with these boards. My searching was 
inconclusive as not many people seem to post about using the ISP header and 
lots of people who have this problem solved it by reflashing the 
bootloader.

I tried powering it through the power jack rather than the USB port but 
that didn't seem to help.



How long do your EEPROM reads and writes take?




Best wishes,
@ndy

--
andyjpb@ashurst.eu.org
http://www.ashurst.eu.org/
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