Troubleshooting AT90USB1286 - EEPROM

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I have a semi-working printrboard, which uses the AT90USB1286. When I try to erase it via Flip I get this error:

 

Blank check fail at 0x00000

 

The problem with the board is twofold:

 

  1. I want to load the latest firmware on the chip 
  2. If I unplug the printer, a value that should be stored in EEPROM is not set.

 

The value is the z-max travel, and is set by issuing:

 

M211 Z250

M500 (Since Marlin 1.1.0 only changed bytes are written to prolong EEPROM life)

M501(view)

 

My best uneducated guess is that the location in EEPROM where this setting is stored is bad, and the value could change on me while I'm in the middle of a print. But, I doubt Marlin constantly reads from EEPROM, so perhaps this is only an annoyance. I am able to save and it recalls other EEPROM values (ie, z-height offset).

 

I've done a bit of reading and have decided either the lock bit is set, or my chip is bad and I need a new one. Any ideas on what I should try first?

 

I'm leaning towards hooking it up to an AVR programmer (it has an ICSP port) and inspecting the fuse settings. BUT since this EEPROM value keeps reverting, I wonder if the chip itself needs to be replaced.

 

Thanks!

 

John

Last Edited: Thu. Mar 22, 2018 - 02:56 AM