@ tronicgr: why did you set the E fuse to the following value?
L 0xFF <- OK
H 0xD8 <- OK
E 0xCB <- WHY?
this setting means that BROWN OUT DETECTION is activated at 2.6V
have a look: http://www.engbedded.com/fusecalc
voltage via USB will always be at 5V, so why is BOD enabled? and why 2.6V? is it necessary?
if you disable BOD (value = CF / FF) you can save some more current.
also remove the LED and the voltage regulator from the "pro micro pcb".
thats almost the same procedure as for the 328P boards: https://andreasrohner.at/posts/Electron ... nsumption/
some hints from the Atmega32u4 datasheet:
If the Brown-out Detector is enabled by the BODLEVEL Fuses, it will be enabled in all sleep modes, and hence, always consume
. In the deeper sleep modes, this will contribute significantly to the total current consumption.
Preventing EEPROM Corruption
During periods of low VCC, the EEPROM data can be corrupted because the supply voltage is too low for the
CPU and the EEPROM to operate properly. These issues are the same as for board level systems using
EEPROM, and the same design solutions should be applied.
An EEPROM data corruption can be caused by two situations when the voltage is too low. First, a regular write
sequence to the EEPROM requires a minimum voltage to operate correctly. Secondly, the CPU itself can
execute instructions incorrectly, if the supply voltage is too low.
EEPROM data corruption can easily be avoided by following this design recommendation:
Keep the AVR RESET active (low) during periods of insufficient power supply voltage. This can be done by
enabling the internal Brown-out Detector (BOD). If the detection level of the internal BOD does not match the
needed detection level, an external low VCC reset Protection circuit can be used. If a reset occurs while a write
operation is in progress, the write operation will be completed provided that the power supply voltage is