Firefly ZOL BO001 A2 000251 to 000500 power supply enhancement - Zolertia/Resources GitHub Wiki
First batch of Fireflys Rev-A2 has a supply issue it's solved on next production changed a component.
This issue is visible when you connect a external devices (sensors, actuators...) the selected component can not supplied enough current.
If you supply the Firefly over battery holder this issue not affects.
Resolutions:
- Debug the application with external 2xAA battery connected on VBAT pin.
- Change diode placed on Q4 component for this P/N:DB2S20500L
Datasheet
The datasheet is available for download Here