3v3 Datalogger modifications.
I have dropped the LadyAda datalogger RTC battery +ve across a 1N4148 silicon diode to give me 2.5v.
I have removed the MCP1700 and bridged Vin and Vout (note the pinout is NOT similar to 78xx series linear regulators
As I am using an Olimex32U4 Leonardo clone, the regulated voltage on the datalogger is only 3.3v when the 5v/3.3v jumper is set and the USB is disconnected. Any SD card must be removed while the boards are connected to USB, otherwise the card will receive 5 volts
. It seems the Due does not have this supply issue.
A rough and ready 2 hour unpowered test does not reveal RTC drift (within 1 minute). I intend to remove the electrolytic capacitors to enable the boards to be readily powered off via a MOSFET.