troubleshooting: how to reset the Olympus OM-D E-M5 if it stops working

introduction

all digital cameras are in reality little computers and like computers, sometimes they develop a glitch in the software which may stop it from working
the simplest thing to try is a soft reboot by turning it off then on again and perhaps taking the battery out and replacing it with a freshly charged one
if the camera turns on but is still playing up then you can do a factory reset using the menu system
if the camera does not turn on, you need to do a “hard” factory reset by either leaving the battery out for 24hrs to drain the internal power supply, or perform a hidden method as outlined below.

this will lose all of your settings including date and time
Power on with [menu] held down
When LCD lights, release [menu]
press the following sequence: [menu], [down] to spanner, [right], [down] to LCD brightness, [right] [info] [ok]
now for the actual reset: Hold [menu]+[ok] together for a few seconds to get the hardware reset screen. [ok] to proceed.