Mbed-os: Mbed startup code should not assume power-on state of device

[NeilMacMullen]

Description

An mbed application may follow a bootloader which itself is based on mbed. This typically occurs when supporting OTA (field-upgrade). In this case, it is likely that a new application will be based upon a newer version of mbed than the version that was used to build the bootloader.

The application code therefore should not assume it has been entered via a power-on or reset state and should take responsibility for re-initialising all hardware state since it can't know what state the bootloader left it in. (In the case that led to this suggestion, the bootloader left the microsecond timer running and the application was only using the low-power timer, meaning that the application was drawing > 6mA when deployed!)

Issue request type

[ ] Question
[x] Enhancement
[ ] Bug

[NeilMacMullen]

Adding @cmonr

[0xc0170]

@NeilMacMullen Can you please leave the issue template as it was (description and issue type sections provided, do not remove). This will help us to parse the text and get proper info for further triaging internally.

[NeilMacMullen]

done

[0xc0170]

cc @ARMmbed/mbed-os-core

[ciarmcom]

Internal Jira reference: https://jira.arm.com/browse/MBOCUSTRIA-117

[ciarmcom]

Thank you for raising this issue. Please note we have updated our policies and
now only defects should be raised directly in GitHub. Going forward questions and
enhancements will be considered in our forums, https://forums.mbed.com/ . If this
issue is still relevant please re-raise it there.
This GitHub issue will now be closed.