I am a newly returned beginner to mbed after 2 1/2 years away from this caper.

I intend writing software for a FRDM KL05 Z and a FRDM KL25Z board. The application is to log temperature and humidity to an SD card. They are to be powered by battery so a low power consumption is required. I can no documentation on the clock settings or peripheral on or off states, all essential for the lowest power consumption. I presume the clock will be going at its rated speed but as to the other conditions the processor is in I dare not hazard a guess. Is there in fact documentation of these things or is that something where we presume the worst and deliberately set the processor state to what we want?

As a follow on the the previous is there documentation of the processor start up code or is that a strict "trade secret"? Is the start up code available that we could better make to suit ourselves? I do note the presence of code to alter the clock source and dividers etc.

Any assistance here will be greatly appreciated.

cheers pete

The power state settings could potentially vary between devices, the manufacturer supplies the initialization code and so it depends whether they have switched things off as default and then powered them up/down when the appropriate constructors/destructors are called or whether they have taken the safe and easy route of powering everything up.

On the couple of parts I've looked into they had turned everything on all the time, my guess is that most if not all of them take that approach.

I don't know of any documentation showing the default settings, you could work it out from the code but the easiest way is probably to write a short program that starts up normally and then reads the appropriate registers and outputs them to a terminal.

The setup code for each part is available in the mbed-dev library (not mbed-src as it would have been 2 1/2 yeas ago, that is depreciated now). If you import that rather than the standard mbed library then you can change the settings as needed to suit your application.

Andy

Thanks for the reply, helpful too.

The manufacturer often has the initial state when they come out of reset in the datasheets. You are right that they could put into code anything they desired whether is is a low power chip of a powerful/versatile chip where the envisages use id for all the peripherals are in use. From my (limited) experience most peripherals are left in their reset state which is usually off.

If that code is indeed available then I can go through it and determine the state on entry to main(). I cannot for the life of me remember the details but I seem to remember that turning everything off is not all that much of a burden.

In the compiler page here on mbed I found nothing at all of any start up code which is what prompted me to ask. Now to put some time into learning a whole lot of stuff.

cheers & thanks