MicroPython Forum (Archive)

Posted: **Wed May 06, 2020 2:34 pm**

Hello,

I have a very simple sleep function which is giving me a memory error, memory allocation failed heap if locked. I have the emergency allocation buffer enabled to get the error information.

function here:

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   def _sleep(t):
            	stm.mem32[stm.PWR + stm.PWR_CSR] |= 1 << 8  # setup wake on rising edge PA0 (PushButton)
            	machine.deepsleep()

I've tested using micropython.heap_lock() and manually doing these and it works. Is there a better way to figure out if you are allocating memory? It's complaining about the stm.mem32 line in particular.

Posted: **Wed May 06, 2020 4:54 pm**

If a number can be represented as a31-bit signed number, then no memory allocation is required. However, if the number doesn't fit, then a memory allocation is required to allocate a large int.

This failure could be happening with either the address or the value. It looks like none of the PWR registers use any of the upper bits so you should be ok on that front.

It looks like stm.PWR has the value 1073770496 (0x40007000). The largest positive value that can be stored in a 31-bit signed number is 0x3FFFFFFF which is what's probably causing the problem.

You should be able to do something like add:

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PWR_CSR = cosnt(stm.PWR + stm.PWR_CSR)

outside your function (the const bit is optional) and then use

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stm.mem32[PWR_CSR]

inside your function to move the memory allocation to where the declaration occurs rather than inside your function.

MicroPython Forum (Archive)

How to know if I am allocating memory?

How to know if I am allocating memory?

Re: How to know if I am allocating memory?