What is the size limitation of the nvm storage in module pycom?

[rolandvs]

What is the size limitation of the nvs function?

Is it not possible to return the amount that is still free?

pycom.nvs_set(key, value)
pycom.nvs_get(key)

[bmarkus]

I do not know but it may depend on fw version. Also no idea whether stored data survives fw update or not. I'm missing methods

• get number of total/used indexes
• get list of keys

Also there are some smaller issues with retrieving data with non existing keys, etc.

[rolandvs]

Well no answer since 3 months. I have tried it myself and filled the lopy by running:

import pycom

pycom.nvs_erase_all()

ii=0
while True:
    try:
        print(ii)
        pycom.nvs_set('loc'+str(ii), ii)
        ii+=1
    except: OSErr as err:
        print(err, ii-1)
        break

It will run and exit with "No space available 613", so locations 0-613 can be used. Every location is filled with its "index number".

pycom.nvs_get('loc614') will return None
pycom.nvs_get('loc613') will return 613
pycom.nvs_get('loc612') will return 612, etc.

UPDATING any location:

pycom.nvs_set('loc612', 0x55aa) gives an error:

Will return an error: "OSError no space available"

Removing a single entry:

pycom.nvs_erase('loc613')

If it does not exist the error "KeyError: key not found" is returned

Then when you store the value again:

pycom.nvs_set('loc613', 0x55aa)

But when doing it again you end up with the "OSError: no space available"

So there are 614 locations available where you can store a 32bit value.

There seem to be a BUG when UPDATING an EXISTING parameter when it is filled to the maximum. So there is possible a wrong offset (range) that only is visible when all of the memory is used.

It would be a nice feature to know the begin and end of the flash "NVM" storage space to calculate a checksum to see if there is no corruption of the flash.

Also a function to get a list of all the names of the parameters would be nice.