NUCLEO L496ZG - Needing to retain a few variables on reset

Mbed OS
1

The device I’m working on needs to be able to save user settings between resets (power still connected at minimum / power disconnected preferred)

I am actually using a NUCLEO L4A6ZG but MBED Studio doesn’t work with it so I program based on NUCLEO L496ZG (I know that this works fine)

Currently there are 3 bool, 6 uint23_t, and 4 uint16_t variables but more may be added later
(These are in a combination of structs and individual variables but can be combined or separated as needed for saving)

I have already looked into KVStore and NVStore:
-KVStore always returns NULL values even with the example code provided by MBED
-NVStore is not recognized by the compiler (I have to use MBED-os version 5.15.0 due to a few already developed elements that are required and already work perfectly

I appreciate any help that can be given,
Thanks

2

Hi there,

ye, the NVS was replaced by the KVS

Simple example below works on Nucleo F446RE.

#include "mbed.h"
#include "KVStore.h"
#include "kvstore_global_api.h"

int main(){
    printf("Simple KVStore test!\n");
    ThisThread::sleep_for(2s);
    int res = MBED_ERROR_NOT_READY;
    char kv_key[] = {"/kv/key"};
    char kv_value[10];
    char str[10];
    kv_info_t info;

    kv_get_info(kv_key, &info);
    printf("kv_get_info key: %s\n", kv_key);
    printf("kv_get_info info - size: %u, flags: %lu\n", info.size, info.flags);

    res = kv_get(kv_key, kv_value, info.size, 0);
    if(res == MBED_SUCCESS) printf("Stored value [%s]!\n", kv_value);
    else printf("No value\n");
    
    printf("Place a new value to terminal!\n");
    scanf("%10s",str); 
    printf("Your value is %s!\n", str);
    kv_set(kv_key, str, strlen(str), 0);
    printf("Now restart your board - Program end!\n");
}

BR, Jan

3

I just ran that code on my NUCLEO L4A6ZG and every time I restart at the end it says “No value”

However this example code at least doesn’t cause segmentation errors or core dumps like the other example code I have.

4

Ok, just for sure. Did you try to add a value via serial terminal?

For me it looks like this.

First run:

Simple KVStore test!
kv_get_info key: /kv/key
kv_get_info info - size: 134223333, flags: 536871912
No value
Place a new value to terminal!
Hello
Your value is Hello!
Now restart your board - Program end!

“Hello” is my input.

Second run:

Simple KVStore test!
kv_get_info key: /kv/key
kv_get_info info - size: 5, flags: 0
Stored value [Hello]!
Place a new value to terminal!
...

BR, Jan

5

Yea when i type in my message it does confirm what I enter (The “Your value is ____” line shows correctly)

but when I reset after that it says no value and the size is 134268000 and flags is 134238455

KVS may not work on my specific board?

6

No specific board but probably for the whole L4 series. I tested it on my L432KC and I have similar/same result. Maybe different settings.

BR, Jan

7

Ok, just try to add

{
    "target_overrides": {
        "*": {
            "target.components_add": ["FLASHIAP"]
        }
    }
}

to the mbed_app.json

BR, Jan

8

Thanks for your help. Ill try those suggestions for the text based things i need to save. But for some reason when I downgraded to os version 5.14.0 nvstore is working now after I add the path to nvstore.h