flash update just 1 byte

RE: flash update just 1 byte

Oguz Emre — Wed, 21 Jun 2017 19:05:26 GMT

You're right. Nordic :@

RE: flash update just 1 byte

David — Wed, 21 Jun 2017 16:20:10 GMT

Then you'll have to write your own or modify fstorage or pstorage. Designing your own memory management can be very simple or very complicated depending on your requirements (e.g. how often are you writing data, how big is the data you need to store, whether you can tolerate pulling old data accidentally, ect).

For example, I had a uint32_t variable that I knew would never be 0xFFFFFFFF (if it ever did, the system would break). I reserved a page of flash for this variable.

After boot, I would find the value by searching for the last non-empty value (non 0xFFFFFFFF).

When I wrote a new value, I would write to the first empty address in the page. When I reached the end of the page, I erased the page and started from the beginning again.

My erases were infrequent enough that I would never exceed the 10,000 write/erase cycle limit.

RE: flash update just 1 byte

Oguz Emre — Wed, 21 Jun 2017 15:47:31 GMT

Yes I know that. Fstorage, pstroge use softdevice. but I'm using Nrf without ble

RE: flash update just 1 byte

David — Wed, 21 Jun 2017 15:38:58 GMT

So you have a write address that has already been written to and you want to change the value? You could attempt a second write, but as I said above, it would likely only change the '1's to '0's, you couldn't change '0's to '1's without an erase. That's a physical limitation of flash.

The solution is to move the physical address of the data every time you need to write it. That way you limit your erases. Then the problem is managing where variable actually is.

You could take a look at some of the flash managing libraries from Nordic. See this answer

RE: flash update just 1 byte

Oguz Emre — Wed, 21 Jun 2017 15:06:38 GMT

I am doing it this way and how do we update it? without erase?

RE: flash update just 1 byte

David — Wed, 21 Jun 2017 15:03:39 GMT

Here:

uint32_t* p_Write = (uint32_t*) addressToWriteTo;
        
// Enable write
NRF_NVMC->CONFIG = NVMC_CONFIG_WEN_Wen << NVMC_CONFIG_WEN_Pos;
while (NRF_NVMC->READY == NVMC_READY_READY_Busy){}                  // Wait for flash ready

// Perform write
*p_Write = valueToWrite;
while (NRF_NVMC->READY == NVMC_READY_READY_Busy){}                  // Wait for flash ready

// Disable write
NRF_NVMC->CONFIG = (NVMC_CONFIG_WEN_Ren << NVMC_CONFIG_WEN_Pos);

RE: flash update just 1 byte

Oguz Emre — Wed, 21 Jun 2017 14:54:52 GMT

Thank you for your answer. Can you give me an example?

RE: flash update just 1 byte

David — Wed, 21 Jun 2017 14:41:10 GMT

If the specific address you're writing to is already erased (i.e. its value is 0xFFFFFFFF) you don't need to erase the whole page before the write.

If the address is not erased, you may be able to write to it a second time. The absolute maximum ratings of the nRF51 state that an address can be written to 2 times without an erase. However, I believe you would be you could only change '1's to '0's on the second write.