Writing/Erasing the flash with radio on and BLE communication on-going.

[Justin]

I want to erase and write the flash while the BLE communication is going on.

In nRF52832 specifications it is mentioned that the CPU is halted while the NVMC performs write/erase operation. So in this case the BLE communication can fail.

Is there any work around for it? Also are there any examples of NVMC operations?

[Amanda Hsieh]

Hi Justin, 

 If you look at the NVMC — Non-volatile memory controller documentation, you'll see that there is an NVMC->CONFIG register where you can set the flash to read enable, write enable or erase enable. The SoftDevice takes over control of the NVMC when it's running which is why you have to use the sd_flash_page_erase() API when the SoftDevice is active instead of programming the NVMC directly.

When the SoftDevice is enabled, flash operations should be done using the sd_flash_xx api. For writing/erasing to flash, sd_flash_write() / sd_flash_page_erase() should be used. If you try to access the NVMC directly when the SoftDevice is enabled, it will result in a hardfault. See this, this and this link.

To simplifying storing data to flash, the library flash data storage (FDS) and nRF5 SDK v15.3.0: Flash Data Storage Example can be used.

 

-Amanda H.

[Justin]

HI Amanda,

Thanks for your email.

I am not able to understand how FDS works? Where do we give the memory address where I want to start writing? In the input parameter of structures no where we provide memory address.

I am confused when should I use sd_flash*** API and FDS. Also to write few bytes should I go with sd_flash_write() api or FDS?

[Amanda Hsieh]

Hi, 

Justin said:

how FDS works?

Please see this Experimental: Flash Data Storage: 

FDS uses Experimental: Flash Storage as the backend to write to flash. Flash Storage, in turn, relies on the SoftDevice to execute the write. Flash Data Storage supports synchronous read operations and asynchronous writes. 

Justin said:

Where do we give the memory address where I want to start writing

Please see Flash Storage. 

Justin said:

I am confused when should I use sd_flash*** API and FDS.

FDS is a file system, and with sd_flash you just write bytes directly to flash.

you can read about the benefits of FDS here, (the points under "The module has been designed to provide the following benefits: ")

When the SoftDevice is enabled, flash operations should be done using the sd_flash_xx api. For writing to flash, sd_flash_write() should be used. To simplifying storing data to flash, the library flash data storage (FDS) can be used.

 

-Amanda H. 

[Justin]

Hi Amanda,

Thanks for your valuable inputs. I am able to write into flash using Flash Storage.

My question is if the write fails is there any event generated so that it can be retried?

I want to specifically use Experimental Flash Storage or sd_flash_write() API.

[Amanda Hsieh]

Hi,

In Experimental: Flash Storage/Writing data section, you can see how to handle the event return from nrf_fstorage_write().

sd_flash_write() will be communicated to the application with exactly one of the following events:

• NRF_EVT_FLASH_OPERATION_SUCCESS - The command was successfully completed.
• NRF_EVT_FLASH_OPERATION_ERROR - The command could not be started.

-Amanda H.

[Justin]

Amanda Hsieh said:

• NRF_EVT_FLASH_OPERATION_SUCCESS - The command was successfully completed.
• NRF_EVT_FLASH_OPERATION_ERROR - The

Where to add the callbacks for these events in my application? Any code example would be of great help.

[Amanda Hsieh]

Hi Justin,

As my colleagues explained in this post. I suggest you study the fstorage library's handling of that return code.  See line 511 of nrf_fstorage_sd.c and flash_fstorage example in SDK 15.3 for the detail. 

-Amanda H.