When I flash an update of my code, does the stored flash data get erased?

[brianreinhold]

I am having problems writing to flash in an older version of s110 using the sd_flash_write() method. The question I have is when I update my code, make a new build, and download the new code to the nRF51822, does the data I have previously written to flash memory also get erased?

I am using Keil. I see that an erase is performed before the download but I don't know if that is just the code or if my previously written data gets erased as well. If the flash data I have written is NOT erased, how do I erase it? Is there a difference between the 'erase' option only and the 'download' option which also erases?

I am using flash to save bonding data. So I need to know the state of the flash when I make a new update (should I clear the bonding information on the central?).

Thanks.

[Hung Bui]

Hi Brian, 
It's depends on the option you selected in Keil Target setup. 

If you choose Erase Full chip, any application data will be erased. If you choose Erase Sectors only the sectors that your application occupies (the firmware) will be erased. 

So if you have stored bond information, and you select Erase Sectors, then bond info  will retain. 

[brianreinhold]

If I select 'Erase Full Chip' does that include SoftDevice as well? So there are three things

1. SoftDevice

2. Application

3. Data persistently stored by the application such as LTKs for bonding

Is that controlled by the programming algorithm? (It was never clear to me what 'programming algorithm' was.)

[Hung Bui]

Yes, correct. If you choose "erase full chip" the softdevice will be erased. 
The algorithm is the Jlink algorithm used by Keil to flash. 
This option is equal to calling nrfjprog.exe of --chiperase or --sectorerase when you do nrfjprog --program.

[brianreinhold]

Okay, How can I erase the stuff I write (my application and data associated with my application) but NOT SoftDevice?

[Hung Bui]

You would need to erase the pages you use manually using nrfjprog, it's because the programmer wouldn't know where your application data is. 
What we usually do is to do a full erase, then flash softdevice then flash application. You can create a .bat file to execute the tasks automatically. 

[brianreinhold]

That's what I was afraid of. I think I had issues flashing SoftDevice via the 'second project' in Keil and eventually I had to go to the nrfConnect tool to flash SoftDevice successfully. That is quite a pain as it's a breach of workflow from the IDE and easy to mess up.

[Hung Bui]

In our SDK example, you can switch between the project (inside one project) to flash the softdevice only. 
Another option you can do is to have a button to erase all application data. So when you hold the button when starting up, the application will erase the data. 
If you have a .bat file to execute nrfjprog command, it will very quick and you don't have to switch to nRF Connect tool. 

[brianreinhold]

I know you can switch the project to do just the flash of SoftDevice. But it appeared to have issues. So I went to nrfConnect. However, I didn't think about the button. That would be an easy way to do it.