Calculate available space to use flash data read and write

Question

Hello Nordic Team 
 I am working on nRF52832 MCU, SDK-11. I want to calculate available space so that I can save custom sensors data in chip. 
 According to datasheet we have space 512 KB. Here Bootloader occupied 24 KB, Softdevice occupied 108 KB, Application need at least 100 KB so total will be 232 KB and available space is 280 KB. 
 NOTE: Also this application supports the DFU so we need to reserve some space for that. 
 Questions: 
 1. How much space need to reserve for DFU? 
 2. In above calculation we have 280 KB space left. So, how much space I can use for use for save custom sensors data? 
 3. If you provide any calculation then it will be great. 
 
 Please let me know my question is not clear or you need any more information. 
 Thanks 
 Rajneesh

Einar Thorsrud · Answer

Hi, 
 1. You do not strictly need to reserve room for DFU. The bootloader will use dual bank if there is available flash but will fall back to single bank if there is no additional room. That means that the bootloader would delete the application so that the new application could be written directly to the same location in flash, not needing any temporary flash memory. 
 2. You can use all available flash for sensor data. However, it seems you did not include flash needed for the peer manager (storing BLE bonding information) in your calculation. This uses FDS. Typically, you will use three flash pages for that, but it is configurable (depend on how many bonds you want to be able to store). 
 3. I think your calculations were correct, except for the missing FDS pages for the peer manager. Essentially you need the following: 
 
 MRB (Fixed for a given SoftDevice version) 
 SoftDevice (Fixed for a given SoftDevice version) 
 Application (Variable depending on your application) 
 FDS pages (Configurable in your applications sdk_config.h) 
 Bootloader (including bootloader settings page. Given by the bootloader / SDK version) 
 Any remaining flash can be used as you like.

Calculate available space to use flash data read and write

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