Update firmware with DFU bootloader using compressed image - to increase the possible application size

[AlexKl]

We are using nrf52 SDK on nrf52832 and we want to have the option of updating the firmware. 
Since we know the size of the expected image will be greater then we currently have, we would like to do the DFU update with a compressed image, giving us more space for the firmware. 

Is there any known implementation of decompression, for example LZ4 format, for the DFU bootloader ? 
Or any other way to be able to preserve less space for the image for update ? 

[Jimmywong2003]

hi, you have few options.

1) Using the non-secure bootloader (https://jimmywongiot.com/2021/05/23/non-secure-bootloader-on-nrf52810/)
2) Using the external spi flash approach (https://jimmywongiot.com/2021/06/01/slim-spi-bootloader-on-nrf52-series-for-device-firmware-upgrade/)

for the compress/decompression, I tried LZO.  For the decompression, it requires 

Worst RAM buffer

• Input buffer: IN_LEN
• Output buffer: (IN_LEN + IN_LEN / 16 + 64 + 3)
• Compression: Dictionary table (64KB) – working memory for dictionary + Output buffer
• Decompression: Output buffer

https://github.com/jimmywong2003/LZO-Compression-on-nRF52

Jimmy