So essentially, you just want to send a jpeg file over a Bluetooth connection, right? Are you trying to send this image from a nrf52dk to a smartphone or vice versa? DFU is for updating the firmware of the device (for example a Nordic Thingy:52). It is not made for transferring other types of data than the firmware of the device. Have you taken a look at this website yet? When they say "firmware image", they do not mean an image like a jpeg file for example. They essentially mean the hex or zip file for performing the device firmware update.
So essentially, you just want to send a jpeg file over a Bluetooth connection, right? Are you trying to send this image from a nrf52dk to a smartphone or vice versa? DFU is for updating the firmware of the device (for example a Nordic Thingy:52). It is not made for transferring other types of data than the firmware of the device. Have you taken a look at this website yet? When they say "firmware image", they do not mean an image like a jpeg file for example. They essentially mean the hex or zip file for performing the device firmware update.
