https://devzone.nordicsemi.com/f/nordic-q-a/21293/crc16-is-checkingHello, I am using nrf51822 and SDK11, dual bank dfu ble, S130, 2.0.0. I made dfu zip file and I modify firmware_crc16 value to the wrong one. And I zip it again. But I can successfully upload with nRF Toolbox DFU. I set the break point in &quot;dfu_init_postvalidateen-USTelligent Community 13Wed, 12 Apr 2017 08:48:29 GMThttps://devzone.nordicsemi.com/thread/83402?ContentTypeID=1Wed, 12 Apr 2017 08:48:29 GMT137ad170-7792-4731-bb38-c0d22fbe4515:e7d78d36-7b3e-45b5-b9ad-37e5ab9b0329Hung Bui<p>The .json is mainly for human eyes, as far as I understand.</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/83404?ContentTypeID=1Tue, 11 Apr 2017 13:44:27 GMT137ad170-7792-4731-bb38-c0d22fbe4515:387f6450-490b-4df8-808e-e29e8bc12d2dWojtek<p>I am not sure what .json is used for - maybe it is used by mobile nRF Connect app? dunno. Anyway, about .dat file structure... Compare it with the .json file content, it should be very similar. If not, i think it might be the same structure as the init packet - check it in documentation of bootloader used in SDK You are using.</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/83403?ContentTypeID=1Tue, 11 Apr 2017 13:34:58 GMT137ad170-7792-4731-bb38-c0d22fbe4515:5877585d-ba13-4947-9bfa-c725739c7edasosse<p>Thank you. I can modify the .dat file and it works fine now. Do u know why json file is included in the zip file? and do u know the format of .dat file? I will try to make a custom script to generate zip file.</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/83401?ContentTypeID=1Tue, 11 Apr 2017 13:11:30 GMT137ad170-7792-4731-bb38-c0d22fbe4515:d09f02ca-d14e-4f20-bf83-14c4351efb41Wojtek<p>Wher did you modify, in .json file? It is not sent to the device. There is a .dat or some other binary (as far as i remember) from where that value is actually taken. You can modify it by some hex editor.</p><div style="clear:both;"></div>