How to flash bootloader to thingy 52?

[Gova]

I am a newbie for Nordic development boards. I recently bought a thingy 52. When I was searching for how to upload a custom firmware of my own (After disabling few BLE services), I came across this link. OTA-DFU - Generating your own packages

I have installed nrfutil and have generated Private key. But how am I supposed to flash the bootloader? I have only one thingy board in hand.

Once I have my ZIP file, I can do a OTA-DFU with my phone. But please let me know how to flash the bootloader onto the board over the air.

I would be glad if someone can help me. Thanks a ton in advance.

[Bjørn Kvaale]

Edit: I think that should be fine to make a zip file from the hex file. You have two options regarding doing an OTA-DFU, but only one option if you want to upload custom FW to the Thingy. Since you have an nrf52840, you can attach a JTAG cable to the P19 debug out port on the top left of the PDK. Then, attach the other end of the JTAG cable to the Thingy JTAG connector located under the cover to the right of the usb connector. Essentially just follow this guide here. That is the method I normally use for OTA-DFU & Secure DFU of the Thingy.

[Bjørn Kvaale]

Edit: Tip for OTA-DFU of the Nordic Thingy FW (NOT CUSTOM FW!): You can also use the Android or iOS Thingy apps for OTA-DFU of Nordic Thingy FW. Using iTunes and an iPhone 5s worked fine for me, but when I used an HTC Android phone, I got a weird error. This should hopefully not be a problem for different Android phones.

[giova]

Hi, is it possible to upload your own custom firmware using OTA only(no DK) to a device which is flashed with a bootloader and app signed using the Nordic private key?

I tried but I always get error INVALID_OBJECT ...

[Bjørn Kvaale]

Hi Giova, you can upload your own custom firmware over the air, once you have generated a new public & private key & installed your own bootloader (see link). If you know the Nordic private key, it should work to upload custom FW to a device flashed with bootloader & app signed using the Nordic private key. But since you do not know the Nordic private key, this is most likely the reason you are getting this error. You will unfortunately need a DK or an external Segger J-Link to be able to erase & program the Thingy:52 device the first time with your own bootloader.