KW45 Cannot write key using blhost

[Lu888]

As shown in the picture,Fuse 0x20 has not been burned yet， I cannot use blhost to write the key. Why is this？

[luis_maravilla]

Hello

Could you help us confirm if you are using an NXP development board [KW45B41Z-EVK / KW45-LOC] or a custom board? as this will influence in the necessary keys.

Could you help us confirm if you are following any guide or instructions to burn the fuses?

Is the board in ISP mode?

It's important to mention that the method of burning the fuse cannot be reversed. Therefore, it is recommended to modify the fuse with caution.

Best Regards

Luis

[Lu888]

This is our board minimum system design schematic，May I ask if there are any issues with this design？

[Lu888]

Hello
I am using a custom board,This board has not written any keys yet. Currently, we are using the demo key provided by NXP. We would like to test the key writing and NBU firmware upgrade.I am referring to the AN14003 document and reference manual, which uses ISP UART to retrieve and write to fuse.As far as I know, simply pull up the boot config pin and this chip can enter ISP mode,So far, I can use UART to erase and write the flash of the chip,But when writing to fuse, i will encounter the situation shown in the above figure

[luis_maravilla]

Hello,

For reviewing the design on the custom board, I would recommend checking the post The best way to build a PCB first time right with KW45 (Automotive) or K32W1/MCXW71 (IoT/Industrial), this post includes the overall characteristics that a KW45 board must have, including the recommendations in KW45 Hardware Design Recommendations Public

As you mentioned that the keys have not been written yet, you will need to program keys to device; Writing RoTKTH and SB3KDK keys to fuse is essential. And the error in the image shows fail in programming SB3KDK key.

Could you help us confirm if your KW45 custom board its intended for use same as the KW45B41Z-EVK or to a custom end application?

If the intention it's to use the KW45 board with functionality same as the KW45B41Z-EVK, you can use the default SBKDK and RoTKTH keys described in AN14003 Chapter 5.2.1

If you want to use your board for a different custom end application; You will need to generate the custom keys and signed image [process described in chapter 4.2 and in the Jupyter Notebook example]; for custom keys, you must generate the .sb3 file using the .xip file to configure for the custom keys.

Best Regards

Luis