Kinetis K20DX256VLH7 doesn't work without JTAG/SWD connected.

[atanastulbenski]

Hello,

I'm having quite strange behavior on our custom K20DX256VLH7 based board. When debugging the project everything works fine, but when running from internal flash nothing works.

I'm using:

* OpenSDA debugger found on FRDM-K20D50M board (also tested with Segger JTAG)

* KDS IDE

* Project created through KDS wizard, flash debug configuration.

* Tried few examples provided with KDS/PE.

Tried all possible combinations of pull up/down resistors (10K) on JTAG/SWD pins.

Tried to remove the usage of "printf()" in case of semi-hosting issue, but nothing helps.

What makes things really strange is when run it from the debugger and then manually reset the MCU it works.

Any clue/idea will be appreciated!

Thank You!

[Alice_Yang]

Hello Atanas,

On the FRDM-K20D50M, the chip is k20dx128vlh5, not K20DX256VLH7 .

And i just test on my side , when flash the project in to the board , reset the board , it can work well.

The attachment is my test  project ,create on KDS 2.0 .  and  it light up the RED Led , you can test on your side .

Have a great day,
Alice

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[atanastulbenski]

Hi Alice,

Thank You for your quick reply.

*** On the FRDM-K20D50M, the chip is k20dx128vlh5, not K20DX256VLH7 .

- that is true, but as I mentioned in my original question, we have a problem with K20DX256VLH7 on our custom board. FRDM-K20D50M is used just for debugger found on that board.

Unfortunately we can not test this case on FRDM board since SWD lines (except SWD_TCLK) are always connected to MCU.

So can you confirm/test with K20DX256VLH7 and all SWD lines disconnected from MCU?

Best Regards!

Atanas

[ZhangJennie]

Hi Atanas,

I just tested it on my TWR-K20D72M board, i didn't use on board debugger interface but connect board via external Multilink Universal FX.

what i did:

- downloaded program to board

- power off board. disconnected Multilink Universal FX from Jtag interface. Power on.

- program run well on board.

Have a great day,
Zhang Jun

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