02: Failed on connect Could not connect to core. 31: No connection to emulator device

[jportici]

It is my first custom board with NXP so it's -very- possible i did something wrong.

I am using a LPC 11u68, I followed the basic connections schematic on page 82 of the datasheet and the schematic from the LPC11u68 board (which is what i'm using to debug)

This is the error i'm getting

02: Failed on connect
Could not connect to core.
31: No connection to emulator device

I had this problem on friday too, but after putting a pullup on the ISP pin i was able to program and debug the board for just one time, to see that it stopped during the startup code, because -of course- i didn't change it so it would run on the internal oscillator.

This was friday at 6 PM so i called it a day, but now i can't program it, period. i can of course program the MCU on the LPCexpresso board.

I already read the other topics and, again, i could program it for one time, used the default settings on LPCExpresso IDE, the MCU on the demo board can still be programmed.

Next thing i'm going to try is to hack a crystal and two capacitors on the board to see if i can get somewhere, after that i'll try the flash magic solution.

Any other ideas?

Oh, yes, the SWD waveforms look good, i don't believe it's an hardware problem

[jportici]

Thank you for your answer, i had already read through the guide and, theoretically, nothing is wrong.

as i said, i was actually able to program the board once and what it think it is happening is

"The image contains code that sets the MCU clocks up "incorrectly"."

(taken from there: Regaining debug access to target MCU)

I'll try the UART bootloader later

[lpcxpresso_supp]

In the first place, check your debug/reset circuitry against:

Design Considerations for Debug 

If you are using the debug probe built in to your LPCXpresso11U68 board to debug your own board, also double check your JP1/JP2 jumper settings are correct for this mode of use.

http://www.nxp.com/files/microcontrollers/doc/support_info/LPCXPRESSO-V2-BOARD-FAMILY-SI.pdf?fasp=1&... 

Regards,

LPCXpresso Support

[jportici]

Boy this is getting interesting.

After about ten seconds of power up, the voltage on the ISP pin drops from target voltage to about 0,6V and then keeps going down to zero.

Resistance between the pin and gnd gets to zero, going back to several megaohms after some thirty seconds that i removed power

happening on three boards out of three. i don't think i destroyed the MCU, i soldered them as i always did for years but i don't understand that behaviour.