AnsweredAssumed Answered

Debugger: Could not stop Cortex-M device

Question asked by Majerle.Tilen on Apr 14, 2015
I've made several custom STM32F4 boards.
Never any problems, until now, when my JLINK detects my board ONLY, if I press reset button before I press detect device in Keil uVision.

When I press download button I got error "Could not stop Cortex-M device".
I have to press reset button the correct time if I want to download to flash.

My hardware looks like from discovery board.

I'm using STM32F411RC.

BOOT0 pin LOW,
VDD pins with 100nF,
VDDA/VREF pin for PLL connected to VDD with 100nF,
2u2 on VCAP, 1.28V measured there. It looks good.

Do you have any idea what could be wrong here? What possibilities are for this error to happen?

I have connected with SWDIO with all SWD pins including RST pin.
JLINK tries to reset board but it is not detected, even with "Connect under reset".