Can not program device

[Sergy]

Hi,

I have 2 pins that connected to transistors that turn on high-side FETs. One turns on 3.3v for the rest of the system and another one 4v.

When I turn on 3.3v everything is fine, but when I turn on 4v I can not reprogram device anymore in Keil - says Device not found.

4v lines (controlled by P0.05) do not even cross SWCLK or SWDIO lines. What could be the problem?

Device continues to operate properly, just cant do anything with the debugger.

Also eventually after a while i can reprogram the device (after i completely power it off, disconnect JTAG and UART-USB!!!).

Any idea what could be the problem?

Thanks!

[Hung Bui]

Sorry, I am not very familiar with the GSM module, quite surprised that it can get to 2A. I was suspecting that the high peak current can cause voltage drop and then cause the nRF51 to reset.

I assume that you have set the optimization level to 0. Do you have very long track for SWD pins ?

Your issue sounds pretty similar to this one. Could you try to isolate the nRF51 from the rest of the board ?

You can send us your schematic and layout to our support portal (MyPage) for further investigation.