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ST-Linkv2 on STM32F3 Discovery

Question asked by krefta.krzysztof on Jun 8, 2015
Latest reply on Jun 9, 2015 by Clive One

I've been using STM32 for quite some time. In work I use full ST-Link v2 isol but, in home as hobbys (and soon startuper) I use stlink on stm32f4 disovery board. I had no problems with it untill today. 
When my external board is fully powered by Disco. (is connected to 3V and GND) everything works. I can flash it, erase etc. 
However when I connect external power supply to external board (which is 3V45) I cannot connect to device. With STM32 utility I get "Can not connect to target" but still I get Device ID, and type but cannot flash it or read memory. 

Questions are:
1) Is it normal?
2) If I get full ST Link v2 (not isol) will it help?