Connecting external crystal to NUCLEO-F44RE board

[Lebohang]

Greetings

I have a Nucleo-446RE board which I have attempted to power without the USB cable on a battery system (effectively using the on-board LDO). Knowing that doing this eliminates the MCO from the on-board ST-Link, I have installed a 12MHz, 20ppm crystal with a load capacitance of 16pF. Furthermore, I have taken two 20pF capacitors from a scrap STM32F29I-DISC1 board I have and soldered them onto the Nucleo board. I removed SB50, SB16 and added 0 Ohm SMD resistors on the R35 and R37 traces which were initially vacant.

When I attempt to flash my demo code, I cannot because the core is held in reset. I will disconnect the board and sometimes it will connect, but I still cannot flash any code. I reinstalled the serial bridges and removed the ones which connected the crystal to the MCU, rendering me able to undo the write lock which the MCU somehow sustained. I reverted to the abovememntioned settings as stipulated in one of the user manuals and I am still unable to do anything with the installed crystal. 

I would like to seek assistance in this matter as I do not know how to get the MCU running. 

Thank you in advance.

[Andrew Neil]

When I attempt to flash my demo code, I cannot because the core is held in reset

Have you disconnected the Reset output from STLink to the Target?

With the STLink unpowered, that could be held low ...

[Lebohang]

Hi Andrew

I have removed SB12 (which I assume is the reset output to the target) and tried to connect to the MCU using Stm32CubeProgrammer and attempted to erase the chip. It was intially held under reset, so I disconnected it. Upon pressing the reset button, clicking connect and releasing the reset button, it connected successfully.

 

However, in my attempt to mass erase the chip, I have what seems to be a flash write protection error again.