can't connect to hoverboard stm32f103rct6

[odometrs]

Hi! I want to connect to old hoverboard but  I can't make connection to mcu. I don't have idea why. I try a lot things but nothing worked. The chip is stm32f103rct6. 

10:20:01 : UR connection mode is defined with the HWrst reset mode
10:20:01 : ST-LINK SN : B55B5A1A000000009532F001
10:20:01 : ST-LINK FW : V2J43S7
10:20:01 : Board : --
10:20:01 : Voltage : 3.25V
10:20:01 : Error: No STM32 target found! If your product embeds Debug Authentication, please perform a discovery using Debug Authentication

[Tesla DeLorean]

Unfortunately "I try a lot things but nothing worked" tells us nothing. Enumerate them, and what you observed / learned.

If the device doesn't connect, it could be protected, unpowered, or you are connected to the wrong pins.

If the SWD/JTAG methods don't work, perhaps try the system loader via the USART methods

[odometrs]

Thank you for answer. I tried both SWD and JTAG methods, I checked wireing in st link v2 pcb board. USART method I don't realy understant what i need to do. Do i need another hardware for the USART method?

[Tesla DeLorean]

Depend if it exports a serial port else where. Assuming it does not you'd need a USB-to-CMOS Serial adapter (ie SiLabs or FTDI type dongle), connecting to PA9 / PA10 pins of the STM32F1, and you resetting with BOOT0 pin pulled high.  See App Notes AN2606 and AN3155, serial connectivity via STM32 Cube Programmer.

For SWD common ground, SWDIO, SWCLK and NRST pin, and 3V3 for the ST-LINK's VTarget pin

[odometrs]

Can I use arduino uno for USB-to-CMOS Serial adapter? And I don't get it what I need to do with NRST pin? 

[odometrs]

PA9 and PA10 is in use. I can unsolder them and then connect them to TX and RX is it correct?

[Tesla DeLorean]

Well NRST (Reset Open-Collector, Active Low) is a) what initiates System Loader entry when the BOOTx pins are set appropriately, and b) lets "Connect Under Reset" methods in the debugger/programmer manifest the "reset" of which they speak..

If PA9 / PA10 are in use, by what? Some serial connection or header you can access? Suggest you start sketching out the circuit and connectivity to the STM32F1 in this circuit.