I recently started studying STM32 microcontrollers (BluePill STM32F103 dev board + ST-link V2 clone). I was wondering if it is possible to add serial communication to ST-Link clone?
From what I understood, those clones are copied form ST-link schematic of official Nucleo boards. The ST-link on Nucleo boards is build with STM32F103CBT6 and pins 12 and 13 (PA_2 and PA_3) are used as TX and RX for serial communication with target microcontroller (and connects to PA_2 and PA_3 pins of targer). See page 65 of official Nucleo documentation
Meanwhile, on ST-link clones those pins are floating and not connected to anything
If I solder 2 wires to pins 12 and 13 of STM32 microcontroller on ST-link clone, would I be able to use those for serial communication with target microcontroller on BluePill board (PA_10 and PA_9 or PA_2 and PA_3)?
UPDATE:
Looks like specifically this ST-link clone is made based on schematics of ST-link on old Discovery boards like this:
In this "configuration" in can't be converted into ST-Link with Serial port feature, since this feature (as Virtual Com port) was added in ST-Link V2.1 on Nucleo boards and has another schematic:
FINAL UPDATE
The topic is not relevant anymore. Recently STMicroelectronics released STLink V3 Mini with very affordable price and same functionality (SWD + VCP) which I bought.
Now it can be bought at about $10
Best Answer
You can download the binary code from the STLINK V2-1 STM32F103CB with ST Link Utility.
You will need a 128K version (103CBT6) of part so normal 64K Blue pill is not big enough. I believe the mARM drop-folder transfer utility probably bloats the V2-1 code to requiring 128K.
I have also heard the firmware USB update will not work because of the USB bootloader having flash protection turned on for the V2-1.
You can get the STLINK V2 with SWO function on a 64K BluePill with the ST Link Utility firmware code download from a STLINK firmware updated Chinese clone.
You can also just cut the 5v runner and take over the connector 5v pins for SWO from uC pin 31 on a Chinese clone. Need to have a fine tip soldering iron and a steady hand to solder the pin 31 connection wire without shorting to adjacent pins.
With the cost of a Nucleo64 ST32F103 with the STLINK V2-1 at less then $11 (Mouser) you have to think about whether it is worth the work.