Reader's note: These instructions are specifically for Mac OSX (I was running Catalina). I'm currently trying to port over everything onto my linux computer, but I am running into compile issues there.

Since I've decided it was time to actually learn how to write embedded code, I decided the best thing to do was to start with this free STM32 Discovery kit, which I got for free after attending a conference. It's neat because this board is packed to the brim with sensors, and also includes a WiFi and BLE chip. I only which it had a cell module too, but nothing's perfect.

It's easy to get started with this board because STM32 provides the STM32CubeMX application, which generates code for you automatically. The first thing I wanted to do was to get the USB port working so that I could write serial logs. This was pretty easy to do by following this setup here: https://www.youtube.com/watch?v=AYICE0gU-Sg. Of course, there were some minor differences because the board from that video was different from this one. You can see exactly what by opening the .ioc file in my repo https://github.com/simjxu/stm32_discovery (as of commit hash 1798e96db2c7153ad87412712790d49240252aee).

From there, code was generated. I opted to use the VS Code plugin called "PlatformIO" to help build and read from terminal. The code generated from CubeMX actually had some compile errors when I tried to follow the tutorial. Turns out, it didn't like that a couple of the functions had a mismatched type in the last argument. It was expecting uint16t, but you can see a uint32t.

USBD_StatusTypeDef USBD_LL_Transmit(USBD_HandleTypeDef *pdev, uint8_t ep_addr,
                                    uint8_t *pbuf, uint32_t size);

USBD_StatusTypeDef USBD_LL_PrepareReceive(USBD_HandleTypeDef *pdev, uint8_t ep_addr,
                                          uint8_t *pbuf, uint32_t size);

I edited to say uint16t, and compilations ended up happening successfully, but for some reason this switched back to uint32t, but with no issues compiling after that point... So I'm not sure what's happening here. Nevertheless, I was able to start printing my helloworld over serial. Note that both USB connectors need to be connected in order to read off of that port (see picture).

Results:

As a side note, you are also able to compile in C++ code, no problemo. I tried adding in a class, and was able to get it working and printing out (see classtest.h and classtest.cpp).

class FatherProperty {
private:
    static uint8_t propValue[];        // I need to declare this as static, why?
    // static means that there is only one copy of propValue, no matter how many times the class is instantiated

public:
    void getProperty();
};

uint8_t FatherProperty::propValue[]="asdf\n";
void FatherProperty::getProperty() 
{
    int len = sizeof(this->propValue);
    CDC_Transmit_FS(this->propValue,len-1);         // subtract 1 so that it does not include the extra character
}