Hey guys! Ever wanted to dive into the world of 3D printer firmware and get your hands dirty with the nitty-gritty? Well, you're in the right place. Today, we're going to explore how to set up Marlin with CDC (Communication Device Class) in FS (Full Speed) mode on the STM32G0B1RE microcontroller. This might sound like a mouthful, but trust me, we'll break it down into easy-to-digest pieces. Whether you're a seasoned embedded developer or just starting, this guide will walk you through the process step-by-step. Let's get started!

Why Marlin and STM32G0B1RE?

First off, let's talk about why we're even using Marlin and the STM32G0B1RE. Marlin is an incredibly popular open-source firmware for 3D printers. It's highly customizable, supports a wide range of hardware, and has a vibrant community backing it up. This makes it an excellent choice for anyone looking to tinker with their 3D printer's software.

The STM32G0B1RE, on the other hand, is a powerful and cost-effective microcontroller from STMicroelectronics. It's based on the ARM Cortex-M0+ core, which offers a great balance of performance and power efficiency. Plus, it has plenty of peripherals, including USB, which is crucial for our CDC setup. Combining Marlin with the STM32G0B1RE gives you a robust platform for controlling your 3D printer.

Understanding CDC (Communication Device Class)

Now, let's dive into what CDC actually means. CDC is a USB device class that allows devices to communicate over USB using standard communication protocols. In our case, we'll be using the ACM (Abstract Control Model) subclass, which emulates a serial port. This means that your computer will see the STM32G0B1RE as a virtual serial port, allowing you to send commands and receive data just like you would with a traditional serial connection. This is super useful for sending G-code commands to your 3D printer and receiving feedback from it.

FS (Full Speed) Mode

When we talk about FS (Full Speed) mode, we're referring to the USB data transfer rate. Full Speed USB operates at 12 Mbps (Megabits per second), which is plenty fast for most 3D printing applications. While there are faster USB modes like High Speed (480 Mbps), Full Speed is often sufficient and simpler to implement, especially on microcontrollers like the STM32G0B1RE. It strikes a good balance between speed, complexity, and resource usage.

Prerequisites

Before we jump into the configuration, let's make sure you have everything you need:

• STM32G0B1RE Development Board: You'll need a development board with the STM32G0B1RE microcontroller. There are many options available, so pick one that suits your needs and budget.
• STM32CubeIDE: This is the official integrated development environment (IDE) from STMicroelectronics. It's free and includes everything you need to develop, debug, and flash your code.
• Marlin Firmware: Download the latest version of the Marlin firmware from the official GitHub repository.
• USB Cable: A standard USB cable to connect your development board to your computer.
• Computer: Running Windows, macOS, or Linux.

Step-by-Step Configuration

Alright, let's get our hands dirty with the configuration process. Follow these steps carefully, and you'll have Marlin running with CDC in FS mode on your STM32G0B1RE in no time.

Step 1: Setting Up STM32CubeIDE

First, you need to install STM32CubeIDE. Download it from the STMicroelectronics website and follow the installation instructions. Once installed, open STM32CubeIDE and create a new project.

1. Create a New Project:
   • Go to File > New > STM32 Project. A new window will open, asking you to select the target microcontroller.
2. Select the Target Microcontroller:
   • In the target selector, search for STM32G0B1RE. Select it and click Next.
3. Project Name and Location:
   • Give your project a name (e.g., Marlin_STM32G0B1RE) and choose a location to save it. Click Finish.

Step 2: Importing Marlin Firmware

Now that you have a new project, you need to import the Marlin firmware files into it.

1. Locate Marlin Files:
   • Extract the Marlin firmware you downloaded earlier.
2. Copy Marlin Files:
   • Copy all the necessary Marlin files (source files, header files, etc.) into your STM32CubeIDE project directory. A good approach is to create a Marlin folder inside your project and copy the files there.
3. Import Files into STM32CubeIDE:
   • In STM32CubeIDE, right-click on your project in the Project Explorer and select Import > General > File System. Navigate to the Marlin folder in your project directory and select all the files. Click Finish.

Step 3: Configuring USB CDC in STM32CubeIDE

This is where the magic happens. We need to configure the USB peripheral in STM32CubeIDE to operate in CDC mode.

1. Open the .ioc File:
   • In the Project Explorer, double-click on the .ioc file (e.g., Marlin_STM32G0B1RE.ioc) to open the STM32CubeMX configuration tool.
2. Enable USB Peripheral:
   • In the STM32CubeMX configuration tool, go to Connectivity > USB. Set the mode to Communication Device Class (Virtual Port). This will enable the USB peripheral and configure it for CDC operation.
3. Configure Clock Settings:
   • Go to Clock Configuration. Ensure that the clock settings are correct for your STM32G0B1RE board. Typically, you'll want to use the HSE (High-Speed External) oscillator if you have one, or the HSI (High-Speed Internal) oscillator if you don't.
4. Configure Interrupts:
   • Go to NVIC Settings. Enable the USB interrupts. This will allow the microcontroller to handle USB events.
5. Generate Code:
   • Go to Project Manager > Generate Code. This will generate the necessary HAL (Hardware Abstraction Layer) code for the USB peripheral.

Step 4: Modifying Marlin Configuration

Now that we have the USB peripheral configured, we need to modify the Marlin configuration files to use the CDC interface.

1. Locate Configuration.h:
   • In the Marlin firmware, find the Configuration.h file. This file contains the main configuration settings for Marlin.
2. Enable Serial Port:
   • In Configuration.h, find the SERIAL_PORT define and set it to 2 or another available serial port number. This tells Marlin to use the CDC serial port.
3. Define Serial Port Speed:
   • Set the BAUD_RATE define to the desired baud rate (e.g., 115200). This is the speed at which the serial port will communicate.
4. Configure USB Settings:
   • You may need to adjust other USB-related settings in Configuration.h depending on your specific hardware and requirements. Refer to the Marlin documentation for more details.

Step 5: Building and Flashing the Firmware

With the USB peripheral configured and the Marlin configuration modified, it's time to build and flash the firmware to your STM32G0B1RE board.

1. Build the Project:
   • In STM32CubeIDE, go to Project > Build Project. This will compile the Marlin firmware and generate the binary file.
2. Connect the Board:
   • Connect your STM32G0B1RE development board to your computer using the USB cable.
3. Flash the Firmware:
   • In STM32CubeIDE, go to Run > Debug As > STM32 Cortex-M C/C++ Application. This will flash the firmware to your board and start a debugging session.

Step 6: Testing the CDC Connection

Finally, let's test the CDC connection to make sure everything is working as expected.

1. Identify the Serial Port:
   • After flashing the firmware, your computer should recognize the STM32G0B1RE as a virtual serial port. Check your device manager (Windows) or /dev directory (Linux/macOS) to identify the serial port number.
2. Open a Serial Terminal:
   • Open a serial terminal program (e.g., PuTTY, Tera Term, or the Arduino IDE serial monitor). Connect to the serial port at the baud rate you configured in Configuration.h.
3. Send Commands:
   • Send some G-code commands to the serial port (e.g., M115 to get the firmware version). If everything is working correctly, you should see a response from Marlin.

Troubleshooting

If you run into any issues, here are some common problems and their solutions:

• Serial Port Not Detected:
  • Make sure the USB drivers for your STM32G0B1RE board are installed correctly. You may need to download and install them from the STMicroelectronics website.
• Communication Errors:
  • Double-check that the baud rate in your serial terminal matches the baud rate configured in Configuration.h.
• Firmware Not Running:
  • Ensure that the clock settings in STM32CubeMX are correct. Incorrect clock settings can prevent the firmware from running properly.

Conclusion

And there you have it! You've successfully set up Marlin with CDC in FS mode on your STM32G0B1RE microcontroller. This opens up a world of possibilities for customizing and controlling your 3D printer. Remember, this is just the beginning. Feel free to explore the Marlin firmware, experiment with different configurations, and contribute to the Marlin community. Happy printing!