Скачать или смотреть How to Send Data through UART of LM3S811 Microcontroller

Learn how to effectively utilize UART communication in the LM3S811 microcontroller with a step-by-step guide for bare-metal programming.
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Introduction: Understanding UART Communication in LM3S811

If you're venturing into the world of microcontrollers, you might find yourself experimenting with bare-metal programming soon. One common task is sending data via UART, especially with devices like the LM3S811. This microcontroller allows for serial communication, enabling you to send and receive data efficiently.

If you're struggling with your initial attempts to get this set up, you're not alone. In this post, we'll break down how to successfully send data through the UART of the LM3S811, covering the necessary code and configurations.

The Challenge

You might wonder why your attempts to send data through UART didn’t work as expected. Initially, many face the challenge of not seeing any output in the terminal. Let's explore how to fix that.

Breakdown of the Solution

1. Setting Up the Environment

First, ensure you have the necessary tools installed, specifically an ARM cross-compiler environment. You’ll be using:

arm-none-eabi-as for assembling

arm-none-eabi-gcc for compiling

arm-none-eabi-ld for linking

qemu-system-arm for emulating the LM3S811

2. Updating the Code

a. Create the Assembly File (flash.s)

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This assembly file sets up the initial reset vector for the microcontroller.

b. Create the C File (notmain.c)

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The PUT32 function writes a character to the UART data register sequentially.

c. Create the Linker Script (flash.ld)

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This linker script defines where your program sections are placed in memory.

3. Compiling and Linking

Run the following commands in your terminal to compile and create the binary files:

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4. Launching the Emulator

Finally, utilize QEMU to run your compiled binary:

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You should see the message "Have a great day" in the terminal window.

The Solution’s Key Points

Volatility Matters: It’s important to ensure that the UART register you're writing to is defined as volatile. This ensures that the compiler does not optimize accesses to this memory region and skip writing back the values, which can lead to only the last character being sent.

Linker Script Structure: Carefully structuring the linker script ensures that sections like .data are initialized properly at run-time.

Simplified Initialization: While some might prefer using .data and .bss, consider simpler methods that avoid unnecessary complexity.

Conclusion

Getting UART communication to work on the LM3S811 microcontroller may seem daunting at first, but with the right approach, it becomes manageable. By carefully crafting your assembly and C code, utilizing the proper linker scripts, and ensuring correct environment setup, you can successfully send data.

For further exploration into bare-metal programming, consider diving into more complex projects or resources tailored for ARM microcontrollers. Happy coding!