Create sine wave with microcontroller

Table of Contents

1. Introduction
2. The Hardware Setup
3. Understanding the R2R Resistor Array
4. The Shape of a Sine Wave
5. Introduction to the Software
6. Exploring the Code
7. Putting it All Together: Hardware and Software
8. Using an Oscilloscope to Visualize the Outputs
9. Customization and Experimentation
10. Conclusion

Introduction

In this tutorial, we will explore the fascinating world of creating a sine wave generator using a microcontroller and a hardware setup. While the focus of this tutorial is not on learning new concepts with the microcontroller itself, it will still involve some interesting hardware components and the process of using them to generate a sine wave. We will discuss the R2R resistor array, the shape of a sine wave, the software implementation, and how everything comes together to generate a smooth sine wave output. So let's dive right in and unravel the secrets of this unique project.

2. The Hardware Setup

Before delving into the intricacies of the R2R resistor array and the software, let's first take a look at the hardware setup. In the lower left-hand corner, you will notice a peculiar array of resistors known as the R2R resistor array. This resistor array consists of multiple resistors wired together in a specific configuration. By manipulating the input pins connected to these resistors, we can achieve different voltage outputs on the left side of the circuit, parallel to the capacitor. Currently, we have set up the resistor array with 1k and 2k resistors, resulting in different voltage outputs. However, it is important to note that we are only using three outputs in this configuration due to the limitations of the microcontroller.

3. Understanding the R2R Resistor Array

The R2R resistor network plays a crucial role in generating a sine wave output. By applying different voltages to the input pins of the resistor array, we can achieve varying voltage levels at the output. Each resistor in the array contributes to the overall output voltage, and by manipulating the inputs, we can control the waveform's shape. When a high voltage is applied to a specific resistor, it adds its portion of the output voltage. As the voltage on multiple resistors is increased, the outputs sum up to produce a complete waveform. Conversely, if no voltage is applied to any of the resistors, the output voltage becomes zero. It is important to note that the resolution of the waveform depends on the number of outputs available in the microcontroller. In our case, with the PIC 10F200 microcontroller, we have a limited resolution of only eight steps.

Pros:

• The R2R resistor array provides a simple and cost-effective method to generate varying voltage levels.
• It allows for the creation of custom waveforms with different resolution options.
• The hardware setup is relatively straightforward, making it accessible for beginners.

Cons:

• The resolution of the waveform is limited by the number of available outputs in the microcontroller.
• Using a low impedance load can disrupt the output and require additional circuitry to compensate.

4. The Shape of a Sine Wave

Creating a perfect sine wave directly with the microcontroller is not feasible due to computational limitations. Instead, we rely on a predefined shape that closely resembles a sine wave. Sergey, the creator of this project, manually calculated the values needed to approximate the desired waveform. He used an Excel spreadsheet to determine the voltage values required at each point in the waveform, considering the DAC (digital-to-analog conversion) values. These values are stored in registers, which we will access in the software implementation. The shape of the sine wave is generated by sequentially accessing these registers and outputting the corresponding voltage values.

5. Introduction to the Software

Now that we have a basic understanding of the hardware setup and the shape of the sine wave, let's take a peek into the software aspect of this project. Unlike our previous tutorials, the code for this project is relatively concise, consisting of only 46 lines. The software primarily focuses on populating the registers with the pre-calculated values required for generating the sine wave. The code starts with the initialization and ends with a loop for accessing and incrementing the registers. By looping through the registers, we can access the stored values and provide the desired output.

6. Exploring the Code

To gain a better understanding of the software implementation, let's analyze the code in more detail. The code is divided into sections: setup and main loop. The setup section, lines 1 to 9, initializes the necessary configurations for the microcontroller. Following the setup, the main loop, lines 12 to 36, takes care of writing the pre-calculated values to the registers. Each line within the main loop corresponds to a specific register, and the values are moved into those registers using "move" instructions. The loop, lines 38 to 44, ensures that the registers are accessed sequentially by incrementing the register address.

7. Putting it All Together: Hardware and Software

Now that we have examined both the hardware and software components, it's time to understand how they interact and produce the desired sine wave output. The hardware setup, specifically the R2R resistor array, provides different voltage levels depending on the input voltage configuration. These voltage levels are calculated in the software and stored in registers. The microcontroller then accesses these registers and outputs the corresponding voltage values, resulting in a waveform closely resembling a sine wave. The capacitor connected to the output smoothens the waveform, eliminating the jagged edges and achieving a more refined sine wave output.

8. Using an Oscilloscope to Visualize the Outputs

To gain a visual representation of the generated sine wave, we can utilize an oscilloscope. By connecting the oscilloscope to different points in the circuit, we can observe the effects of the hardware configuration on the waveform. The square waves obtained from the individual resistors can be seen transformed into a more sinusoidal shape as they are added together. As we progress through each stage of the circuit, the waveform becomes smoother and closer to a perfect sine wave. Finally, with the capacitor on the output, we achieve a beautiful sinusoidal waveform similar to what we set out to create.

9. Customization and Experimentation

Once you have a grasp of the basic principles and functionality of the sine wave generator, you can customize and experiment with various parameters to achieve different outcomes. By modifying the resistor values or changing the capacitance, you can alter the frequency, amplitude, and shape of the generated waveform. Additionally, you can explore more advanced techniques such as using op-amps or voltage followers to drive low-impedance loads. The possibilities for customization and experimentation are endless, allowing you to further enhance your understanding and skills in waveform generation.

10. Conclusion

In conclusion, creating a sine wave generator using a microcontroller and a hardware setup offers a unique learning experience. While the microcontroller itself may not introduce new concepts, the combination of hardware components and software implementation presents an intriguing challenge. By utilizing the R2R resistor array, pre-calculated waveform values, and careful programming, we can generate a smooth, low-cost, and customizable sine wave output. We encourage you to explore and experiment with this project, pushing the boundaries of waveform generation and deepening your understanding of microcontroller-based applications.

Highlights

• Generate a sine wave using a microcontroller and hardware setup.
• Utilize the R2R resistor array to achieve varying voltage levels.
• Understand the shape of a sine wave and its approximation using pre-calculated values.
• Explore the concise software implementation for the sine wave generator.
• Visualize the generated waveforms using an oscilloscope.
• Customize and experiment with different parameters for waveform manipulation.
• Gain a hands-on learning experience in microcontroller-based applications.

FAQ

Q: Can I use a different microcontroller with higher resolution for better waveform precision? A: Yes, if you have a microcontroller with more outputs, you can achieve a higher resolution and smoother waveform.

Q: What is the purpose of the capacitor in the circuit? A: The capacitor is used to smooth out the jagged edges of the waveform, resulting in a more refined sine wave output.

Q: Can I connect a low-impedance load directly to the output? A: Connecting a low-impedance load can disrupt the output and require additional circuitry, such as an emitter follower or voltage follower, to overcome impedance mismatch.

Q: How can I modify the parameters to achieve different waveforms? A: You can experiment with different resistor values, capacitance, and software modifications to alter the frequency, amplitude, and shape of the generated waveform.

Q: Is this project suitable for beginners? A: Yes, this project provides a great learning opportunity for beginners due to its simplicity and the exploration of hardware and software aspects.