Скачать или смотреть Converting Float Values to String with PIC16F1824 and UART

Learn how to transmit ADC values from a `PIC16F1824` microcontroller using UART, converting them to strings effectively to avoid common pitfalls.
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Converting Float Values to Strings on the PIC16F1824 with UART

Working with microcontrollers can sometimes present unique challenges, particularly when it comes to data type conversions and transmitting those values over communication interfaces like UART. If you're using the PIC16F1824 and trying to send ADC (Analog-to-Digital Converter) values formatted as floating-point strings, you might run into some issues.

In this guide, we'll explore a common problem faced while converting ADC values into float strings and provide a straightforward solution to ensure your data transmits correctly.

The Problem: Issues with printf and sprintf

When attempting to use printf or sprintf to format float values for transmission over UART, users can encounter various errors. For instance:

Warnings about the unknown pointer: Your code might generate warnings indicating that there’s an unknown pointer in the expression.

Memory allocation errors: You may see errors about the inability to find space for variable storage related to your float values.

The typical cause of these problems lies in the limited memory available on microcontrollers compared to standard systems. The PIC16F1824 has modest RAM and Flash memory, which can complicate handling floating-point operations.

Common Attempted Solutions

When faced with these issues, developers often try various methods, including:

Including the standard library for I/O operations.

Changing variable declarations, e.g., using volatile float.

Adjusting buffer sizes for sprintf.

However, these attempts do not always resolve the inherent memory constraints or the specific behaviors of the XC8 compiler.

The Solution: Transmit in Millivolts

After experimenting with the usual methods, one effective workaround emerges: Transmit ADC values in millivolts instead of floats. This approach avoids the complexities of floating-point arithmetic in your embedded application.

Implementation Steps

Read ADC Values: Retrieve the ADC values as you normally would.

Multiply by Conversion Constant: Convert the raw ADC result into a millivolt value. For example, if your resolution is 10 bits and your reference voltage is 5V, the conversion could look as follows:

[[See Video to Reveal this Text or Code Snippet]]

Use Integer Formatting for Transmission: Since you're now working with integer millivolt values, format them using %u within your printf function without the necessity for float conversion:

[[See Video to Reveal this Text or Code Snippet]]

Delay Between Readings: Include a delay in your loop to allow for better spacing in readings:

[[See Video to Reveal this Text or Code Snippet]]

Sample Code

Here’s a simple code snippet reflecting the above solution in a continuous loop:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

Although floating-point arithmetic may seem convenient, the limited resources on microcontrollers such as the PIC16F1824 can lead to complications. By converting your ADC values to millivolts and using simple integers for transmission, you not only sidestep many issues but also make your code more efficient and easier to manage.

We hope this solution helps streamline your project and enhances your PIC16F1824 experience. Happy coding!