Troubleshooting UART1_Read_Text() Function Issue with ELSE Condition

Debugging UART Communication in Embedded Systems

Hi everyone! Today, I want to share my recent challenges and solutions related to using UART communication in the microcontroller world. I was working on a project involving a PIC18F67K40 microcontroller and had a curious case where my code struggled to read multi-digit integers via UART. Initially, everything seemed fine when dealing with single-digit values, but as soon as I tried reading values greater than 9, things got a bit tricky.

Summary of the Issue:

My initial setup was meant to print a stored value repeatedly until a new integer was received via UART. This was supposed to work for any integer, but it only worked correctly for values from 0-9. For values greater than 10, it either printed incorrect results or the system would freeze on the first attempt.

Understanding the Original Code

Here’s the crux of the problem based on the code I started with:

// Initialization and continuous reading from UART
while (1) {
    if(UART1_Data_Ready() == 1) {
        UART1_Read_Text(st, ";", 255);
        UART1_Write_Text(st);
        strcpy(str, st);
        UART1_Write_Text("\r\n");
        Delay_ms(1000);
    } else {
        UART1_Write_Text(str);
        UART1_Write_Text("\r\n");
        Delay_ms(1000);
    }
}

In this snippet, the system reads data from UART and checks if the data is ready. If so, it reads text terminated by a semicolon. This data is then copied to another string, str, which is subsequently printed. If no data is ready, it merely reprints the last value.

Identifying the Problem

The problem was two-fold:

1. Termination Character Confusion: The UART1_Read_Text() function awaited a termination character, “;”, which might not have been the right choice for numeric inputs. This could lead to incorrect string termination if the semicolon wasn’t sent correctly or at all.

1. Buffer Overflows and String Operations: The use of strcpy() without checking the length can lead to buffer overflows. Moreover, if the incorrect data (like non-numeric or partial numeric data due to UART communication issues) is copied, it can result in unpredictable behavior.

Solutions to the Problem

1. Adjust UART Settings and Parsing Technique:

To improve reliability, I modified the termination character approach. Instead of waiting for a semicolon, I set the system to read available characters until a newline character is detected, which is a common end-of-line marker in many systems.

1. Buffer Management:

I added checks to ensure that data being copied into str didn’t exceed buffer limits and was properly terminated to avoid overflow or corrupted strings.

1. Improving UART Data Handling:

To handle different values effectively, I adjusted the code to parse integer values directly from the read data and manage them as numerical values rather than strings. This helped in maintaining data integrity and simplified the comparison logic.

Conclusion

The issue underscored the importance of robust data handling in embedded systems, especially when dealing with UART communications. Always ensure that your termination characters, buffer sizes, and data types are appropriate for the task at hand. Hopefully, these insights will help you avoid similar pitfalls in your projects and keep your focus on creating awesome and reliable embedded applications!

By making these changes, I was able to make my system robust and capable of handling integers of any length seamlessly through UART. If you’re working on a similar issue, try considering these points. They might just solve your problem too!