UNO R4 WiFi Stack Trace Debug Runtime Errors

The Arduino UNO R4 WiFi uses CmBacktrace to print useful information from the Arm Cortex-M4 processor as serial output when a runtime error occurs. The output includes an

addr2line

In this tutorial, we will show to enable this feature.

Hardware & Software Needed

• Arduino IDE
• Arduino UNO R4 WiFi

View the Runtime Error

To get the runtime error information in the Serial Monitor, follow the steps below:

1. Ensure that a serial connection must be initiated before the error occurs, by calling Serial.begin() in your sketch. You can include this code inside the beginning of the

   setup()

   function:

   Copy
   1Serial.begin(115200);
   2while (!Serial);

2. Connect your UNO R4 WiFi board to your computer.

3. Open the Serial Monitor. Click the

   

   Serial Monitor button in the top-right corner or select Tools > Serial Monitor in the menu bar.

4. If you made any changes to your sketch, click the

   

   Upload button. Otherwise, you can simply press the RESET button on the board.

5. If an exception occurs on the board, information will be displayed in the Serial Monitor.

   

6. Following the "Registers information" table, the type of fault will be specified. You can read more about the types here.

7. The last line includes a command for the

   addr2line

   utility. See Running addr2line for more information.

Generate a Stack Trace

You can use the

addr2line

Note:

addr2line

is not available as a native Windows application, but can be run with Windows Subsystem for Linux (WSL).

The

addr2line

addr2line

To install

addr2line

• Windows (WSL):

  addr2line

  is not available as a native Windows application, but can be run with Windows Subsystem for Linux (WSL). The Ubuntu distribution of Linux is installed by default and should come with

  addr2line

  .
• macOS:

  addr2line

  can be installed with Homebrew by running

  brew install binutils

  in Terminal.
• Linux:

  addr2line

  may already be installed on your system. Otherwise, run

  apt-get install binutils

  in Terminal (Ubuntu, Debian), or see command-not-found.com/addr2line for other distributions.

1. Copy the

addr2line

Command

Windows (WSL):

1. Copy the command from the serial output.
2. Paste the command into a text editor.
3. Replace

   C:

   with

   /mnt/c

   and replace all backslashes (

   \

   ) with forward slashes (

   /

   ).

macOS:

Copy the command from the serial output (no modification required).

Linux:

Copy the command from the serial output (no modification required).

If you don't want to install

addr2line

addr2line

2. Running the

addr2line

Command

Note: The sketch needs to have been compiled on the same computer you are running

addr2line

on.

Windows (WSL):

1. Open Windows Powershell.
2. Type

   Ubuntu

   into Windows Powershell and press Enter.
3. Paste the modified command into Windows Powershell by right-clicking on the window.
4. Press Enter to run the command.

macOS:

1. Open Terminal.
2. Press ⌘ + V to paste the command.
3. Press Enter to run the command.

Linux:

1. Open Terminal.
2. Press Ctrl + ⇧Shift + V to paste the command.
3. Press Enter to run the command.

Optionally, you can add the

-p

3. Reading the

addr2line

Output

By default, the command outputs the following for each function call:

• address: "

  0x00004188

  ", "

  0x0000426e

  ", ... (remove the

  -a

  flag if you don't want to include these)
• function name: "

  _ZN4UART5writeEh

  ", "

  loop

  ", ...
• line number "

  /Users/sebastianwikstrom/Documents/Arduino/ErrorInducer/ErrorInducer.ino:67

  , ...

Follow these steps:

1. Look for the topmost line in the output that's inside your sketch. The number following the path is the line number where the error occurred. For example,

   /Users/username/Documents/Arduino/ErrorInducer/ErrorInducer.ino:67

   indicates that the error occurred on line 67. By reading further down the output, you can step backward through the function calls that were made.

   

2. Open the sketch in Arduino IDE and find the line number from the previous step (the number is displayed to the left of each line).

3. Analyze the row where the error occurred and try to understand what may be triggering the error.

• If you're not sure, use the Serial.println() function to output the values of any variables being used. Then upload the sketch again, and use the serial output to see what the states of those variables were before the error occurred.
• To see from where the function was called, look at the preceding function call in the

  addr2line

  output.

In this example, an out-of-bounds access of the

numbers

while(true)

Additional Instructions

Copy the

addr2line

Command (Board Package)

These instructions replace the instructions in 1. Copy

addr2line

If you want to use the

addr2line

Windows (WSL):

1. Copy the command from the serial output.
2. Paste the command into a text editor.
3. Replace the word

   addr2line

   with

   /mnt/c/Users/User/Appdata/Local/Arduino15/packages/arduino/tools/arm-none-eabi-gcc/7-2017q4/bin/arm-none-eabi-addr2line

4. For the file path after the

   -e

   flag, replace

   C:

   with

   /mnt/c

   and replace all backslashes (

   \

   ) with forward slashes (

   /

   ).

macOS:

1. Copy the command from the serial output.
2. Paste the command into a text editor.
3. Replace the word

   addr2line

   with

   ~/Library/Arduino15/packages/arduino/tools/arm-none-eabi-gcc/7-2017q4/bin/arm-none-eabi-addr2line

   .

Linux:

1. Copy the command from the serial output.
2. Paste the command into a text editor.
3. Replace the word

   addr2line

   with

   .arduino15/packages/arduino/tools/arm-none-eabi-gcc/7-2017q4/bin/arm-none-eabi-addr2line

   .