Switch branches/tags
Nothing to show
Find file Copy path
Fetching contributors…
Cannot retrieve contributors at this time
197 lines (124 sloc) 10.8 KB

BigBug: Remote printf Tool

Makes debugging embedded projects easy without a debugger!

Download Latest


Sooner or later, every embedded engineer faces microcontrollers' insufficient debugging capabilities. Unless you connect a debugger, or interrupt/stop the execution, it is challenging to collect information about what is going on in the box. You can use a serial port to print messages but this method has limited speed, especially when the environment is noisy. Communication speed also limits how often and how much data you can write using printf().

Imagine you are using a RTOS (real-time operating system) and have many tasks running asynchronously. The best way of debugging on this environment is printing as many messages as possible on function entry, exit, measurement, event handlers, overflow of some timers etc. But every message slows down the system more. You can't realistically send a 10-character sequence on every method entry.

Fortunately, BigBug is here to help! You can tell many things with only 2-letter codes which BigBug translates into human language.

How Can BigBug Help You?

BigBug is a tool for displaying comprehensive debug messages on a PC by sending only 2 letters (plus newline \n) from a microcontroller via serial port (UART). The messages are interpreted on the PC and decoded using a lookup table that is obtained directly from your project's source code. The biggest benefit is keeping the MCU free for real tasks rather than spending time printing long debug messages.

Consider this example:

puts("HE");//@BB[HE] Hello World!

Here you only send HE\n and BigBug prints Hello World! on PC screen.



BigBug can be used on-site, operating on a single UART TX line, supporting any baud-rate. BigBug doesn't send any data to your device currently.

Supported Languages

Virtually any language is supported. BigBug descriptors can be embedded into comments on your program, or can be supplied in a separate text file. All will be scanned by BigBug and the descriptors will be parsed. Descriptor format enables any programming language to send messages to BigBug. Even when you use a language like Python where the comment starts with # instead of //, you can still write BigBug descriptors like #....

Detailed Usage

Where to Start

BigBug works by scanning the source code of your project folder. Let's explain the usage with very basis examples about what to write into your project to enable BigBug.

  1. Download BigBug (and compile yourself if you want), no installation required.
  2. Write BigBug descriptors similar to the given examples, refer to Examples and Descriptor Format sections. Descriptors can be embedded into your source code or list all descriptors into a dedicated txt file in your project folder.
  3. Write your embedded project so that it sends serial port (UART) messages that correspond to your descriptors, refer to Serial Message Format section.
  4. Show your project folder to BigBug by opening project.
  5. Connect BigBug to your device over serial port, selecting a COMx port and proper Baud rate.
  6. Filter the incoming messages, if you need.


  1. No payloads (string literal only).

    The very basic string output function puts() can be used for the simplest message as a string literal.

    puts("HE"); //@BB[HE] Hello World!

    Here BigBug scans this source line and knows the HE shortcode means Hello World!. Whenever it receives HE\n from the serial port, Hello World! will be displayed.

  2. Single payload (replacement type).

    This example shows another example that uses printf() and message has a replacement payload. The 0th payload that is sent by the MCU during runtime will be substituted to {0} and displayed on the screen as i.e. New measurement x=-3.14 or New measurement x=Low.

    printf("Me%i\n", 32);//@BB[Me] New measurement x={0}

    The line above sends Me32\n and 32 is evaluated as 0th payload. Finally, BigBug displays New measurement x=32

  3. Multiple payloads.

    In this example there are 4 payloads (replacement, replacement, explicit enumerated, implicit enumerated) that are appended to the message sent by the MCU.

    //@BB[TM] Time is {0}:{1} {2:(0),(1)AM,(2)PM} and today is {3:Sun,Mon,Tue,Wed,Thu,Fri,Sat}

    The example message descriptor tells BigBug to look for UART messages starting with "TM" letters, then expects 4 payloads, {0} to {3}. First 2 payloads ({0} and {1}) are replacement type and interpreted the same way as 2nd example. Next payload {2} is a enumeration type and gets the enumeration index from MCU and replaces it with the corresponding text from the description.

    Here {2:(0),(1)AM,(2)PM} tells BigBug that this block will be replaced by:

    • "" if 2nd payload value is equal to 0,
    • "AM" if it is 1,
    • "PM" if it is 2.

    3rd payload {3} is also enumerated but it doesn't provide enumeration index numbers. In this case, BigBug will enumerate the items automatically starting from 0. This means {3:Sun,Mon,Tue,Wed,Thu,Fri,Sat} will be replaced by "Sun" if received corresponding payload is 0, "Mon" if 1 and so on.

    An example code line that sends message of this type is given below.

    cout << "TM" << "12" << " " << "34" << " " << "1" << " " << "5" << endl;

    The message above will be displayed as Time is 12:34 AM and today is Fri on BigBug.

Check Example/ folder for an example project

Detailed Reference

Supported Payload Types

  1. String Literal
  2. Replacement payload (numeric or string)
  3. Enumerated payload (Explicit or Implicit)

Descriptor Format

Parts of the descriptor are shown below. (1) is BigBug descriptor tag, (2) is message shortcode, (3) is format string.

    (1)     (3)
    vvv     vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
    @BB[TM] Time is {0}:{1} {2:(0),(1)AM,(2)PM} and today is {3:Sun,Mon,Tue,Wed,Thu,Fri,Sat}

And below are the payload fields. (4) is string literal, (5) is replacement payload, (6) is explicitly enumerated payload and (7) is implicitly enumerated payload.

            (4)                                              (7)
            vvvvvvvv                                         vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
    @BB[TM] Time is {0}:{1} {2:(0),(1)AM,(2)PM} and today is {3:Sun,Mon,Tue,Wed,Thu,Fri,Sat}
                    ^^^     ^^^^^^^^^^^^^^^^^^^
                    (5)                     (6)
  • Supported shortcode characters are ASCII letters only (A-Z, a-z).
  • You don't need to write the same descriptor more than once in a project. You can describe once and use the described format in as many as needed parts of your project.
  • Scanned file types are: txt as mx ada ads adb asm asp au3 bc cln bash sh bsh csh bash_profile bashrc profile bat cmd nt c lex ml mli sml thy cmake cbl cbd cdb cdc cob litcoffee h hpp hxx cpp cxx cc ino cs css d diff patch f for f90 f95 f2k f23 f77 hs lhs las html htm shtml shtm xhtml xht hta ini inf reg url wer iss hex java js jsm jsx ts tsx json jsp kix lsp lisp lua mak m nfo nsi nsh mm pas pp p inc lpr pl pm plx php php3 php4 php5 phps phpt phtml ps ps1 psm1 properties py pyw r s splus rc rb rbw scm smd ss st sql mot srec swift tcl tek tex vb vbs v sv vh svh vhd vhdl xml xaml xsl xslt xsd xul kml svg mxml xsml wsdl xlf xliff xbl sxbl sitemap gml gpx plist yml yaml.
  • You can override the file types by defining FileExtensions under User section in settings.ini file (in BigBug.exe working directory). List format is c cpp hpp etc.

Serial Message Format

Below is an example serial message sent by a microcontroller. (1) is shortcode of the message, (2) payloads and (3) is line terminator. Terminator can be either \n or \r\n.

        (1)        (3)
        vv         vv
        TM12 34 1 5\n

And payloads are shown below with respective index numbers. Separator character is space and values (payloads) can be empty (in this case two consecutive spaces).

          {0}  {2}
          vv    v
        TM12 34 1 5\n
             ^^   ^
            {1}  {3}
  • There is no limit for number of payloads but hundreds of them will impact performance for sure.
  • Space and backslash characters in values should be escaped with backslash (like "\ " or "\\").

Message Display

BigBug is tested under 1MBaud continuous serial data rate and maximum number of displayed (remembered) message lines is limited to 100k by default. User can override that limit by defining MaxDataRows under User section of settings.ini file (in BigBug.exe working directory). Filtering is possible for messages. As an example entering igb into filter box will match message lines containing text BigBug and | character can be used for or'ing the filter conditions e.g. filter1|filter2.


  1. Open a project. BigBug scans every file in the selected folder and every line of them to learn BigBug descriptors. After successfully opening, the number of descriptors found is shown next to the project name. Open a project

    Version 3.1.0+ supports single fle project which is useful when full source code is large or not exposed.

    Open single file project

  2. Connect to serial port (comport)

    Connect to serial COMport

  3. Messages coming from UART will be displayed on the screen.

    Messages incoming

  4. Filter messages to see specific events of interest. Filter is case-insensitive and wildcard by-default. Different filters can be combined by or operator | character.

    Filter messages

  5. Save the received messages to file. To save, port should be closed.

    Save received messages to a file


For simulation/test on PC

Recommended tool: com0com