Better Debugging for Arduino IDE using Software Debugger (Part 2)

This tutorial was written by João Lopes and edited by Sara Santos.

The SerialDebug library created by João Lopes allows you to improve debugging for the Arduino IDE. In this article he’ll show you how to use the simple software debugger of the SerialDebug library that has most functionalities of an hardware debugger.

This is part 2 of a series of articles about the SerialDebug library. You can check all the articles on the links below.

Part 1 – Using debug with levels
Part 2 – Simple Software Debugger (currently reading)
Part 3 – SerialDebugApp

Simple Software Debugger

When I (João) was developing in ESP-IDF (ESP32 native SDK), I used an hardware debugger, using external hardware compatible with JTAG, GDB server and Eclipse CDT. This is a great solution for debugging because I can see the value of variables, set breakpoints (up to 2 for ESP32), run code step by step, and more.

However, until now Arduino IDE doesn’t support hardware debugger. If you’d like to use hardware debugger, you need:

An external hardware (JTAG, Atmel-Ice, etc)
Another IDE (Eclipse, Atmel studio, etc)
Skills to configure and use it

There are simpler solutions, but these are not free, like the MicroStudio. That’s why there are such few people using debugger in Arduino IDE. Most of all debugging in Arduino IDE is done with Serial.print commands.

When I was developing SerialDebug library, I thought how to bring some hardware debugger features to Arduino without the need for extra hardware and skills. The SerialDebug library has a simple software debugger. Let’s take a closer look at its features:

Simple: It’s a simple, but functional debugger. It doesn’t have all features of a real hardware debugger (like the ability to run code step by step).
Software: It’s implemented in software, not in hardware as a real hardware debugger. But it is optimized to reduce memory and overhead of processing. For this reason, this feature in SerialDebug library starts disabled until receiving the command “dbg”.
Debugger: It is a debugger, you can send commands in the Serial Monitor such as:
- Call a function (works if debugger is enabled or disabled)
- Show and change values of global variables (works only if debugger is enabled)
- Add or change watches for global variables (works only if debugger is enabled)

Note: due to program memory limitations, the simple software debugger doesn’t run in low memory boards such as Arduino Uno. But you can try the debugger with this board by disabling DEBUG_MINIMUM mode, just comment line 64 of SerialDebug.h.

How to use Simple Software Debugger

First, follow the steps in Part 1 of this series to install SerialDebug library. Then, open the advanced example. In the File menu, select Examples > SerialDebug > SerialDebug_Advanced.

Then select Avr for Arduino with AVR arch, like Uno, Leonardo and Mega. Or Others for Arduino as Due, MKR, Teensy, Esp8266 and Esp32. For this post, we use ESP32 board and the example in the “Others” directory.

The following code should open:

////////
// Libraries Arduino
//
// Library: SerialDebug - Improved serial debugging to Arduino, with simple software debugger
// Author: Joao Lopes
//
// Example to show how to use it.
//
// Example of use:
//
//   print macros:
//
//		printA(F("This is a always - var "));
//		printlnA(var);
//		printV(F("This is a verbose - var "));
//		printlnV(var);
//		printD(F("This is a debug - var "));
//		printlnD(var);
//		printI(F("This is a information - var "));
//		printlnI(var);
//		printW(F("This is a warning - var "));
//		printlnW(var);
//		printE(F("This is a error - var "));
//		printlnE(var);
//
//		printlnV("This not have args");
//
// 	debug macros (printf formatting):
//
//		debugA("This is a always - var %d", var);
//
//		debugV("This is a verbose - var %d", var);
//		debugD("This is a debug - var %d", var);
//		debugI("This is a information - var %d", var);
//		debugW("This is a warning - var %d", var);
//		debugE("This is a error - var %d", var);
//
//		debugV("This not have args");
//
///////

///////
// Note: this version is for Espressif or ARM boards,
//       Not using F() to reduce memory,
//       due these boards have memory a lot,
//	     and RAM memory is much faster than Flash memory
//       If want or need, please open the example in Directory Avr.
///////

////// Includes

#include "Arduino.h"

// SerialDebug Library

// Disable all debug ? Good to release builds (production)
// as nothing of SerialDebug is compiled, zero overhead :-)
// For it just uncomment the DEBUG_DISABLED
//#define DEBUG_DISABLED true

// Disable SerialDebug debugger ? No more commands and features as functions and globals
// Uncomment this to disable it 
//#define DEBUG_DISABLE_DEBUGGER true

// Debug TAG ?
// Usefull with debug any modules
// For it, each module must have a TAG variable:
// 		const char* TAG = "...";
// Uncomment this to enable it
//#define DEBUG_USE_TAG true

// Define the initial debug level here (uncomment to do it)
// #define DEBUG_INITIAL_LEVEL DEBUG_LEVEL_VERBOSE

// Force debug messages to can use flash ) ?
// Disable native Serial.printf (if have)
// Good for low memory, due use flash, but more slow and not use macros
//#define DEBUG_USE_FLASH_F true

// Include SerialDebug

#include "SerialDebug.h" //https://github.com/JoaoLopesF/SerialDebug

#ifdef BOARD_LOW_MEMORY
	#error "This is not for low memoy boards, please use the basic example"
	// If this error occurs, your board is a low memory board,
	// and for this, the default is mininum mode,
	// to especially to reduce program memory (flash)
	// You can do it:
	// - Open the basic example, or
    // - Open Advanced/Avr example (this uses F() to reduce RAM usage),
    //   and before, comment the DEBUG_MININUM in SerialDebug.h - line 64
#endif

////// Variables

// Time

uint8_t mRunSeconds = 0;
uint8_t mRunMinutes = 0;
uint8_t mRunHours = 0;

// Buildin Led ON ?

#ifndef LED_BUILTIN // For compatibility
	#ifdef BUILTIN_LED
		#define LED_BUILTIN BUILTIN_LED
	#else
		#define LED_BUILTIN 2
	#endif
#endif

boolean mLedON = false;

// Globals for this example

boolean mBoolean = false;
char mChar = 'X';
byte mByte = 'Y';
int mInt = 1;
unsigned int mUInt = 2;
long mLong = 3;
unsigned long mULong = 4;
float mFloat = 5.0f;
double mDouble = 6.0;

String mString = "This is a string";
String mStringLarge = "This is a large stringggggggggggggggggggggggggggggggggggggggggggggg";

char mCharArray[] = "This is a char array";
char mCharArrayLarge[] = "This is a large char arrayyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy";

int mIntArray[5] = {1 ,2 ,3, 4, 5};

//const char mCharArrayConst[] = "This is const";

////// Setup

void setup() {

    // Initialize the Serial

    Serial.begin(250000); // Can change it to 115200, if you want use debugIsr* macros

    delay(500); // Wait a time

  	// Debug

	// Attention:
    // SerialDebug starts disabled and it only is enabled if have data avaliable in Serial
    // Good to reduce overheads.
	// if You want debug, just press any key and enter in monitor serial

    // Note: all debug in setup must be debugA (always), due it is disabled now.

    Serial.println(); // To not stay in end of dirty chars in boot

    debugA("**** Setup: initializing ...");

    // Buildin led

    pinMode(LED_BUILTIN, OUTPUT);
    digitalWrite(LED_BUILTIN, LOW);

    // WiFi connection, etc ....

    // ...

#ifndef DEBUG_DISABLE_DEBUGGER

    // Add Functions and global variables to SerialDebug

    // Notes: descriptions is optionals

    // Add functions that can called from SerialDebug

    if (debugAddFunctionVoid("benchInt", &benchInt) >= 0) {
    	debugSetLastFunctionDescription("To run a benchmark of integers");
    }
    if (debugAddFunctionVoid("benchFloat", &benchFloat) >= 0) {
    	debugSetLastFunctionDescription("To run a benchmark of float");
    }
    if (debugAddFunctionVoid("benchGpio", &benchGpio) >= 0) {
    	debugSetLastFunctionDescription("To run a benchmark of Gpio operations");
    }
    if (debugAddFunctionVoid("benchAll", &benchAll) >= 0) {
    	debugSetLastFunctionDescription("To run all benchmarks");
    }

    if (debugAddFunctionVoid("benchSerialPrints", &benchSerialPrint) >= 0) {
    	debugSetLastFunctionDescription("To benchmarks standard Serial debug");
    }
    if (debugAddFunctionVoid("benchSerialDebug", &benchSerialDebug) >= 0) {
    	debugSetLastFunctionDescription("To benchmarks SerialDebug");
    }
    if (debugAddFunctionVoid("benchSerialDbgPr", &benchSerialDbgPr) >= 0) {
    	debugSetLastFunctionDescription("To benchmarks SerialDebug print macros");
    }
    if (debugAddFunctionVoid("benchSerialAll", &benchSerialAll) >= 0) {
    	debugSetLastFunctionDescription("To benchmarks all Serial");
    }

    if (debugAddFunctionStr("funcArgStr", &funcArgStr) >= 0) {
    	debugSetLastFunctionDescription("To run with String arg");
    }
    if (debugAddFunctionChar("funcArgChar", &funcArgChar) >= 0) {
    	debugSetLastFunctionDescription("To run with Character arg");
    }
    if (debugAddFunctionInt("funcArgInt", &funcArgInt) >= 0) {
    	debugSetLastFunctionDescription("To run with Integer arg");
    }

    // Add global variables that can showed/changed from SerialDebug
    // Note: Only global, if pass local for SerialDebug, can be dangerous

    if (debugAddGlobalUInt8_t("mRunSeconds", &mRunSeconds) >= 0) {
    	debugSetLastGlobalDescription("Seconds of run time");
    }
    if (debugAddGlobalUInt8_t("mRunMinutes", &mRunMinutes) >= 0) {
    	debugSetLastGlobalDescription("Minutes of run time");
    }
    if (debugAddGlobalUInt8_t("mRunHours", &mRunHours) >= 0) {
    	debugSetLastGlobalDescription("Hours of run time");
    }

    // Note: easy way, no descriptions ....

    debugAddGlobalBoolean("mBoolean", 	&mBoolean);
    debugAddGlobalChar("mChar", 		&mChar);
    debugAddGlobalByte("mByte", 		&mByte);
    debugAddGlobalInt("mInt", 			&mInt);
    debugAddGlobalUInt("mUInt", 		&mUInt);
    debugAddGlobalLong("mLong", 		&mLong);
    debugAddGlobalULong("mULong", 		&mULong);
    debugAddGlobalFloat("mFloat", 		&mFloat);
    debugAddGlobalDouble("mDouble", 	&mDouble);

    debugAddGlobalString("mString", 	&mString);

    // Note: For char arrays, not use the '&'

    debugAddGlobalCharArray("mCharArray", mCharArray);

    // Note, here inform to show only 20 characteres of this string or char array

    debugAddGlobalString("mStringLarge", &mStringLarge, 20);

    debugAddGlobalCharArray("mCharArrayLarge",
    									mCharArrayLarge, 20);

    // For arrays, need add for each item (not use loop for it, due the name can not by a variable)
    // Notes: Is good added arrays in last order, to help see another variables
    //        In next versions, we can have a helper to do it in one command

	debugAddGlobalInt("mIntArray[0]", 	&mIntArray[0]);
	debugAddGlobalInt("mIntArray[1]", 	&mIntArray[1]);
	debugAddGlobalInt("mIntArray[2]", 	&mIntArray[2]);
	debugAddGlobalInt("mIntArray[3]",	&mIntArray[3]);
	debugAddGlobalInt("mIntArray[4]",	&mIntArray[4]);

    // Add watches for some global variables
    // Note: watches can be added/changed in serial monitor too

	// Watch -> mBoolean when changed (put 0 on value)

	debugAddWatchBoolean("mBoolean", DEBUG_WATCH_CHANGED, 0);

	// Watch -> mRunSeconds == 10

	debugAddWatchUInt8_t("mRunSeconds", DEBUG_WATCH_EQUAL, 10);

	// Watch -> mRunMinutes > 3

	debugAddWatchUInt8_t("mRunMinutes", DEBUG_WATCH_GREAT, 3);

	// Watch -> mRunMinutes == mRunSeconds (just for test)

	debugAddWatchCross("mRunMinutes", DEBUG_WATCH_EQUAL, "mRunSeconds");

#endif // DEBUG_DISABLE_DEBUGGER

    // End

    debugA("**** Setup: initialized.");

}

////// Loop

void loop()
{
	// SerialDebug handle
	// NOTE: if in inactive mode (until receive anything from serial),
	// it show only messages of always or errors level type
	// And the overhead during inactive mode is very much low

	debugHandle();

	// Blink the led

	mLedON = !mLedON;
	digitalWrite(LED_BUILTIN, (mLedON)?LOW:HIGH);

	// Debug the time (verbose level)

	debugV("* Run time: %02u:%02u:%02u (VERBOSE)", mRunHours, mRunMinutes, mRunSeconds);

	if (mRunSeconds % 5 == 0) { // Each 5 seconds

		// Debug levels

		debugV("* This is a message of debug level VERBOSE");
		debugD("* This is a message of debug level DEBUG");
		debugI("* This is a message of debug level INFO");
		debugW("* This is a message of debug level WARNING");

		if (mRunSeconds == 55) { // Just for not show initially
			debugE("* This is a message of debug level ERROR");
		}

		mBoolean = (mRunSeconds == 30); // Just to trigger the watch

		// Functions example to show auto function name feature

		foo();

		bar();

		// Example of float formatting:

		mFloat += 0.01f;

#ifndef ARDUINO_ARCH_AVR // Native float printf support
		debugV("mFloat = %.3f", mFloat);
#else // For AVR, it is not supported, using String instead
		debugV("mFloat = %s", String(mFloat).c_str());
#endif

	}

	// Count run time (just a test - for real suggest the TimeLib and NTP, if board have WiFi)

	mRunSeconds++;

	if (mRunSeconds == 60) {
		mRunMinutes++;
		mRunSeconds = 0;
	}
	if (mRunMinutes == 60) {
		mRunHours++;
		mRunMinutes = 0;
	}
	if (mRunHours == 24) {
		mRunHours = 0;
	}

	// Delay of 1 second

	delay(1000);
}


// Functions example to show auto function name feature

void foo() {

  uint8_t var = 1;

  debugV("This is a debug - var %u", var);
}

void bar() {

  uint8_t var = 2;

  debugD("This is a debug - var %u", var);
}

////// Benchmarks - simple

// Note: how it as called by SerialDebug, must be return type void and no args
// Note: Flash F variables is not used during the tests, due it is slow to use in loops

#define BENCHMARK_EXECS 10000

// Simple benckmark of integers

void benchInt() {

	int test = 0;

	for (int i = 0; i < BENCHMARK_EXECS; i++) {

		// Some integer operations

		test++;
		test += 2;
		test -= 2;
		test *= 2;
		test /= 2;
	}

	// Note: Debug always is used here

	debugA("*** Benchmark of integers. %u exec.", BENCHMARK_EXECS);

}

// Simple benckmark of floats

void benchFloat() {

	float test = 0;

	for (int i = 0; i < BENCHMARK_EXECS; i++) {

		// Some float operations

		test++;
		test += 2;
		test -= 2;
		test *= 2;
		test /= 2;
	}

	// Note: Debug always is used here

	debugA("*** Benchmark of floats, %u exec.", BENCHMARK_EXECS);

}

// Simple benckmark of GPIO

void benchGpio() {

//	const int execs = (BENCHMARK_EXECS / 10); // Reduce it
	const int execs = BENCHMARK_EXECS;

	for (int i = 0; i < execs; i++) {

		// Some GPIO operations

		digitalWrite(LED_BUILTIN, HIGH);
		digitalRead(LED_BUILTIN);
		digitalWrite(LED_BUILTIN, LOW);

		analogRead(A0);
		analogRead(A0);
		analogRead(A0);

	}

	// Note: Debug always is used here

	debugA("*** Benchmark of GPIO. %u exec.", execs);

}

// Run all benchmarks

void benchAll() {

	benchInt();
	benchFloat();
	benchGpio();

	// Note: Debug always is used here

	debugA("*** All Benchmark done.");

}

// Serial benchmarks, to compare Serial.prints with SerialDebug

#define BENCHMARK_SERIAL 25

void benchSerialPrint() {

	// Note: Serial.printf is not used, due most Arduino not have this
	// Show same info to compare real speed
	// Same data size of SerialDebug to compare speeds of processing and not the time elapsed to send it

	unsigned long timeBegin = micros();

	for (uint16_t i = 0; i < BENCHMARK_SERIAL; i++) {

		Serial.print("(A ");
		Serial.print(millis());
		Serial.print(" benchSerialPrint");
#ifdef ESP32
		Serial.print(" C");
		Serial.print(xPortGetCoreID());
#endif
		Serial.print(") Exec.: ");
		Serial.print(i+1);
		Serial.print(" of ");
		Serial.println(BENCHMARK_SERIAL);

	}

	unsigned long elapsed = (micros() - timeBegin);

	Serial.print("*** Benchmark of Serial prints. Execs.: ");
	Serial.print(BENCHMARK_SERIAL);
	Serial.print(" time elapsed -> ");
	Serial.print(elapsed);
	Serial.println(" us");

}

void benchSerialDebug() {

	// Notes: printf formats can be used,
	// even if Arduino not have this, this is done in internal debugPrintf
	// Debug always level is used here

	debugShowProfiler(false, 0, false); // Disable the profiler during the test (the Serial.print not have it)

	unsigned long timeBegin = micros();

	for (uint16_t i = 0; i < BENCHMARK_SERIAL; i++) {

		debugA("Exec.: %u of %u", (i+1), BENCHMARK_SERIAL);

	}

	unsigned long elapsed = (micros() - timeBegin);

	// Note not using SerialDebug macros below, to show equals that SerialPrints

	Serial.print("*** Benchmark of Serial debugA. Execs.: ");
	Serial.print(BENCHMARK_SERIAL);
	Serial.print(" time elapsed -> ");
	Serial.print(elapsed);
	Serial.println(" us");

	debugShowProfiler(true, 0, false); // Reenable

}

void benchSerialDbgPr() {

	// Using print macros to avoid printf
	// Same data size of SerialDebug to compare speeds of processing and not the time elapsed to send it

	debugSetProfiler(false); // Disable it, due standard prints not have it

	unsigned long timeBegin = micros();

	for (uint16_t i = 0; i < BENCHMARK_SERIAL; i++) {

		printA("Exec.: ");
		printA(i+1);
		printA(" of ");
		printlnA(BENCHMARK_SERIAL);

	}

	unsigned long elapsed = (micros() - timeBegin);

	debugSetProfiler(true); // Restore

	// Note not using SerialDebug macros below, to show equals that SerialPrints

	Serial.print("*** Benchmark of Serial printA. Execs.: ");
	Serial.print(BENCHMARK_SERIAL);
	Serial.print(" time elapsed -> ");
	Serial.print(elapsed);
	Serial.println(" us");

}

void benchSerialAll() {

	benchSerialPrint();

	delay(1000); // To give time to send any buffered

	benchSerialDebug();

	delay(1000); // To give time to send any buffered

	benchSerialDbgPr();
}

// Example functions with argument (only 1) to call from serial monitor
// Note others types is not yet available in this version of SerialDebug

void funcArgStr (String str) {

	debugA("*** called with arg.: %s", str.c_str());
}
void funcArgChar (char character) {

	debugA("*** called with arg.: %c", character);
}
void funcArgInt (int number) {

	debugA("*** called with arg.: %d", number);
}

/////////// End

View raw code

Setup Codes for the Debugger

To call functions via Serial Monitor, or SerialDebugApp (see it in Part 3), you have to set the debugger in the setup() function of your sketch. For example:

// Add functions that can be called from SerialDebug

if (debugAddFunctionVoid("benchInt", &benchInt) >= 0) {
  debugSetLastFunctionDescription("To run a benchmark of integers");
}

if (debugAddFunctionVoid("benchFloat", &benchFloat) >= 0) {
  debugSetLastFunctionDescription("To run a benchmark of float");
}

if (debugAddFunctionVoid("benchGpio", &benchGpio) >= 0) {
  debugSetLastFunctionDescription("To run a benchmark of Gpio operations");
}

if (debugAddFunctionVoid("benchAll", &benchAll) >= 0) {
  debugSetLastFunctionDescription("To run all benchmarks");
}

if (debugAddFunctionVoid("benchSerialPrints", &benchSerialPrint) >= 0) {
  debugSetLastFunctionDescription("To benchmarks standard Serial debug");
}

if (debugAddFunctionVoid("benchSerialDebug", &benchSerialDebug) >= 0) {
  debugSetLastFunctionDescription("To benchmarks SerialDebug");
}
if (debugAddFunctionVoid("benchSerialDbgPr", &benchSerialDbgPr) >= 0) {
debugSetLastFunctionDescription("To benchmarks SerialDebug print macros");
}

if (debugAddFunctionVoid("benchSerialAll", &benchSerialAll) >= 0) {
  debugSetLastFunctionDescription("To benchmarks all Serial");
}

if (debugAddFunctionStr("funcArgStr", &funcArgStr) >= 0) {
  debugSetLastFunctionDescription("To run with String arg");
}

if (debugAddFunctionChar("funcArgChar", &funcArgChar) >= 0) {
  debugSetLastFunctionDescription("To run with Character arg");
}

if (debugAddFunctionInt("funcArgInt", &funcArgInt) >= 0) {
  debugSetLastFunctionDescription("To run with Integer arg");
}

You can set it in a shorter way with no descriptions:

debugAddFunctionVoid("benchInt", &benchInt);

Note: in the current version, it only supports functions with the following requirements:

Without any argument (void)
Or one argument of type int, char or String

Tip: you can create a generic function with one argument for debugging purpose. Then, you can call that function and pass different arguments to test it.

The previous code sets functions that can be called with an “f” command:

Note 1: command “f” without arguments lists all available functions.

Note 2: for this post, we use the ESP32 with the full features of SerialDebug, because it has enough memory.

To call the first function, just type the command: f 1

To call a function that requires an argument, you can write a command as follows “f 11 123“. In this case, the function 11 has received the value 123 as argument.

Show/Change Global Variables Values

To use global variables in the debugger, you need to set them in the setup() function:

// Add global variables that can showed/changed from SerialDebug
// Note: Only global, if pass local for SerialDebug, can be dangerous

if (debugAddGlobalUInt8_t("mRunSeconds", &mRunSeconds) >= 0) {
  debugSetLastGlobalDescription("Seconds of run time");
}
if (debugAddGlobalUInt8_t("mRunMinutes", &mRunMinutes) >= 0) {
  debugSetLastGlobalDescription("Minutes of run time");
}
if (debugAddGlobalUInt8_t("mRunHours", &mRunHours) >= 0) {
  debugSetLastGlobalDescription("Hours of run time");
}

// Note: easy way, no descriptions ....

debugAddGlobalBoolean("mBoolean", &mBoolean);
debugAddGlobalChar("mChar", &mChar);
debugAddGlobalByte("mByte", &mByte);
debugAddGlobalInt("mInt", &mInt);
debugAddGlobalUInt("mUInt", &mUInt);
debugAddGlobalLong("mLong", &mLong);
debugAddGlobalULong("mULong", &mULong);
debugAddGlobalFloat("mFloat", &mFloat);
debugAddGlobalDouble("mDouble", &mDouble);

debugAddGlobalString("mString", &mString);

// Note: For char arrays, not use the '&'

debugAddGlobalCharArray("mCharArray", mCharArray);

// Note, here inform to show only 20 characteres of this string or char array

debugAddGlobalString("mStringLarge", &mStringLarge, 20);

debugAddGlobalCharArray("mCharArrayLarge", mCharArrayLarge, 20);

Here’s some things you need to keep in mind when using the debugger show/change global variables values functionality:

It only works with global variables, defined out of any function, generally before all function definitions.
Don’t use this for local variables, because this will always be accessed, and if it is a local variable, it may not exist anymore, which would lead to invalid memory access.
You should have a function for each type of value, for example: debugAddGlobalString()
To help you migrating your code to use SerialDebug, there is a converter that reads your code and generates the setup() code for global variables automatically: SerialDebugConverter

List Global Variables

To list all global variables: just use command “g“. First, type “dbg” to activate the debugger and then use the “g” command .

Note: to avoid overheads of processing of debugger, it starts always disabled. If enabled, the debugger processes watches, as you can see in the following figure:

By default, the debugger will stop for watches. If you don’t want this to happen, use the command “wa ns“:

Now, use the command “g” to list all global variables:

To change any global variable, e.g. the global number 07 – mInt(int), just type the command “g 7 = 10“:

Note: the debugger will ask a confirmation to change the value of the variable. You just need to append “y” in command: “g 7 = 10 y”

You can use command “g ?“, to show help of commands for global variables.

Add/Change Watches for Global Variables

A watch is a good feature of any debugger. It observes a certain variable and shows a message if the variable has changed, or reached a pre-established condition. For example, imagine the following scenario:

We have a global variable mControl, that can’t be set to zero.
However, during the tests, it has received the value of zero.
To help detect this bug, we just add a watch with condition “mControl == 0“.
When it occurs, a watch is triggered, and we can see it in the Serial Monitor.
Analyzing the debug outputs before the watch allows us to determine the possible source of this bug.

Watches can be set in 2 ways:

In the setup() function (this watch isn’t lost if the device turns off or resets)
In the Serial Monitor or SerialDebugApp

Setting watches in setup() function

For the example SerialDebug_Advanced, we have the following:

// Watch -> mBoolean when changed (put 0 on value)
debugAddWatchBoolean("mBoolean", DEBUG_WATCH_CHANGED, 0);

// Watch -> mRunSeconds == 10
debugAddWatchInt("mRunSeconds", DEBUG_WATCH_EQUAL, 10);

// Watch -> mRunMinutes > 3// Watch -> mRunMinutes > 3
debugAddWatchUInt8_t("mRunMinutes", DEBUG_WATCH_GREAT, 3);

// Watch -> mRunMinutes == mRunSeconds (just for test)
debugAddWatchCross("mRunMinutes", DEBUG_WATCH_EQUAL, F("mRunSeconds"));

Note that the watch can be set for a specific condition or for when (global) variable is changed.

Here’s the types of watches that can be used:

DEBUG_WATCH_CHANGED -> Changed value ?
DEBUG_WATCH_EQUAL -> Equal (==)
DEBUG_WATCH_DIFF -> Different (!=)
DEBUG_WATCH_LESS -> Less (<=)
DEBUG_WATCH_GREAT -> Greater (>)
DEBUG_WATCH_LESS_EQ -> Less or equal (<=)
DEBUG_WATCH_GREAT_EQ -> Greater or equal (>=)

To list running watches, use “wa“:

To show help for watch commands, use “wa ?” command:

Debug Macros

In Part 1, we’ve seen the print macros for SerialDebug library. It is like a standard Serial.print(). We can also use the debug macros with the powerful printf formatting, regardless of whether the board has Serial.printf native or not. As far as I know, only Espressif boards have Serial.printf native.

For example, this snippet:

Serial.print("*** Example - varA = ");
Serial.print(varA);
Serial.print(" varB = ");
Serial.print(varB);
Serial.print(" varC = ");
Serial.print(varC);
Serial.println();

Can be converted to a single command:

debugD("*** Example - varA = %d varB = %d varC = %d", varA, varB, varC);

And you can add more format parameters:

debugD("*** Example - varA = %02d varB = %02d varC = %02d", varA, varB, varC);

The”%02″ means: minimum of 2 digits, lead of zero, if needed (e.g 2 is shown as 02).

Comparing the different types of debug outputs:

print macros is easier to migrate, and there isn’t overhead (it is a simple macro for Serial.print command)
debug macros is more powerful, but it isn’t so easy to migrate, and it has an extra overhead (about 1% more)

It’s up to you, you can either use the simple print macro or the powerful printf of debug macro.

Wrapping Up

In this second article you’ve learned how to use the Simple software debugger commands of the SerialDebug library in the Arduino IDE to list and run functions, list and change global variables and set watches.

In Part 3, you can discover how to take the most out of these features using the SerialDebugApp.

Continue Reading: Better Debugging for Arduino IDE: SerialDebugApp (Part 3)

Help me bring a better debug to the Arduino IDE using this library. Visit the GitHub page https://github.com/JoaoLopesF/SerialDebug, for more information, post issues and suggestions. Also, you can use the gitter chat room to share your feedback.

Thanks to Random Nerd Tutorials for the possibility of doing a post about SerialDebug library.

João Lopes

Random Nerd Tutorials has more than 200 free electronics projects and tutorials. Check them all in the next link: 200+ Electronics Projects and Tutorials

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3 thoughts on “Better Debugging for Arduino IDE using Software Debugger (Part 2)”

Dario

January 7, 2021 at 7:41 am

Hi! I’d like to understand how the watches work: the debugger needs to check if a global variable is changed and I guess that this means interrupting the flow of my original program to perform the comparison and the related actions. How is this done ? Is it done at compile time (in some way the code is modified and a routine is invoked whenever a watched variable is assigned a value) or is it done at runtime with a periodic interrupt that checks the values of the watched variables, or in some other way ?
Reply
Rene

January 11, 2021 at 12:33 pm

Unfortunately this project seems to be dead 🙁 The SeriaDebugApp is not downloadable from repo.
Reply
Ramey

November 29, 2022 at 11:48 pm

Could you include detailed instructions on installing the serialdebugconverter, I can’t get it installed.
Thanks
Ramey
Reply