2.2.5 Target Debugging

In an integrated development environment (IDE), the execution of the code is tested on a debugger. The debugger can be a software program that simulates the operation of the microcontroller for testing, or it can be a hardware instrument to analyze the program as it executes in the application.

The IDE and Debugging

Debugging usually becomes urgent near the end of the project design cycle. As deadlines loom, getting the application to function as originally designed is the last step before going into deployment of the product and often has the most influence on producing delays in getting a product out. That’s where an integrated development environment is most important. Doing fine “tweaks” to the code, recompiling, downloading and testing all require time. Using all tools within a single environment will reduce the time around the “cycle.” These last steps, where critical bugs are worked out, are a test for the embedded systems designer. The right tool can save time. With MPLAB X IDE, many tools can be selected, but they all will have a similar interface and the learning curve from simulator to low-cost in-circuit debugger to powerful in-circuit emulator is small.

Software Debuggers

Simulators are built into MPLAB X IDE so a program can be tested without any additional hardware. A simulator is a software debugger, and the debugger functions for the simulator are almost identical to the hardware debuggers, allowing a new tool to be learned with ease. Usually a simulator runs somewhat slower than an actual microcontroller since the CPU in the computer is being used to simulate the operations of the microcontroller.

Hardware Debuggers

There are two types of hardware that can be used with MPLAB X IDE: programmers and hardware debuggers. A programmer simply burns the machine code from the PC into the internal memory of the target microcontroller. The microcontroller can then be plugged into the application and, hopefully, it will run as designed.

Usually, however, the code does not function exactly as anticipated, and the engineer is tasked with reviewing the code and its operation in the application to determine how to modify the original source code to make it execute as desired. This process is called debugging. As noted previously, the simulator can be used to test how the code will operate, but once a microcontroller is programmed with the firmware, many things outside the scope of the simulator come into play. Using just a programmer, the code could be changed, reprogrammed into the microcontroller and plugged into the target for retest, but this could be a long, laborious cycle if the code is complex, and it is difficult to understand exactly what is going wrong in the hardware.

This is where a hardware debugger is useful. Hardware debuggers can be in-circuit emulators or in-circuit debuggers, which use microcontrollers that have special built-in debugging features. A hardware debugger, like a simulator, allows the engineer to inspect variables at various points in the code, and single step to follow instructions as the hardware interacts with its specialized circuitry.