8. Debugging a Microcontroller Program Part 2

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Из курса от партнера University of Colorado Boulder

Embedded Software and Hardware Architecture

оценки

University of Colorado Boulder

Embedded Software and Hardware Architecture

оценки

Embedded Software and Hardware Architecture is a first dive into understanding embedded architectures and writing software to manipulate this hardware. You will gain experience writing low-level firmware to directly interface hardware with highly efficient, readable and portable design practices. We will now transition from the Host Linux Machine where we built and ran code in a simulated environment to an Integrated Development Environment where you will build and install code directly on your ARM Cortex-M4 Microcontroller. Course assignments include writing firmware to interact and configure both the underlying ARM architecture and the MSP432 microcontroller platform. The course concludes with a project where you will develop a circular buffer data structure. In this course you will need the Texas Instruments LaunchPad with the MSP432 microcontroller in order to complete the assignments. Later courses of the Specialization will continue to use this hardware tool to develop even more exciting firmware.

Из урока

Manipulating Memory

Module 2 will introduce the learner to more advanced firmware techniques as well move us into some hands on firmware for the microcontroller. We start by building our own memory access methods that will allow a programmer to manipulate peripheral memory bit fields to configure microcontroller peripherals and core architecture concepts. This will include more complex use of pointers for register definition files and function pointers for interrupt vector tables The module concludes with an in-depth look into the features of on-target debugging on a microcontroller and a hands-on example.

1. Memory Access and Manipulation Introduction4:55

2. Bit Manipulation9:53

3. IO Port Configuration Example9:43

4. Creating Software Interfaces for Hardware10:11

5. Advanced Pointer Use6:24

6. Function Pointers6:38

7. Debugging a Microcontroller Program Part 17:48

8. Debugging a Microcontroller Program Part 28:18

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Alex Fosdick
Instructor
Electrical, Computer, and Energy Engineering

In this video, we will make a demo with the debugger.

When we last left off, we introduced many features of the debugger.

Now, we will go through a simple example, showing all of these different features.

In general,

the debug features we will discuss are not really unique to any one debugger.

They exist in nearly every debugger.

We'll be using Code Composer Studio Six for this, or CCS6 from Texas Instruments.

CCS is based on the Eclipse IDE.

And many of the micro controller IDEs out on the market do use Eclipse

as their base.

This means that most of the things you will see in this video,

including the application itself, will be identical or

look very similar to many other debugger applications.

Let's start by explaining the program we have written.

The program starts with a list of general includes of various header files,

including the register definition file, msp.h.

After the includes, we have some preprocessor defines used for

some constant expressions in the program.

Then we have a program declaration for a function, blink_led_forever().

This is a simple function that contains an infinite loop

while flipping a port pen on and off.

Next, there are two arrays defined in global memory.

These two arrays are both uint8 arrays, each 16 bytes long.

Jumping into the main, the first line of code disables the watchdog timer.

This prevents the processor from auto restarting when the watchdog expires.

We'll go over the watchdog in more detail later in the course.

Next, we configure port 1 pin 0 to an output direction.

We then initialize our two arrays.

Array1 is initialized to the values 0 through 15.

Array2 uses our memset function to initialize all members to hex ff.

I have added in two simple NOP commands

that we will map the break points before and after the memmove operation.

Finally, we call the blink_led_forever function, which just toggles on and

off the port pin P1.0.

We start compiling the project by clicking on the hammer build icon or

through the project menu.

Build output will be seen in the Console Output window on the bottom.

You should make sure all your bugs are fixed before you can even move on

to debugging.

Here, we have missed a semicolon, and

the console tells us that there is a missing semicolon on this line.

This output should be familiar from our compilation assignment, as it's the output

generated from an internally managed build system that uses make.

You will notice that there is also an indicator of a red x on the line,

with the error.

In this case the error comes from the previous line of code.

We will add the semicolon back in.

Now that all errors are fixed, we will click the debug icon.

And that looks like a little bug.

This will move our view in the IDE from the CCS edit view into the CCS debug view.

This operation will automatically rebuild your project, upload that project to our

board, and additionally pause our program at the entry point domain.

At this interpoint domain, none of our local variables have been initialized.

You can open up the expressions window and add in the array1,

the array2, and i variables.

When looking at data, you often need to format in the way you wish to view it.

Here, we will set it to appear as hex numbers.

The arrays have valid addresses, whereas the variable i does not.

The variable i has not been declared or initialized.

The variable i could also be seen in the variables tab.

If you switch over to the variables window, you can see the local variable i.

We will set a watch point on this variable i to break when it has been changed.

If you inspect the array values of the array elements in the expressions tab,

you will see that they have all been initialized to zero,

because they are declared in the BSS region.

Now, I'm going to switch to the break points view and send a break point

on the line of code where the P1.0 pin is configured to be an output.

I will press the play button, and let this code run until it hits that break point.

You can now open the register's view, and

we can look at the direction register before and after the configuration.

From the list, select the P1 options and see all the port 1 registers.

Now select P1 DUR.

Reading this value before making the assignment,

you can see that the register port pin 0 is set to a 0.

We can now click the Step Over button, which is the arrow icon.

And this will move our C program to the next line of C code.

Now, re-reading the direction register, we can see that bit 1 has been set.

You can actually manually change this value by clicking on the register and

setting it to any valid value you're interested in.

I will keep it set to the output direction.

Next, I will disable my breakpoints on the direction line.

I will now place a breakpoint on the memset function.

In the memory browser, I will point the browser

to the location of the array I want and format it to look like a list of uint8s.

You can see the current content of array1 before the for loop executes.

Both array1 and array 2 are all set to 0.

After clicking the go button,

the program will run to the first instance of the index i.

This pauses because we have a watch point on i being changed.

If we press continue again,

it will run through the loop until i has been changed a second time.

I will remove this watch point and press run.

Now, we will run through the full loop until we get to the memset function.

And as seen in our memory browser window,

the array run region has been initialized to the value 0 through 15.

We now click the step over button and

the array2 element has been initialized to hexFF value.

Now, let's set a new breakpoint at the second NOP function, and

let's remove our previous ones.

This then move operation is going to move eight bytes from array1 into array2.

Clicking Run, we will see that data has been moved properly from array1 to array2.

This feature of browsing memory will be important when we start

coding data structures in later modules.

Now, let's step through until we get to the blink_led_forever function.

In this case, we're going to use the step into button.

This will allow our program to move into a function instead of past it, and

view what is happening on the inside.

After doing so, we moved into this routine, and

we can see that the bug view has moved into that function.

Here we're using an XOR operator to simply toggle the BIT0 of port 1 to flip

the pin on and off, and

thus create our blinking program based on some arbitrary for loop iterator.

Now, if we just press play, the program will blink a number of times.

When you are satisfied with all the blinking, you can click the Stop button.

This concludes our debug demo.

There are many online resources and videos of many other Eclipse based IDEs and

Code Composer that you can watch to get some more help or

find other features that we did not discuss.

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