ECEC 201 · Week 10

Modern Computer: Von Neumann

The demo is one C program: each button press logs one decoded register reading to a file.

Week 10 of 10 · Das Frite

ECEC 201 · Week 10 · In class

The demo is one C program: each button press logs one decoded register reading to a file.

It builds with make and runs clean under valgrind.
Write two questions a partner might ask about pointers or memory in your code, and your answers, before the demo.
That writing is the homework.

ECEC 201 · Week 10 · In class

Each partner answers one question about their own code.

Keep the repository as it was at the demo.

ECEC 201 · Week 10 · Lecture

One loop, three jobs

for (;;) {
	if (!wait_for_press(line_fd))       /* week 9 */
		break;
	int raw = read_reg(dev, addr, reg); /* week 8 */
	if (raw < 0)
		continue;                       /* log the failure? */
	log_reading(log_fd, raw);           /* week 7 */
}

Each job is a function you already tested on its own week.
main opens what the loop needs, runs the loop, and closes everything after it.

ECEC 201 · Week 10 · Lecture

Who owns what

Resource	Acquired by	Released by
Heap block	`malloc`	`free`, once
File descriptor	`open`	`close`
GPIO line	the line request	`close` on its descriptor

Write each release on the path out, including the error paths.

ECEC 201 · Week 10 · Lecture

Clean under valgrind

valgrind --leak-check=full ./prog must end with no blocks "definitely lost" and no invalid reads or writes.
--track-fds=yes also lists descriptors still open at exit.
Run it through a real session: press the button, let readings log, then stop the program the way the demo will.

ECEC 201 · Week 10 · Lecture

Freeze the demo

git clone into a new directory, then make there: that proves the repository builds without files only your board has.
git tag demo marks the commit you showed; later work does not move it.
The Makefile, the sources, and nothing generated: no .o files or binaries in git.

ECEC 201 · Week 10 · Lab

Lab

Demonstrate the project: each button press logs one decoded register reading to a file.
Each partner answers one question about pointers or memory in their own code. Second pass: run the demo under valgrind and show no leaks.
Assemble the lab hand-in: The demo, the repository with its `Makefile`, and the valgrind summary.

ECEC 201 · Week 10 · Lab

Hand in

The demo, the repository with its `Makefile`, and the valgrind summary.

ECEC 201 · Week 10 · Homework

Homework

Write two questions a partner might ask about pointers or memory in your code, and your answers, before the demo.

ECEC 201 · Week 10 · Homework

Turn in

The two questions and the two answers.

ECEC 201 · Week 10 · Read

Read

On the lab site: Module 12, A whole system, is a full product. This week grades one C program that joins a register and a button.