replay.h

A C header for recording and playing back VEX V5 robot movements using PROS

usage

1. Place replay.h in your include directory
2. Customize it. The beginning of the file defines what you're replaying.

   typedef struct {
   	double wheels[4]; // four wheels
   	
   	
   	int last; // indicate last step (important!!)
   } ReplayStep;

   values returned by motor_get_actual_velocity are doubles, but you can put anything in it. Make sure to leave int last, as it is used to indicate the last step in your sequence
3. use it!

Creating a replay

To create a replay sequence, first allocate it.

ReplayStep* replay = malloc(sizeof(ReplayStep) * REPLAY_LEN);
int step = 0;

This creates an array* of ReplaySteps called replay of length REPLAY_LEN, and an integer called step, which you'll likely want in order to keep track of the steps.

Now, when you want to record, simply set replay[step]'s members to whatever you like (such as motor speeds), and increment step before each delay call. When step has reached the desired length, set replay[step].last to 1. Here's a simple example that records the positions of four wheels

void opcontrol() {
	ReplayStep* replay = malloc(sizeof(ReplayStep) * REPLAY_LEN); // since you typically delay 2ms every step, 500 steps is typically equivalent to 1 second
	int step = 0;
	bool recording = false;
	/*
		insert controller-based movement and trigger for record here
	*/
	if (recording) {
		for (int i = 0; i < 4; i++) {
			replay[step].wheels[i] = motor_get_actual_velocity(wheels[i]);
		}
		step++;
		if (step == REPLAY_LEN) {
			replay[step - 1].last = 1; // indicate last step
			write_replay(replay, "/usd/replay"); // write the replay to the SD card
			step = 0;
			recording = false;
		}
	}
	delay(2); // make sure the delay is the same during both record and playback
}
	

Saving a replay

Just call write_replay(replay, filename). If you're using an SD card in your VEX brain, the filename should start with /usd/. If you've allocated more memory than the length of your replay, all you have to do is mark the last step you want as last, and when it is saved, everything after the first step where replay[i].last == 1 will be removed

Replaying a replay

First, load the replay.

ReplayStep* replay = read_replay(REPLAY_FILENAME);

Now, you can do whatever you want with it. The following example spins four wheels as they were recorded.

for (int i = 0; replay[i-1].last != 1; i++) {
	for (int j = 0; j < 4; j++) {
		motor_move_velocity(wheel_port[j], replay[i].wheels[j]);
	}
	delay(2);
}

*don't at me