Fix #2

Control Interface.md

Control interface

This document defines the structure and parameters of messages sent between the Arduino microcontroller on either robot, and the Raspberry Pi on the secondary robot which handles high level logic and control

Message structure

struct Message {
	char command;
	int16_t payload;
}

Pi to Arduino

Name	Char	Parameter	Description
forward	F	distance	Moves the robot forward by the distance in mm. Fires collision/status message on completion/failure.
turn	T	angle	Fires status(0) message on completion
do	D	task	Starts an activity on the arduino (e.g. moving a servo). task is a number representing that activity.
align	A	distance	Moves backwards into the wall to align, then forwards by distance, similar to forward.
request	R	component	Reads a value from a component (e.g. servo rotation). component is a number representing that component.

Arduino to Pi

Name	Char	Parameter	Description
collision	c	distance	Fired during forward/align action by the arduino, sending distance travelled.
status	s	error	Returns an error code for some arbitrary action. If error is 0, no error was encountered (success).
return	r	data	Response to a request message.
log	l	length	Notifies the pi that the arduino is about to send a debug message. length is the length of the message.

debug.cpp

#include "debug.h"

namespace robot {
	namespace debug {
		void log(const char* message, const char* function) {
			size_t message_len = strlen(message);
			size_t function_len = strlen(function);
			Serial.write('l');
			Serial.write(message_len + function_len);
			Serial.write(message, message_len);
			Serial.write(function, function_len);
		}

		void error(const char* error_message, const char* function) {
			size_t message_len = strlen(error_message);
			size_t function_len = strlen(function);
			Serial.write('l');
			Serial.write(message_len + function_len + 5 + 2); // + 5 + 2 bytes for the "[ in " and "]\n" strings
			Serial.write(error_message, message_len);
			Serial.print("[ in "); // TODO: gotta check that this is actually writing 5 bytes, not 6 (including \0)
			Serial.write(function, function_len);
			Serial.print("]\n"); // TODO: gotta check that this is actually writing 2 bytes, not 3 (including \0)

			delay(100);
			exit(1);
		}

		bool assert(bool value, const char* error_message, const char* function) {
			if (!value) {
				robot::debug::error(error_message, function);
			}

			return value;
		}

		uint8_t assert(uint8_t value, const char* error_message, const char* function) {
			if (value == 0) {
				robot::debug::error(error_message, function);
			}

			return value;
		}
	}
}

debug.h

#pragma once

#include <arduino.h>

// use rerror(message) to error with a message
#define rerror(s) robot::debug::error(s, __FUNCTION__);

// use rassert(condition, message) to error with a message if `condition` is false
#define rassert(v, s) robot::debug::assert(v, s, __FUNCTION__);

// inline __attribute__((always_inline))

namespace robot {
	namespace debug {
		void log(const char* message, const char* function);

		void error(const char* error_message, const char* function);

		bool assert(bool value, const char* error_message, const char* function);
		uint8_t assert(uint8_t value, const char* error_message, const char* function);
	}
}