BaseProtocol.cpp

/*
 * Copyright (C) 2017 3devo (http://www.3devo.eu)
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <stdint.h>
#include "Bus.h"
#include "Crc.h"
#include "BaseProtocol.h"

uint8_t configuredAddress = INITIAL_ADDRESS;

cmd_result handleCommand(uint8_t cmd, uint8_t *datain, uint8_t len, uint8_t *dataout, uint8_t maxLen) {
	if (maxLen < 5)
		return cmd_result(Status::NO_REPLY);

	switch (cmd) {
		case ProtocolCommands::GET_PROTOCOL_VERSION:
			dataout[0] = PROTOCOL_VERSION >> 8;
			dataout[1] = PROTOCOL_VERSION & 0xFF;
			return cmd_ok(2);

		case ProtocolCommands::SET_ADDRESS:
			if (len != 2)
				return cmd_result(Status::INVALID_ARGUMENTS);

			// Only respond if the hw type in the request is
			// the wildcard or matches ours.
			if (datain[1] != 0 && datain[1] != INFO_HW_TYPE)
				return cmd_result(Status::NO_REPLY);

			configuredAddress = datain[0];
			return cmd_result(Status::NO_REPLY);
		case ProtocolCommands::GET_MAX_PACKET_LENGTH:
			dataout[0] = MAX_PACKET_LENGTH >> 8;
			dataout[1] = MAX_PACKET_LENGTH & 0xFF;
			return cmd_ok(2);
		default:
			return processCommand(cmd, datain, len, dataout, maxLen);
	}
}


int BusCallback(uint8_t address, uint8_t *data, uint8_t len, uint8_t maxLen) {

	// Check that there is at least room for an address, status, length and CRC
	if (maxLen < 5)
		return 0;

	cmd_result res(0);
	// Check we received at least command and crc
	if (len < 3) {
		res = cmd_result(Status::INVALID_TRANSFER);
	} else {
		uint16_t crc = Crc16Ibm().update(address).update(data, len - 2).get();
		if (crc != (data[len - 2] | data[len - 1] << 8)) {
			// Invalid CRC, so no reply (we cannot
			// be sure that the message was really
			// for us, some someone else might also
			// reply).
			return 0;
		} else {
			// CRC checks out, process a command
			res = handleCommand(data[0], data + 1, len - 3, data + 3, maxLen - 5);
			if (res.status == Status::NO_REPLY)
				return 0;
		}
	}

	data[0] = address;
	data[1] = res.status;
	data[2] = res.len;
	len = res.len + 3;

	uint16_t crc = Crc16Ibm().update(data, len).get();
	data[len++] = crc;
	data[len++] = crc >> 8;

	return len;
}