path: root/libraries/OBD/OBD.cpp

/*************************************************************************
* OBD-II (ELM327) data accessing library for Arduino
* Distributed under GPL v2.0
* Copyright (c) 2012 Stanley Huang <stanleyhuangyc@gmail.com>
* All rights reserved.
*************************************************************************/

#include <Arduino.h>
#include <avr/pgmspace.h>
#include "OBD.h"

#define INIT_CMD_COUNT 4
#define MAX_CMD_LEN 6

const char PROGMEM s_initcmd[INIT_CMD_COUNT][MAX_CMD_LEN] = {"ATZ\r","ATE0\r","ATL1\r","ATI\r"};
const char PROGMEM s_searching[] = "SEARCHING";
const char PROGMEM s_cmd_fmt[] = "%02X%02X 1\r";
const char PROGMEM s_cmd_sleep[] = "atlp\r";
const char PROGMEM s_cmd_vin[] = "0902\r";
const char PROGMEM s_response_begin[] = "41 ";

unsigned int hex2uint16(const char *p)
{
	char c = *p;
	unsigned int i = 0;
	for (char n = 0; c && n < 4; c = *(++p)) {
		if (c >= 'A' && c <= 'F') {
			c -= 7;
		} else if (c>='a' && c<='f') {
			c -= 39;
        } else if (c == ' ') {
            continue;
        } else if (c < '0' || c > '9') {
			break;
        }
		i = (i << 4) | (c & 0xF);
		n++;
	}
	return i;
}

unsigned char hex2uint8(const char *p)
{
	unsigned char c1 = *p;
	unsigned char c2 = *(p + 1);
	if (c1 >= 'A' && c1 <= 'F')
		c1 -= 7;
	else if (c1 >='a' && c1 <= 'f')
	    c1 -= 39;
	else if (c1 < '0' || c1 > '9')
		return 0;

	if (c2 >= 'A' && c2 <= 'F')
		c2 -= 7;
	else if (c2 >= 'a' && c2 <= 'f')
	    c2 -= 39;
	else if (c2 < '0' || c2 > '9')
		return 0;

	return c1 << 4 | (c2 & 0xf);
}

void COBD::Query(unsigned char pid)
{
	char cmd[8];
	sprintf_P(cmd, s_cmd_fmt, dataMode, pid);
	write(cmd);
}

bool COBD::ReadSensor(byte pid, int& result, bool passive)
{
	// send a query command
	Query(pid);
	// wait for reponse
	bool hasData;
	unsigned long tick = millis();
	do {
		DataIdleLoop();
	} while (!(hasData = available()) && millis() - tick < OBD_TIMEOUT_SHORT);
	if (!hasData) {
		errors++;
		return false;
	}
	// receive and parse the response
	return GetResponseParsed(pid, result);
}

bool COBD::available()
{
	return OBDUART.available();
}

char COBD::read()
{
	return OBDUART.read();
}

void COBD::write(const char* s)
{
	OBDUART.write(s);
}

void COBD::write(const char c)
{
	OBDUART.write(c);
}

int COBD::GetConvertedValue(byte pid, char* data)
{
	int result;
	switch (pid) {
	case PID_RPM:
		result = GetLargeValue(data) >> 2;
		break;
	case PID_FUEL_PRESSURE:
		result = GetSmallValue(data) * 3;
		break;
	case PID_COOLANT_TEMP:
	case PID_INTAKE_TEMP:
	case PID_AMBIENT_TEMP:
		result = GetTemperatureValue(data);
		break;
	case PID_ABS_ENGINE_LOAD:
		result = GetLargeValue(data) * 100 / 255;
		break;
	case PID_MAF_FLOW:
		result = GetLargeValue(data) / 100;
		break;
	case PID_THROTTLE:
	case PID_ENGINE_LOAD:
	case PID_FUEL_LEVEL:
		result = GetPercentageValue(data);
		break;
	case PID_TIMING_ADVANCE:
		result = (GetSmallValue(data) - 128) >> 1;
		break;
	case PID_DISTANCE:
	case PID_RUNTIME:
		result = GetLargeValue(data);
		break;
	default:
		result = GetSmallValue(data);
	}
	return result;
}

char* COBD::GetResponse(byte& pid, char* buffer)
{
	unsigned long startTime = millis();
	byte i = 0;

	for (;;) {
		if (available()) {
			char c = read();
			buffer[i] = c;
			if (++i == OBD_RECV_BUF_SIZE - 1) {
			    // buffer overflow
			    break;
			}
			if (c == '>' && i > 6) {
				// prompt char reached
				break;
			}
		} else {
			buffer[i] = 0;
			unsigned int timeout;
			if (dataMode != 1 || strstr_P(buffer, s_searching)) {
				timeout = OBD_TIMEOUT_LONG;
			} else {
				timeout = OBD_TIMEOUT_SHORT;
			}
			if (millis() - startTime > timeout) {
				// timeout
				errors++;
				break;
			}
			DataIdleLoop();
		}
	}
	buffer[i] = 0;

	char *p = buffer;
	while ((p = strstr_P(p, s_response_begin))) {
		p += 3;
		byte curpid = hex2uint8(p);
		if (pid == 0) pid = curpid;
		if (curpid == pid) {
			errors = 0;
			p += 2;
			if (*p == ' ')
			    return p + 1;
		}
	}
	return 0;
}

bool COBD::GetResponseParsed(byte& pid, int& result)
{
	char buffer[OBD_RECV_BUF_SIZE];
	char* data = GetResponse(pid, buffer);
	if (!data) {
		// try recover next time
		write('\r');
		return false;
	}
	result = GetConvertedValue(pid, data);
	return true;
}

void COBD::Sleep(int seconds)
{
	char cmd[MAX_CMD_LEN];
	strcpy_P(cmd, s_cmd_sleep);
	write(cmd);
	if (seconds) {
		delay((unsigned long)seconds << 10);
		write('\r');
	}
}

bool COBD::IsValidPID(byte pid)
{
	if (pid >= 0x7f)
		return false;
	pid--;
	byte i = pid >> 3;
	byte b = 0x80 >> (pid & 0x7);
	return pidmap[i] & b;
}

bool COBD::Init(bool passive)
{
	unsigned long currentMillis;
	unsigned char n;
	char prompted;
	char buffer[OBD_RECV_BUF_SIZE];

	for (unsigned char i = 0; i < INIT_CMD_COUNT; i++) {
		if (!passive) {
			char cmd[MAX_CMD_LEN];
			strcpy_P(cmd, s_initcmd[i]);
			write(cmd);
		}
		n = 0;
		prompted = 0;
		currentMillis = millis();
		for (;;) {
			if (available()) {
				char c = read();
				if (c == '>') {
				    buffer[n] = 0;
				    prompted++;
				} else if (n < OBD_RECV_BUF_SIZE - 1) {
				    buffer[n++] = c;
				}
			} else if (prompted) {
				break;
			} else {
				unsigned long elapsed = millis() - currentMillis;
				if (elapsed > OBD_TIMEOUT_INIT) {
					// init timeout
					//WriteData("\r");
					return false;
				}
				InitIdleLoop();
			}
		}
	}

	// load pid map
	memset(pidmap, 0, sizeof(pidmap));
	for (byte i = 0; i < 4; i++) {
	byte pid = i * 0x20;
	Query(pid);
	char* data = GetResponse(pid, buffer);
	if (!data) break;
	data--;
	for (byte n = 0; n < 4; n++) {
	    if (data[n * 3] != ' ')
	        break;
	    pidmap[i * 4 + n] = hex2uint8(data + n * 3 + 1);
	}
	}
	errors = 0;
	return true;
}