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/*************************************************************************
* 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 7
#define MAX_CMD_LEN 6
const char PROGMEM s_initcmd[INIT_CMD_COUNT][MAX_CMD_LEN] = {"ATZ\r","ATE0\r","ATL1\r","ATI\r","0100\r","0120\r","0140\r"};
const char PROGMEM s_searching[] = "SEARCHING";
const char PROGMEM s_cmd_fmt[] = "%02X%02X 1\r";
const char PROGMEM s_cmd_sleep[MAX_CMD_LEN] = "atlp\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);
WriteData(cmd);
}
bool COBD::ReadSensor(byte pid, int& result, bool passive)
{
if (passive) {
bool hasData;
unsigned long tick = millis();
while (!(hasData = DataAvailable()) && millis() - tick < OBD_TIMEOUT_SHORT);
if (!hasData) {
errors++;
return false;
}
} else {
Query(pid);
}
return GetResponse(pid, result);
}
bool COBD::DataAvailable()
{
return OBDUART.available();
}
char COBD::ReadData()
{
return OBDUART.read();
}
void COBD::WriteData(const char* s)
{
OBDUART.write(s);
}
void COBD::WriteData(const char c)
{
OBDUART.write(c);
}
char* COBD::GetResponse(byte pid, char* buffer)
{
unsigned long startTime = millis();
byte i = 0;
for (;;) {
if (DataAvailable()) {
char c = ReadData();
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;
}
}
}
buffer[i] = 0;
char *p = buffer;
while ((p = strstr_P(p, s_response_begin))) {
p += 3;
if (pid == 0 || hex2uint8(p) == pid) {
errors = 0;
p += 2;
if (*p == ' ')
return p + 1;
}
}
return 0;
}
bool COBD::GetParsedData(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_SPEED:
case PID_BAROMETRIC:
case PID_INTAKE_PRESSURE:
result = GetSmallValue(data);
break;
case PID_TIMING_ADVANCE:
result = (GetSmallValue(data) - 128) >> 1;
break;
case PID_DISTANCE:
case PID_RUNTIME:
result = GetLargeValue(data);
break;
default:
return false;
}
return true;
}
bool COBD::GetResponse(byte pid, int& result)
{
char buffer[OBD_RECV_BUF_SIZE];
char* data = GetResponse(pid, buffer);
if (!data) {
// try recover next time
WriteData('\r');
return false;
}
return GetParsedData(pid, data, result);
}
bool COBD::GetResponsePassive(byte& pid, int& result)
{
char buffer[OBD_RECV_BUF_SIZE];
char* data = GetResponse(0, buffer);
if (!data) {
// try recover next time
return false;
}
pid = hex2uint8(data - 3);
return GetParsedData(pid, data, result);
}
void COBD::Sleep(int seconds)
{
char cmd[MAX_CMD_LEN];
strcpy_P(cmd, s_cmd_sleep);
WriteData(cmd);
if (seconds) {
delay((unsigned long)seconds << 10);
WriteData('\r');
}
}
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]);
WriteData(cmd);
}
n = 0;
prompted = 0;
currentMillis = millis();
for (;;) {
if (DataAvailable()) {
char c = ReadData();
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;
}
}
}
}
errors = 0;
return true;
}
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