ELM327Processor.cpp

#include "ELM327Processor.h"

ELM327Processor::ELM327Processor() {
    obd2Handler = OBD2Handler::getInstance();
}

String ELM327Processor::processELMCmd(char *cmd) {
    String retString = String();
    String lineEnding;
    if (bLineFeed) lineEnding = String("\r\n");
    else lineEnding = String("\r");

    if (!strncmp(cmd, "at", 2)) {

        if (!strcmp(cmd, "atz")) { //reset hardware
            retString.concat(lineEnding);
            retString.concat("ELM327 v1.3a");
        }
        else if (!strncmp(cmd, "atsh",4)) { //set header address
            //ignore this - just say OK
            retString.concat("OK");
        }
        else if (!strncmp(cmd, "ate",3)) { //turn echo on/off
            //could support echo but I don't see the need, just ignore this
            retString.concat("OK");
        }
        else if (!strncmp(cmd, "ath",3)) { //turn headers on/off
            if (cmd[3] == '1') bHeader = true;
            else bHeader = false;
            retString.concat("OK");
        }
        else if (!strncmp(cmd, "atl",3)) { //turn linefeeds on/off
            if (cmd[3] == '1') bLineFeed = true;
            else bLineFeed = false;
            retString.concat("OK");
        }
        else if (!strcmp(cmd, "at@1")) { //send device description
            retString.concat("ELM327 Emulator");
        }
        else if (!strcmp(cmd, "ati")) { //send chip ID
            retString.concat("ELM327 v1.3a");
        }
        else if (!strncmp(cmd, "atat",4)) { //set adaptive timing
            //don't intend to support adaptive timing at all
            retString.concat("OK");
        }
        else if (!strncmp(cmd, "atsp",4)) { //set protocol
            //theoretically we can ignore this
            retString.concat("OK");
        }
        else if (!strcmp(cmd, "atdp")) { //show description of protocol
            retString.concat("can11/500");
        }
        else if (!strcmp(cmd, "atdpn")) { //show protocol number (same as passed to sp)
            retString.concat("6");
        }
        else if (!strcmp(cmd, "atd")) { //set to defaults
            retString.concat("OK");
        }
        else if (!strncmp(cmd, "atm", 3)) { //turn memory on/off
            retString.concat("OK");
        }
        else if (!strcmp(cmd, "atrv")) { //show 12v rail voltage
            //TODO: the system should actually have this value so it wouldn't hurt to
            //look it up and report the real value.
            retString.concat("14.2V");
        }
        else { //by default respond to anything not specifically handled by just saying OK and pretending.
            retString.concat("OK");
        }
    }
    else { //if no AT then assume it is a PID request. This takes the form of four bytes which form the alpha hex digit encoding for two bytes
        //there should be four or six characters here forming the ascii representation of the PID request. Easiest for now is to turn the ascii into
        //a 16 bit number and mask off to get the bytes
        if (strlen(cmd) == 4) {
            uint32_t valu = strtol((char *) cmd, NULL, 16); //the pid format is always in hex
            uint8_t pidnum = (uint8_t)(valu & 0xFF);
            uint8_t mode = (uint8_t)((valu >> 8) & 0xFF);
            Logger::debug(ELM327EMU, "Mode: %i, PID: %i", mode, pidnum);
            char out[7];
            char buff[10];
            if (obd2Handler->processRequest(mode, pidnum, NULL, out)) {
                if (bHeader) {
                    retString.concat("7E8");
                    out[0] += 2; //not sending only data bits but mode and pid too
                    for (int i = 0; i <= out[0]; i++) {
                        sprintf(buff, "%02X", out[i]);
                        retString.concat(buff);
                    }
                }
                else {
                    mode += 0x40;
                    sprintf(buff, "%02X", mode);
                    retString.concat(buff);
                    sprintf(buff, "%02X", pidnum);
                    retString.concat(buff);
                    for (int i = 1; i <= out[0]; i++) {
                        sprintf(buff, "%02X", out[i+2]);
                        retString.concat(buff);
                    }
                }
            }
        }
    }

    retString.concat(lineEnding);
    retString.concat(">"); //prompt to show we're ready to receive again

    return retString;
}