For others who have everything hooked up and are having issues reading data for desired OBD-II PIDs, here’s a script to help explore available data with SparkFun ODB-II UART and SparkFun MicroOLED Qwiic. It will show raw responses when there is data, and NODATA when there is not. This is good for those like me who can’t drag their desktop computer out to the car to read serial output nor have a budget for an OBD-II emulator.
#include <Wire.h> // Include Wire if you're using I2C
#include <SFE_MicroOLED.h> // Include the SparkFun MicroOLED library
// MicroOLED
//The library assumes a reset pin is necessary. The Qwiic OLED has RST hard-wired, so pick an arbitrarty IO pin that is not being used
#define PIN_RESET 9
//The DC_JUMPER is the I2C Address Select jumper. Set to 1 if the jumper is open (Default), or set to 0 if it's closed.
#define DC_JUMPER 1
MicroOLED oled(PIN_RESET, DC_JUMPER); // I2C declaration
char rxData[200];
char rxIndex = 0;
int counter = 0;
char pids[][5] = {
"0100", // Supported PIDs
"0120", // Supported PIDs
"0140", // Supported PIDs
"0160", // Supported PIDs
"0180", // Supported PIDs
"010C", // Engine RPM
"010D", // Vehicle speed
"010F", // Intake air temperature
"0111", // Throttle position
"011F", // Run time since engine start
"0121", // Distance traveled with malfunction indicator lamp (MIL) on
"012F", // Fuel Tank Level Input
"0130", // Warm-ups since codes cleared
"0131", // Distance traveled since codes cleared
"0133", // Absolute Barometric Pressure
"0143", // Absolute load value
"0145", // Relative throttle position
"0146", // Ambient air temperature
"014D", // Time run with MIL on
"014E", // Time since trouble codes cleared
"0153", // Absolute Evap system Vapor Pressure
"0159", // Fuel rail absolute pressure
"015C", // Engine oil temperature
"015E", // Engine fuel rate
"0161", // Driver's demand engine - percent torque
"0162", // Actual engine - percent torque
"0167", // Engine coolant temperature
"016B", // Exhaust gas recirculation temperature
"017F", // Engine run time
"019D", // Engine Fuel Rate
"019E", // Engine Exhaust Flow Rate
"019F", // Fuel System Percentage Use
"01A2", // Cylinder Fuel Rate
"01A6" // Odometer
};
char pidLabels[][40] = {
"Supported PIDs", // 0100
"Supported PIDs", // 0120
"Supported PIDs", // 0140
"Supported PIDs", // 0160
"Supported PIDs", // 0180
"Engine RPM", // 010C
"Vehicle speed", // 010D
"Intake air temperature", // 010F
"Throttle position", // 0111
"Run time since engine start", // 011F
"Distance traveled with MIL", // 0121
"Fuel Tank Level Input", // 012F
"Warm-ups since codes cleared", // 0130
"Distance traveled since codes cleared", // 0131
"Absolute Barometric Pressure", // 0133
"Absolute load value", // 0143
"Relative throttle position", // 0145
"Ambient air temperature", // 0146
"Time run with MIL on", // 014D
"Time since trouble codes cleared", // 014E
"Absolute Evap system Vapor Pressure", // 0153
"Fuel rail absolute pressure", // 0159
"Engine oil temperature", // 015C
"Engine fuel rate", // 015E
"Driver's demand engine - percent torque", // 0161
"Actual engine - percent torque", // 0162
"Engine coolant temperature", // 0167
"Exhaust gas recirculation temperature", // 016B
"Engine run time", // 017F
"Engine Fuel Rate", // 019D
"Engine Exhaust Flow Rate", // 019E
"Fuel System Percentage Use", // 019F
"Cylinder Fuel Rate", // 01A2
"Odometer" // 01A6
};
// get everything setup
void setup() {
Wire.begin();
// serial
Serial.begin(9600);
Serial.println("Debugging has begun.");
// oled
oled.begin(); // Initialize the OLED
oled.clear(ALL); // Clear the display's internal memory
oled.display(); // Display what's in the buffer (splashscreen)
delay(1000); // Delay 1000 ms
oled.clear(PAGE); // Clear the buffer.
// odb2
Serial1.begin(9600);
Serial1.flush();
//Reset the OBD-II-UART
delay(2000);
Serial1.println("ATZ");
delay(1000);
// don't echo sent commands when getting responses
Serial1.println("ATE0");
delay(1000);
}
// cycle through PIDs and show results on the OLED screen
void loop() {
// put your main code here, to run repeatedly:
Serial1.flush();
Serial1.println(pids[counter]);
delay(500);
getObd2Response();
displayMessage();
delay(7000);
counter += 1;
size_t n = sizeof(pids) / sizeof(pids[0]);
if (counter >= n) {
counter = 0;
}
}
// show a formatted message on the screen
void displayMessage(void) {
oled.clear(PAGE);
oled.setFontType(0);
oled.setCursor(0, 0);
String pidLabel((char*)pidLabels[counter]);
oled.print(pidLabel);
oled.setCursor(0, 24);
String message((char*)rxData);
oled.print(message);
oled.display();
}
// thanks: https://forum.sparkfun.com/viewtopic.php?t=35507
void getObd2Response(void)
{
char c;
if (Serial1.available() > 0) {
do {
c = Serial1.read();
// cut off the response if it is too big for some reason
if (rxIndex >= 199) {
c = '>';
}
if((c!= '>') && (c!='\r') && (c!='\n') && (c!=' ')) {
rxData[rxIndex++] = c; //Add whatever we receive to the buffer
}
} while(c != '>'); // The ELM327 ends its response with this char so when we get it we exit out.
rxData[rxIndex++] = '\0';// Converts the array into a string
rxIndex=0; // Set this to 0 so next time we call the read we get a "clean buffer"
} else {
// temp
rxData[rxIndex++] = 'N';
rxData[rxIndex++] = '\0'; // Converts the array into a string
rxIndex=0; // Set this to 0 so next time we call the read we get a "clean buffer"
}
}
Keep in mind that not all cars support all generic PIDs. Some PIDs may even be “new” such as the odometer reading PID listed at wikipedia with even less support. This script doesn’t have all PIDs included, so feel free to alter to taste.
