Custom microprocessor (Arduino, Pi, etc) Jeep project thread
- Thread starter freedom_in_4low
- Start date
I took the FE and the PE in mechanical back in the dark ages (1990), one year out of college, but I took a review class to prepare for both because I was told that you need a strategy to pass the exam, and the course did that - I found that very helpful. By the way, back then, the PE was 10 questions, but they were multi-part - like a college exam. You had to show your calculations, and that's how you were graded. Supposedly, they used professors to grade the exams.
That process was definitely easier than when I took the PE in civil 18 years later (in 2007). Since I never had any civil courses in college, I took a Testmasters in-person "review" class, but instead of treating it as a review class, I used it to put together a study schedule and studied for six months - basically teaching myself enough civil engineering to pass the exam. I thought Testmasters was such a good program that in my last job, I paid for a Testmasters course for all EITs sitting for the PE exam that worked for me (half up front, the other half paid upon passing). Over the years, the passing rate was very high for those employees - probably 95%, much higher than the average passing rate.
I can't recommend Testmasters(.com) enough for preparing for the PE exam, but most civil engineering students take the FE in their senior year, so I have no experience with their FE prep course. However, I'd bet it's worth the money. Their PE courses are expensive, time-consuming, but worth the investment. Perhaps you could get your employer to pay for the courses?
Good luck! As App posted, "You can do it!"
I'm using Kaplans PPI2pass for the FE, it seemed to have among the best reviews and had an on-demand (vs live video) option that I didn't consider overly expensive. I'll look into your recommendation once I pass the FE, thanks for that! I've already met the experience requirement so I'll roll right into PE registration and prep as soon as I have the FE result.
I may ask my employer to pay for the PE review but I won't for the FE because I should have done it in 2006.
I'm far behind the curve on this stuff, but I started catching up this week. I got an ESP32 (not the nano like you're using) and set off to make it talk to my bluetooth OBDII dongle (my primary unit is an OBDLink CX, which I really like) but apparently there are some BLE & security stuff that make it challenging to talk to the esp32. So then I got a chinesium ELM327 dongle, and I think it just sucked out loud because it wouldn't connect either. Then I replaced it with a slightly more expensive ($12) VEEPEAK unit and it connected right away.
Of course my office can't quite reach my garage to do bluetoothy things, and I didn't want to move my laptop (and give up my massive monitor setup), so I had it use a socketio to log the messages to a webpage viewable on my phone. That proved to be not a perfect solution, because the amount of code/test/code/test made not having the laptop in the garage impractical.
I mostly used chatGPT & Claude to generate the code...I barely speak C++ and I certainly don't know how to interface with a serial device. But after seeing it I mostly understand, and will be able to extrapolate. At any rate, it took a minute (read: much longer than a minute) to figure out that I needed to add some code to auto-negotiate the protocol, but as of last night I had my first success.
Longer term, I want to build a little sensor array that will allow me (or somebody else) to easily perform the 32RH pressure tests. The manual uses 2 pressure sensors that you have to repeatedly move around to conduct the test. You can get a transducer for like $10 on amazon, so I figure, why not just get enough to do the test in one pass? Then collect that data along with the RPM data needed for the test, graph/evaluate it against the test criteria, and Bob's your uncle.
Even longer term I'm thinking of streaming obdii data to something like Redpanda & Timeplus and then having a grafana dashboard on a display in my garage. Yeah, my phone app already does that, but this is a cool way to play with a bunch of tech. But that's down the road a bit.
Of course my office can't quite reach my garage to do bluetoothy things, and I didn't want to move my laptop (and give up my massive monitor setup), so I had it use a socketio to log the messages to a webpage viewable on my phone. That proved to be not a perfect solution, because the amount of code/test/code/test made not having the laptop in the garage impractical.
I mostly used chatGPT & Claude to generate the code...I barely speak C++ and I certainly don't know how to interface with a serial device. But after seeing it I mostly understand, and will be able to extrapolate. At any rate, it took a minute (read: much longer than a minute) to figure out that I needed to add some code to auto-negotiate the protocol, but as of last night I had my first success.
Longer term, I want to build a little sensor array that will allow me (or somebody else) to easily perform the 32RH pressure tests. The manual uses 2 pressure sensors that you have to repeatedly move around to conduct the test. You can get a transducer for like $10 on amazon, so I figure, why not just get enough to do the test in one pass? Then collect that data along with the RPM data needed for the test, graph/evaluate it against the test criteria, and Bob's your uncle.
Even longer term I'm thinking of streaming obdii data to something like Redpanda & Timeplus and then having a grafana dashboard on a display in my garage. Yeah, my phone app already does that, but this is a cool way to play with a bunch of tech. But that's down the road a bit.
Which VEEPEAK device did you get, the bright blue transparent case one?
https://www.amazon.com/Veepeak-Blue...DashCommand/dp/B011NSX27A/?tag=wranglerorg-20
I thought about getting a OBDLink CX because I like my OBDLink SX (USB cable). But from what I could find, they encrypt the Bluetooth stream, and use a non-published PIN. I'm not sure if a RasPi Pico W or an ESP32 or ESP8266 can deal with that. So I'm looking for a cheap way to experiment without wasting money on the many chinesium devices which just don't work well.
https://www.amazon.com/Veepeak-Blue...DashCommand/dp/B011NSX27A/?tag=wranglerorg-20
I thought about getting a OBDLink CX because I like my OBDLink SX (USB cable). But from what I could find, they encrypt the Bluetooth stream, and use a non-published PIN. I'm not sure if a RasPi Pico W or an ESP32 or ESP8266 can deal with that. So I'm looking for a cheap way to experiment without wasting money on the many chinesium devices which just don't work well.
I'm using this exact one, which does have a blue transparent case: https://www.amazon.com/dp/B011NSX27A?tag=wranglerorg-20
How the OBDLinkCX connects is confusing to me, because (a) I don't believe I've ever used a pin to connect it, and I swear I've used it with multiple apps, so they can't all know the secret pin or have the certificate or whatever tricky thing it's using to connect. And it's possible I could've overcome it, but I didn't want the first step in this journey to be how to overcome bluetooth security so I spent $12 in the name of progress.
.
That said, for just ordinary monitoring, code reading, etc, I am extremely happy with the OBDLink CX and the OBDLink app (and now I'm wondering if I have in fact used the dongle with other apps). But this thread is all about doing things the hard way.
How the OBDLinkCX connects is confusing to me, because (a) I don't believe I've ever used a pin to connect it, and I swear I've used it with multiple apps, so they can't all know the secret pin or have the certificate or whatever tricky thing it's using to connect. And it's possible I could've overcome it, but I didn't want the first step in this journey to be how to overcome bluetooth security so I spent $12 in the name of progress.
. That said, for just ordinary monitoring, code reading, etc, I am extremely happy with the OBDLink CX and the OBDLink app (and now I'm wondering if I have in fact used the dongle with other apps). But this thread is all about doing things the hard way.
Would you mind sharing your code?
I have an ESP32 which will scan for Bluetooth devices, and finds the VEEPEAK dongle (gets its name and MAC address), and pairs with it. But so far I can't get any further response out of it. I know it will need to negotiate the protocol, and I might be able to work through that. But after it connects (pairs) it just doesn't respond at all. I suspect I'm missing some initial setup thing.
Let me get a working version again...I had it working, then started to make some changes and it stopped working. And OF COURSE I haven't put any of this into github so I can't even rollback to a clean commit. Negotiating the protocol was a key step to getting everything talking, though.
I didn't touch the initialize function, so it should still work. We lost internet at the house for the better part of 2 weeks and I'm not nearly good enough to know all these classes & APIs without a lot of Claude, so I've already forgotten a lot of what I had figured out. Use at your own risk.
I didn't touch the initialize function, so it should still work. We lost internet at the house for the better part of 2 weeks and I'm not nearly good enough to know all these classes & APIs without a lot of Claude, so I've already forgotten a lot of what I had figured out. Use at your own risk.
C++:
bool initializeOBD() {
Serial.println("Initializing OBD-II communication...");
// Clear buffer first
while (SerialBT.available()) {
SerialBT.read();
}
delay(500);
// Reset ELM327
SerialBT.println("ATZ");
delay(3000); // Longer delay for reset
String response = "";
while (SerialBT.available()) {
response += (char)SerialBT.read();
}
Serial.println("Reset response: " + response);
// Turn off echo
if (!sendCommand("ATE0", "OK")) {
Serial.println("Echo off failed");
return false;
}
delay(PID_DELAY);
// Turn off line feeds
if (!sendCommand("ATL0", "OK")) {
Serial.println("Line feeds off failed");
// Continue anyway, not critical
}
delay(PID_DELAY);
// Turn off spaces
if (!sendCommand("ATS0", "OK")) {
Serial.println("Spaces off failed");
// Continue anyway, not critical
}
delay(PID_DELAY);
// Set timeout to longer value for older cars
if (!sendCommand("ATST96", "OK")) {
Serial.println("Timeout setting failed");
// Continue anyway
}
delay(PID_DELAY);
// Try specific protocols for 1997 Jeep
// First try ISO 9141-2 (protocol 3)
SerialBT.println("ATSP3");
delay(1000);
response = "";
while (SerialBT.available()) {
response += (char)SerialBT.read();
}
Serial.println("Protocol 3 response: " + response);
// Try a simple PID request to test connection
SerialBT.println("010C"); // RPM request
delay(2000); // Wait longer for older cars
response = "";
unsigned long startTime = millis();
while (millis() - startTime < 5000 && SerialBT.available()) {
response += (char)SerialBT.read();
}
Serial.println("RPM test response: " + response);
if (response.indexOf("410C") != -1 || response.indexOf("41 0C") != -1) {
Serial.println("OBD-II initialization successful with ISO 9141-2!");
return true;
}
// If that fails, try KWP2000 (protocol 2)
SerialBT.println("ATSP2");
delay(1000);
response = "";
while (SerialBT.available()) {
response += (char)SerialBT.read();
}
Serial.println("Protocol 2 response: " + response);
// Try RPM again
SerialBT.println("010C");
delay(2000);
response = "";
startTime = millis();
while (millis() - startTime < 5000 && SerialBT.available()) {
response += (char)SerialBT.read();
}
Serial.println("RPM test response (protocol 2): " + response);
if (response.indexOf("410C") != -1 || response.indexOf("41 0C") != -1) {
Serial.println("OBD-II initialization successful with KWP2000!");
return true;
}
Serial.println("OBD-II initialization failed - trying auto protocol");
// Last resort: try auto protocol
SerialBT.println("ATSP0");
delay(1000);
SerialBT.println("010C");
delay(3000);
response = "";
startTime = millis();
while (millis() - startTime < 5000 && SerialBT.available()) {
response += (char)SerialBT.read();
}
if (response.indexOf("410C") != -1 || response.indexOf("41 0C") != -1) {
Serial.println("OBD-II initialization successful with auto protocol!");
return true;
}
return false;
}
Should we start a new thread just for this project? I don’t want to further muck up the original idea here.
Here's the whole thing. I must stress to you that I'm 90% sure it isn't working as-is.
C++:
#include <BluetoothSerial.h>
#include <LiquidCrystal_I2C.h>
// Initialize Bluetooth Serial and LCD
BluetoothSerial SerialBT;
LiquidCrystal_I2C lcd(0x27, 16, 2); // I2C address 0x27, 16 chars, 2 lines
// ELM327 Communication
String elm327_mac = ""; // Leave empty to connect to any ELM327
bool elm327_connected = false;
bool obd_initialized = false;
// OBD-II PID definitions
#define PID_RPM 0x0C
#define PID_ENGINE_TEMP 0x05
#define PID_VEHICLE_SPEED 0x0D
#define PID_THROTTLE_POS 0x11
// Display variables
unsigned long lastUpdate = 0;
const unsigned long updateInterval = 2000; // Update every 2 seconds (slower for older cars)
const int LED_PIN = 2;
const int PID_DELAY = 300;
// Data storage
int rpm = 0;
int engineTemp = 0;
int vehicleSpeed = 0;
int throttlePos = 0;
// Function declarations
void connectToELM327();
bool initializeOBD();
bool sendCommand(String command, String expectedResponse);
String sendCommandWithResponse(String command);
void updateOBDData();
void updateDisplay();
int hexToDec(String hexStr);
String cleanResponse(String response);
void setup() {
Serial.begin(115200);
// Initialize LED
pinMode(LED_PIN, OUTPUT);
// Initialize LCD
lcd.init();
lcd.backlight();
lcd.setCursor(0, 0);
lcd.print("OBD-II Monitor");
lcd.setCursor(0, 1);
lcd.print("Starting...");
Serial.println("ESP32 OBD-II Monitor Starting...");
// Initialize Bluetooth in master mode
if (!SerialBT.begin("ESP32_OBD_Client", true)) {
Serial.println("Bluetooth initialization failed!");
lcd.clear();
lcd.setCursor(0, 0);
lcd.print("BT Init Failed");
while(1);
}
Serial.println("Bluetooth initialized. Searching for ELM327...");
lcd.clear();
lcd.setCursor(0, 0);
lcd.print("Searching ELM327");
// Connect to ELM327
connectToELM327();
}
void loop() {
// Check if we need to reconnect
if (!elm327_connected) {
digitalWrite(LED_PIN, LOW);
lcd.clear();
lcd.setCursor(0, 0);
lcd.print("Bluetooth connection lost.");
lcd.setCursor(1, 0);
lcd.print("Reconnecting...");
connectToELM327();
delay(1000); // Wait 1 second before retrying
return;
}
// Initialize OBD if not done
if (!obd_initialized) {
if (initializeOBD()) {
obd_initialized = true;
lcd.clear();
lcd.setCursor(0, 0);
lcd.print("OBD Connected");
delay(1000);
} else {
delay(1000); // Wait longer before retrying
return;
}
}
// Update data at regular intervals
if (millis() - lastUpdate >= updateInterval) {
updateOBDData();
lastUpdate = millis();
}
// Update LCD display
updateDisplay();
delay(200); // Longer delay for older OBD systems
}
void connectToELM327() {
Serial.println("Attempting to connect to ELM327...");
// Try to connect to ELM327 (usually named "OBDII" or similar)
if (SerialBT.connect("OBDII") || SerialBT.connect("ELM327") || SerialBT.connect("V1.5")) {
elm327_connected = true;
digitalWrite(LED_PIN, HIGH);
Serial.println("Connected to ELM327!");
lcd.clear();
lcd.setCursor(0, 0);
lcd.print("ELM327 Connected");
delay(2000);
} else {
elm327_connected = false;
digitalWrite(LED_PIN, LOW);
Serial.println("Failed to connect to ELM327");
lcd.clear();
lcd.setCursor(0, 0);
lcd.print("ELM327 Not Found");
lcd.setCursor(0, 1);
lcd.print("Retrying...");
}
}
bool initializeOBD() {
Serial.println("Initializing OBD-II communication...");
// Clear buffer first
while (SerialBT.available()) {
SerialBT.read();
}
delay(500);
// Reset ELM327
SerialBT.println("ATZ");
delay(3000); // Longer delay for reset
String response = "";
while (SerialBT.available()) {
response += (char)SerialBT.read();
}
Serial.println("Reset response: " + response);
// Turn off echo
if (!sendCommand("ATE0", "OK")) {
Serial.println("Echo off failed");
return false;
}
delay(PID_DELAY);
// Turn off line feeds
if (!sendCommand("ATL0", "OK")) {
Serial.println("Line feeds off failed");
// Continue anyway, not critical
}
delay(PID_DELAY);
// Turn off spaces
if (!sendCommand("ATS0", "OK")) {
Serial.println("Spaces off failed");
// Continue anyway, not critical
}
delay(PID_DELAY);
// Set timeout to longer value for older cars
if (!sendCommand("ATST96", "OK")) {
Serial.println("Timeout setting failed");
// Continue anyway
}
delay(PID_DELAY);
// Try specific protocols for 1997 Jeep
// First try ISO 9141-2 (protocol 3)
SerialBT.println("ATSP3");
delay(1000);
response = "";
while (SerialBT.available()) {
response += (char)SerialBT.read();
}
Serial.println("Protocol 3 response: " + response);
// Try a simple PID request to test connection
SerialBT.println("010C"); // RPM request
delay(2000); // Wait longer for older cars
response = "";
unsigned long startTime = millis();
while (millis() - startTime < 5000 && SerialBT.available()) {
response += (char)SerialBT.read();
}
Serial.println("RPM test response: " + response);
if (response.indexOf("410C") != -1 || response.indexOf("41 0C") != -1) {
Serial.println("OBD-II initialization successful with ISO 9141-2!");
return true;
}
// If that fails, try KWP2000 (protocol 2)
SerialBT.println("ATSP2");
delay(1000);
response = "";
while (SerialBT.available()) {
response += (char)SerialBT.read();
}
Serial.println("Protocol 2 response: " + response);
// Try RPM again
SerialBT.println("010C");
delay(2000);
response = "";
startTime = millis();
while (millis() - startTime < 5000 && SerialBT.available()) {
response += (char)SerialBT.read();
}
Serial.println("RPM test response (protocol 2): " + response);
if (response.indexOf("410C") != -1 || response.indexOf("41 0C") != -1) {
Serial.println("OBD-II initialization successful with KWP2000!");
return true;
}
Serial.println("OBD-II initialization failed - trying auto protocol");
// Last resort: try auto protocol
SerialBT.println("ATSP0");
delay(1000);
SerialBT.println("010C");
delay(3000);
response = "";
startTime = millis();
while (millis() - startTime < 5000 && SerialBT.available()) {
response += (char)SerialBT.read();
}
if (response.indexOf("410C") != -1 || response.indexOf("41 0C") != -1) {
Serial.println("OBD-II initialization successful with auto protocol!");
return true;
}
return false;
}
bool sendCommand(String command, String expectedResponse) {
// Clear any existing data
while (SerialBT.available()) {
SerialBT.read();
}
// Send command
SerialBT.println(command);
Serial.println("Sent: " + command);
// Wait for response
String response = "";
unsigned long startTime = millis();
while (millis() - startTime < 4000) { // 4 second timeout
if (SerialBT.available()) {
char c = SerialBT.read();
response += c;
if (response.indexOf(expectedResponse) != -1) {
Serial.println("Received: " + response);
return true;
}
}
}
Serial.println("Command timeout or unexpected response: " + response);
return false;
}
String sendCommandWithResponse(String command) {
// Clear any existing data
while (SerialBT.available()) {
SerialBT.read();
}
// Send command
SerialBT.println(command);
Serial.println("Sent: " + command);
// Wait for response
String response = "";
unsigned long startTime = millis();
while (millis() - startTime < 5000) { // 5 second timeout for data commands
if (SerialBT.available()) {
char c = SerialBT.read();
response += c;
}
// Check if we have a complete response
if (response.indexOf('>') != -1 || response.length() > 20) {
break;
}
}
// Clean up response
response = cleanResponse(response);
Serial.println("Received: " + response);
return response;
}
String cleanResponse(String response) {
response.replace("\r", "");
response.replace("\n", "");
response.replace(">", "");
response.replace(" ", "");
response.toUpperCase();
return response;
}
void updateOBDData() {
// Read RPM (PID 0x0C)
String response = sendCommandWithResponse("010C");
if (response.length() >= 6 && response.substring(0, 4) == "410C") {
String rpmHex = response.substring(4);
if (rpmHex.length() >= 4) {
rpm = (hexToDec(rpmHex.substring(0, 2)) * 256 + hexToDec(rpmHex.substring(2, 4))) / 4;
}
}
delay(300); // Give ELM327 time between commands
// Read Engine Temperature (PID 0x05)
response = sendCommandWithResponse("0105");
if (response.length() >= 6 && response.substring(0, 4) == "4105") {
String tempHex = response.substring(4);
if (tempHex.length() >= 2) {
int tempC = hexToDec(tempHex.substring(0, 2)) - 40; // Convert to Celsius first
engineTemp = (tempC * 9 / 5) + 32; // Convert to Fahrenheit
}
}
delay(300); // Give ELM327 time between commands
// Read Vehicle Speed (PID 0x0D) - may not be supported on 1997 Jeep
response = sendCommandWithResponse("010D");
if (response.length() >= 6 && response.substring(0, 4) == "410D") {
String speedHex = response.substring(4);
if (speedHex.length() >= 2) {
int speedKmh = hexToDec(speedHex.substring(0, 2));
vehicleSpeed = (speedKmh * 10) / 16; // Convert km/h to mph (multiply by 0.621371, simplified)
}
} else {
vehicleSpeed = -1; // Indicate not supported
}
delay(300); // Give ELM327 time between commands
// Read Throttle Position (PID 0x11) - may not be supported on 1997 Jeep
response = sendCommandWithResponse("0111");
if (response.length() >= 6 && response.substring(0, 4) == "4111") {
String throttleHex = response.substring(4);
if (throttleHex.length() >= 2) {
throttlePos = (hexToDec(throttleHex.substring(0, 2)) * 100) / 255;
}
} else {
throttlePos = -1; // Indicate not supported
}
Serial.printf("RPM: %d, Temp: %dF, Speed: %d mph, Throttle: %d%%\n",
rpm, engineTemp, vehicleSpeed, throttlePos);
}
void updateDisplay() {
lcd.clear();
// Top row: RPM and Temperature
lcd.setCursor(0, 0);
lcd.print("RPM:");
if (rpm > 0) {
lcd.print(rpm);
} else {
lcd.print("N/A");
}
lcd.setCursor(9, 0);
lcd.print("T:");
if (engineTemp > -40) {
lcd.print(engineTemp);
lcd.print("F");
} else {
lcd.print("N/A");
}
// Bottom row: Throttle Position and Vehicle Speed
lcd.setCursor(0, 1);
lcd.print("TP:");
if (throttlePos >= 0) {
lcd.print(throttlePos);
lcd.print("%");
} else {
lcd.print("N/A");
}
lcd.setCursor(9, 1);
lcd.print("VS:");
if (vehicleSpeed >= 0) {
lcd.print(vehicleSpeed);
} else {
lcd.print("N/A");
}
}
int hexToDec(String hexStr) {
if (hexStr.length() == 0) return 0;
int decimal = 0;
int base = 1;
int len = hexStr.length();
for (int i = len - 1; i >= 0; i--) {
char c = hexStr.charAt(i);
int digit;
if (c >= '0' && c <= '9') {
digit = c - '0';
} else if (c >= 'A' && c <= 'F') {
digit = c - 'A' + 10;
} else if (c >= 'a' && c <= 'f') {
digit = c - 'a' + 10;
} else {
return 0; // Invalid hex character
}
decimal += digit * base;
base *= 16;
}
return decimal;
}Thanks again!
I understand it's probably not working, but I might pick up some tidbits from it. I think I'll be okay for the rest of the code, I have some examples. I just need to get that initialization stuff going.
I understand it's probably not working, but I might pick up some tidbits from it. I think I'll be okay for the rest of the code, I have some examples. I just need to get that initialization stuff going.
@hear, your initialization code did it! It sets a protocol, and I can read values like RPM and coolant temp.
I had to move the J1850 VPW (aka KWP2000) protocol for my 2005 up to try first, because it wouldn't connect if it tried the ISO 9141-2 for your 1997 first. Nor on Auto. The code looks like it should work for each protocol, but no. I'll experiment with that stuff some more.
So far it's just my initial messy code plus your init code. Now to turn it into something useful...
Good idea about starting another thread, if I (or you) get far enough along to have something worth sharing.
I had to move the J1850 VPW (aka KWP2000) protocol for my 2005 up to try first, because it wouldn't connect if it tried the ISO 9141-2 for your 1997 first. Nor on Auto. The code looks like it should work for each protocol, but no. I'll experiment with that stuff some more.
So far it's just my initial messy code plus your init code. Now to turn it into something useful...
Good idea about starting another thread, if I (or you) get far enough along to have something worth sharing.
I see SparkFun has the UART-OBDII boards in stock. Have you received yours, and have you been able to get it working?
I saw one review on SparkFun where the guy got all of the protocols to work on various vehicles, except for J1850 VPW, which is what we need. I might buy one if I can be sure that protocol will work on it.
I got it but I haven't messed with it yet. That would be unfortunate if it doesn't work for our protocol.
I tried the cheap Veepeak Bluetooth one. I got it working, talking with an ESP32. When it works, it's fine. But Bluetooth can be flaky. Maybe it's just this cheap device. It would send a string of gobbledygook once in a while, and sometimes it wouldn't send the right connection values. I got sick of writing lots of code just to verify its working right. Sometimes it required a power cycle before it would behave. I'm about done with Bluetooth.
So I'm thinking about a UART device, but I've only seen the SparkFun one and one other, which seems very similar and costs a bit more.
I even looked inside my USB OBDII device to see if I could bypass the FTDI TTL-to-USB, but it uses the tiniest 0.5mm pitch surface mount chips.
Im gonna bump this thread to get @OldBuzzard to share more about these recent developments.
tell us more!
tell us more!
Ok, I'll get it all rounded up and post it here...
Homebrew OBDII Gauge Set
After messing with writing OBDII reader code for Bluetooth (thanks to @hear for helping to get me started), I got tired of Bluetooth's flakiness. I was writing more code to keep it running than to display OBDII info. I kept having to add error-checking and recovery code for the initial connection, and dropouts, and timeouts, and partial responses. And using a cheapo Bluetooth reader wasn't helping. In the interest of having a permanent in-vehicle OBDII display, which works reliably every day, I switched back to a wired (serial) OBDII reader.
It's a 5G Hub serial OBD board (similar to the SparkFun board, but smaller and includes the 16-pin connector, which costs extra for the SparkFun board). Note: the 5G Hub website is flaky and often fails to respond. I bought it from DigiKey for about $70. Then I had to contact 5G Hub for the custom case, which I think was supposed to come with it.
I have it permanently connected in the Jeep, feeding a RasPi Pico microcontroller and a touch LCD. It works nicely, currently just displaying 6 lines of OBD info. I connected it to a second DLC (Data Link Connector) under the dash via a SPDT switch. That allows it to be completely switched out of the circuit to prevent interference (like when the emissions test guy plugs his reader in). And the second DLC is fed from key-switched power, so the reader completely shuts down when the key is off. Can't kill the battery.
The RasPi Pico is not a typical "real" Raspberry Pi, it's just a microcontroller on a board, similar to an Arduino, about $4. No OS. Not the WiFi version, not v2 or v2-WiFi. I use the Arduino IDE to code and burn it. For a display, I initially I used a Wondiwe 3.5" 480x320 SPI TFT LCD. It worked fine, but was a little hard to read, and the off-axis color shifts were bad. I switched to a much better Hosyond 3.5" 480x320 SPI IPS LCD for about $20 (only slightly more than the TFT version). The IPS LCD is easy to read from any angle, with no color shifts, far better than the more common TFT LCD. It has a capacitive touch panel, which I'm not using in the current firmware.
I built this prototype version with point-to-point wiring on a sea-of-holes PCB. There's not much to it, and it should be straightforward to lay out a real PCB. American PCB fab is pricy. Chinese PCB fab can be quite high quality and dirt cheap, but shipping and tariffs tend to kill the cost savings.
The firmware is just Arduino C code, using the ELMduino library to talk to the OBDII reader, and Bodmer's TFT_eSPI library to drive the LCD. It also uses Bodmer's Adafruit GFX fonts. I modified one of the fonts to replace the fairly useless backtick with a needed degree symbol. The touch panel will use the RAK14014-FT6336U driver when I get around to it.
The LCD console hangs from an overhead rack in the LJ, above the rearview mirror, alongside a backup camera.
Photos, schematics, and source code are included in the attached zip file.
I'm working on a round-gauge library to pretty it up. But I sure don't work as fast as I used to. It will take a while.
The RPi Pico has some free I/O pins. They could be used to read other inputs directly from sensors like oil pressure, and an accelerometer. I've been messing with some graphical inclinometer code, but that's taking even longer than the round-gauge stuff.
After messing with writing OBDII reader code for Bluetooth (thanks to @hear for helping to get me started), I got tired of Bluetooth's flakiness. I was writing more code to keep it running than to display OBDII info. I kept having to add error-checking and recovery code for the initial connection, and dropouts, and timeouts, and partial responses. And using a cheapo Bluetooth reader wasn't helping. In the interest of having a permanent in-vehicle OBDII display, which works reliably every day, I switched back to a wired (serial) OBDII reader.
It's a 5G Hub serial OBD board (similar to the SparkFun board, but smaller and includes the 16-pin connector, which costs extra for the SparkFun board). Note: the 5G Hub website is flaky and often fails to respond. I bought it from DigiKey for about $70. Then I had to contact 5G Hub for the custom case, which I think was supposed to come with it.
I have it permanently connected in the Jeep, feeding a RasPi Pico microcontroller and a touch LCD. It works nicely, currently just displaying 6 lines of OBD info. I connected it to a second DLC (Data Link Connector) under the dash via a SPDT switch. That allows it to be completely switched out of the circuit to prevent interference (like when the emissions test guy plugs his reader in). And the second DLC is fed from key-switched power, so the reader completely shuts down when the key is off. Can't kill the battery.
The RasPi Pico is not a typical "real" Raspberry Pi, it's just a microcontroller on a board, similar to an Arduino, about $4. No OS. Not the WiFi version, not v2 or v2-WiFi. I use the Arduino IDE to code and burn it. For a display, I initially I used a Wondiwe 3.5" 480x320 SPI TFT LCD. It worked fine, but was a little hard to read, and the off-axis color shifts were bad. I switched to a much better Hosyond 3.5" 480x320 SPI IPS LCD for about $20 (only slightly more than the TFT version). The IPS LCD is easy to read from any angle, with no color shifts, far better than the more common TFT LCD. It has a capacitive touch panel, which I'm not using in the current firmware.
I built this prototype version with point-to-point wiring on a sea-of-holes PCB. There's not much to it, and it should be straightforward to lay out a real PCB. American PCB fab is pricy. Chinese PCB fab can be quite high quality and dirt cheap, but shipping and tariffs tend to kill the cost savings.
The firmware is just Arduino C code, using the ELMduino library to talk to the OBDII reader, and Bodmer's TFT_eSPI library to drive the LCD. It also uses Bodmer's Adafruit GFX fonts. I modified one of the fonts to replace the fairly useless backtick with a needed degree symbol. The touch panel will use the RAK14014-FT6336U driver when I get around to it.
The LCD console hangs from an overhead rack in the LJ, above the rearview mirror, alongside a backup camera.
Photos, schematics, and source code are included in the attached zip file.
I'm working on a round-gauge library to pretty it up. But I sure don't work as fast as I used to. It will take a while.
The RPi Pico has some free I/O pins. They could be used to read other inputs directly from sensors like oil pressure, and an accelerometer. I've been messing with some graphical inclinometer code, but that's taking even longer than the round-gauge stuff.
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