how to read OBDII voltage in sketch on Arduino IDE

[powerbroker2]

how to read OBDII voltage in sketch on Arduino IDE

[PowerBroker2]

What do you get if you use this code?

Serial.print("Batt: "); 
myELM327.sendCommand(READ_VOLTAGE);
Serial.write(myELM327.payload, myELM327.recBytes)
Serial.println("V");

[lysiong]

Thanks for reply, I will try tonight & let you know the result.

[lysiong]

@PowerBroker2 ,
seem like the code not working, it stuck at below code

Serial.write(myELM327.payload, myELM327.recBytes)

error message below

ESP32_Bluetooth_Serial:56:23: error: invalid conversion from 'char*' to 'const uint8_t* {aka const unsigned char*}' [-fpermissive]

Serial.write(myELM327.payload, myELM327.recBytes)

                   ^

I was using the example from your library ESP32_Bluetooth_Serial.ino
remark out the below 3 lines

float tempRPM = myELM327.rpm();
rpm = (uint32_t)tempRPM;
Serial.print("RPM: "); Serial.println(rpm);

& add in the command that you give after the below command

if (myELM327.status == ELM_SUCCESS)

Serial.print("Batt: ");
myELM327.sendCommand(READ_VOLTAGE);
Serial.write(myELM327.payload, myELM327.recBytes);
Serial.println("V");

Just found up if I modify the code become like below, it works !!
Serial.print("Batt: ");
myELM327.sendCommand(READ_VOLTAGE);
Serial.write(myELM327.payload);
Serial.println(" ");

Result in serial monitor as below
Batt: 12.2V <--I not sure where the V coming from ........

But if I change the code to below
Serial.print("Batt: ");
myELM327.sendCommand(READ_VOLTAGE);
Serial.write(myELM327.recBytes);
Serial.println(" ");

Result in serial monitor as below
Batt: � <--I not sure what is generate out, is like a square symbol.

So the data is in payload? what is recBytes store actually?

[PowerBroker2]

Sorry about the error, I forgot the ESP32 handles Serial.write() strangely. Try this instead:

Serial.print("Batt: "); 
myELM327.sendCommand(READ_VOLTAGE);
Serial.write((const uint8_t*)myELM327.payload, (uint8_t)myELM327.recBytes)
Serial.println("V");

myELM327.payload is a buffer for the characters returned from the ELM327 and myELM327.recBytes is the total number of characters returned from the ELM327 and stuffed in the buffer myELM327.payload.

[lysiong]

seem like the result is same for below 2 command,

Serial.write(myELM327.payload);
Serial.write((const uint8_t*)myELM327.payload, (uint8_t)myELM327.recBytes)
Batt: 12.1vv <-- ya, double V somehow, I just remove the print V command.

but if I print the result to LCD screen using (myELM327.payload), then the result is different.
LCD screen will show below
ATRV12.1v <--show the ATRV command in front although I didnt specify it.

[PowerBroker2]

Looks like the library is working as intended - the LCD portion depends on your code. Can you confirm?

[lysiong]

for the LCD portion, I just code it as below
lcd.print(myELM327.payload);

maybe need to add the filter for filter up the ATRV wording? I'm still very new to this coding, will take sometime to dig it or you have any idea?

[PowerBroker2]

Maybe. Can you post your entire sketch?

[lysiong]

I'm simplify my code as below, LCD library take from https://github.com/Bodmer/TFT_eSPI
the LCD will display result as below
OBD voltage: ATRV12.4V

#include <TFT_eSPI.h> 
#include "BluetoothSerial.h"
#include "ELMduino.h"

TFT_eSPI lcd = TFT_eSPI();  

#define BLK     0x0000

BluetoothSerial SerialBT;
#define ELM_PORT   SerialBT
#define DEBUG_PORT Serial
ELM327 myELM327;


void setup() 
{
  lcd.init();
  lcd.fillScreen(BLK);
  lcd.setRotation(1);

  lcd.setTextSize(3);

  Serial.begin(115200);
  ELM_PORT.begin("ArduHUD", true);
  
  if (!ELM_PORT.connect("OBDLink LX"))
  {
    DEBUG_PORT.println("Couldn't connect to OBD scanner - Phase 1");
    while(1);
  }

  if (!myELM327.begin(ELM_PORT))
  {
    Serial.println("Couldn't connect to OBD scanner - Phase 2");
    while (1);
  }

  Serial.println("Connected to ELM327");
}


void loop()
{
 lcd.setCursor(0, 0, 1);
    lcd.print("OBD voltage: ");
    myELM327.sendCommand(READ_VOLTAGE);
    lcd.print(myELM327.payload);
}

[PowerBroker2]

That sketch doesn't send any manual AT commands. Please update your comment with the correct sketch.

[lysiong]

That sketch doesn't send any manual AT commands. Please update your comment with the correct sketch.

@PowerBroker2 sorry, I forgot to add in the below line. Please find the update comment above.
myELM327.sendCommand(READ_VOLTAGE);

[PowerBroker2]

Try lcd.write(myELM327.payload, myELM327.recBytes)

[lysiong]

Will try tonight & let you know the results

[lysiong]

using both command below also come out the same error
lcd.write(myELM327.payload, myELM327.recBytes)
lcd.print(myELM327.payload, myELM327.recBytes)

no matching function for call to 'TFT_eSPI::write(char*&, uint16_t&)'

I will try to figure out as your library is actually working.

[PowerBroker2]

Ok, sounds good. You'll probably find more help if you post on the Arduino forum.