ESP32 Wifi: getting weird responses

[hrtkpf]

Hello,

I was testing ELMduino with a OBD2 Wifi adapter and an ESP32. I read #52 and I know there may be problems with this configuration. I'm trying to read the coolant temperature of a BMW from 2014. Sometimes, I get correct numbers, but very often I just get weird responses.
After some debugging, I found out that these "weird responses" might actually contain the correct value but some weird symbols as well, which could be misinterpreted by my code.

I just tested with two different sketches, one by me and the other one being your "ESP32_test.ino", adapted to work with Wifi.
I will only post my sketch and the output for now because I don't want the initial issue to be too long, but I can also post the debug sketch and its output later on if desired.
I also added some comments starting with "NOTE:". Unrelated parts of the sketch, like printing to a display, are omitted.

My sketch:

#include <WiFi.h>
#include <ELMduino.h>

// ELM dongle IP address
IPAddress ELMserver(192, 168, 0, 10);
WiFiClient client;
ELM327 elm;

int lastUpdatedCoolant, updateAgeCoolant = 0;
int coolantTemp = 0;


void setup(){
  Serial.begin(115200);

  WiFi.mode(WIFI_STA);
  WiFi.begin("V-LINK");

  Serial.println("Connecting to WiFi...");

  while (WiFi.status() != WL_CONNECTED){
    Serial.print(".");
    delay(500);
  }

  // could improve wireless connectivity with ESP (maybe)
  client.setNoDelay(true); // NOTE: due to the error in the output, I don't know if this has any influence at all

  if(client.connect(ELMserver, 35000)){
    Serial.println("ELM connected");
  }else{
    Serial.println("ELM connection failed");
    delay(5000);
    ESP.restart();
  }

  elm.begin(client, true);
}


void loop(){
  // Coolant
  float readCoolantTemp = elm.engineCoolantTemp();

  Serial.println(readCoolantTemp);

  if(elm.status == ELM_SUCCESS && readCoolantTemp < 200 && readCoolantTemp >= 0){
    coolantTemp = readCoolantTemp;
    lastUpdatedCoolant = millis();
  }else{
    // NOTE: this fails because the value is too high, but elm.status is actually ELM_SUCCESS
    Serial.println("Could not read Coolant");
    elm.printError();
  }

  if(elm.status == ELM_TIMEOUT){
    ESP.restart();
  }

  updateAgeCoolant = (millis() - lastUpdatedCoolant) / 1000;

  String textCoolant = (String)coolantTemp + " C, " + updateAgeCoolant + "s";
  Serial.println(textCoolant);

  delay(5000);
}

The corresponding output:

Connecting to WiFi...
..[E][WiFiClient.cpp:309] setOption(): fail on fd -1, errno: 9, "Bad file number"
ELM connected
Clearing input serial buffer
Sending the following command/query: AT D
All chars received:
Timeout detected with overflow of 0ms
Clearing input serial buffer
Sending the following command/query: AT Z
Received char: A
Received char: T
Received char:
Received char: Z
Received char: \r
All chars received: ATZ
Timeout detected with overflow of 0ms
Clearing input serial buffer
Sending the following command/query: AT E0
Received char: A
Received char: T
Received char:
Received char: E
Received char: 0
Received char: \r
Received char: O
Received char: K
Received char: \r
Received char: \r
Received char: >
Delimiter found
All chars received: ATE0OK
Clearing input serial buffer
Sending the following command/query: AT S0
Received char: O
Received char: K
Received char: \r
Received char: \r
Received char: >
Delimiter found
All chars received: OK
Clearing input serial buffer
Sending the following command/query: AT AL
Received char: O
Received char: K
Received char: \r
Received char: \r
Received char: >
Delimiter found
All chars received: OK
Clearing input serial buffer
Sending the following command/query: AT TP A0
Received char: O
Received char: K
Received char: \r
Received char: \r
Received char: >
Delimiter found
All chars received: OK
Service: 1
PID: 5
Normal length query detected
Query string: 0105
Clearing input serial buffer
Sending the following command/query: 0105
Received char: S
Received char: E
Received char: A
Received char: R
Received char: C
Received char: H
Received char: I
Received char: N
Received char: G
Received char: .
Received char: .
Received char: .
Received char: \r
Received char: �
Received char: 4
Received char: 1
Received char: 0
Received char: 5
Received char: 2
Received char: 8
Received char: \r
Received char: �
Received char: \r
Received char: >
Delimiter found
All chars received: SEARCHING...�410528�
Expected response header: 4105
Single response detected
64-bit response: responseByte_0: 200
responseByte_1: 2
responseByte_2: 0
responseByte_3: 0
responseByte_4: 0
responseByte_5: 0
responseByte_6: 0
responseByte_7: 0
672.00 // NOTE: even though the ELM response seems to be correct, the interpreted value is way too high
Could not read Coolant
Received: SEARCHING...�410528� // NOTE: First response includes "SEARCHING...", the numbers seem to be correct but also contain the "weird symbols"
ELM_SUCCESS
0 C, 10s // NOTE: coolant temp is 0 here because coolantTemp is initialized with 0
Service: 1
PID: 5
Normal length query detected
Query string: 0105
Clearing input serial buffer
Sending the following command/query: 0105
Received char: 4
Received char: 1
Received char: 0
Received char: 5
Received char: 2
Received char: 8
Received char: \r
Received char: �
Received char: \r
Received char: >
Delimiter found
All chars received: 410528�
Expected response header: 4105
Single response detected
64-bit response: responseByte_0: 200
responseByte_1: 2
responseByte_2: 0
responseByte_3: 0
responseByte_4: 0
responseByte_5: 0
responseByte_6: 0
responseByte_7: 0
672.00
Could not read Coolant
Received: 410528�
ELM_SUCCESS
0 C, 16s
Service: 1
PID: 5
Normal length query detected
Query string: 0105
Clearing input serial buffer
Sending the following command/query: 0105
Received char: 4
Received char: 1
Received char: 0
Received char: 5
Received char: 2
Received char: 8
Received char: \r
Received char: �
Received char: \r
Received char: >
Delimiter found
All chars received: 410528�
Expected response header: 4105
Single response detected
64-bit response: responseByte_0: 200
responseByte_1: 2
responseByte_2: 0
responseByte_3: 0
responseByte_4: 0
responseByte_5: 0
responseByte_6: 0
responseByte_7: 0
672.00
Could not read Coolant
Received: 410528�
ELM_SUCCESS
0 C, 22s
Service: 1
PID: 5
Normal length query detected
Query string: 0105
Clearing input serial buffer
Sending the following command/query: 0105
Received char: 4
Received char: 1
Received char: 0
Received char: 5
Received char: 2
Received char: 8
Received char: \r
Received char: �
Received char: \r
Received char: >
Delimiter found
All chars received: 410528�
Expected response header: 4105
Single response detected
64-bit response: responseByte_0: 200
responseByte_1: 2
responseByte_2: 0
responseByte_3: 0
responseByte_4: 0
responseByte_5: 0
responseByte_6: 0
responseByte_7: 0
672.00
Could not read Coolant
Received: 410528�
ELM_SUCCESS
0 C, 28s
Service: 1
PID: 5
Normal length query detected
Query string: 0105
Clearing input serial buffer
Sending the following command/query: 0105
Received char: 4
Received char: 1
Received char: 0
Received char: 5
Received char: 2
Received char: 8
Received char: \r
Received char: �
Received char: \r
Received char: >
Delimiter found
All chars received: 410528�
Expected response header: 4105
Single response detected
64-bit response: responseByte_0: 200
responseByte_1: 2
responseByte_2: 0
responseByte_3: 0
responseByte_4: 0
responseByte_5: 0
responseByte_6: 0
responseByte_7: 0
672.00
Could not read Coolant
Received: 410528�
ELM_SUCCESS
0 C, 33s
Service: 1
PID: 5
Normal length query detected
Query string: 0105
Clearing input serial buffer
Sending the following command/query: 0105
Received char: 4
Received char: 1
Received char: 0
Received char: 5
Received char: 2
Received char: 8
Received char: \r
Received char: �
Received char: \r
Received char: >
Delimiter found
All chars received: 410528�
Expected response header: 4105
Single response detected
64-bit response: responseByte_0: 200
responseByte_1: 2
responseByte_2: 0
responseByte_3: 0
responseByte_4: 0
responseByte_5: 0
responseByte_6: 0
responseByte_7: 0
672.00
Could not read Coolant
Received: 410528�
ELM_SUCCESS
0 C, 39s
Service: 1
PID: 5
Normal length query detected
Query string: 0105
Clearing input serial buffer
Sending the following command/query: 0105
Received char: 4
Received char: 1
Received char: 0
Received char: 5
Received char: 2
Received char: 8
Received char: \r
Received char: �
Received char: \r
Received char: >
Delimiter found
All chars received: 410528�
Expected response header: 4105
Single response detected
64-bit response: responseByte_0: 200
responseByte_1: 2
responseByte_2: 0
responseByte_3: 0
responseByte_4: 0
responseByte_5: 0
responseByte_6: 0
responseByte_7: 0
672.00
Could not read Coolant
Received: 410528�
ELM_SUCCESS
0 C, 44s

Sometimes, I get the correct number (without the weird symbols) which is then correctly interpreted by the code, but while logging this output, that didn't work.
Thanks to this page, I was able to manually decode the response values (after removing weird symbols) and they correctly decode to 0 °C in this case.

Do you think those weird symbols originate from hardware issues like described in #52? Like I said, the raw numbers seem to be correct.
Also, thank you for maintaining this very useful library! :)

[PowerBroker2]

I don't know why you're getting the � char, but I'll add a filter in the parsing function to throw out any non-alphanumeric ascii chars. This should fix your issue

Also, thank you for maintaining this very useful library! :)

Happy to help and really appreciate people find it useful!

[PowerBroker2]

Try testing the main branch. If it works I'll tag out a new version. If not, please post the latest debug printout

[hrtkpf]

Thank you for your fast response! I will test the code tomorrow again and report back ASAP.

But doesn’t it need to be !isalnum(recChar) because we want to continue on non-alphanumerical chars? Or am I overseeing something?

[hrtkpf]

So I just tested the updated code and it works flawlessly now! Apparently no hardware issues, just some timeouts here and there, but that's probably normal.

Thank you!

[PowerBroker2]

Fixed in release 2.5.5