[I2C] MLX90614 temp sensor not working over ESP32 I2C interface

[marquesn]

Hardware:

Board: ESP-WROOM-32 (ESP32_DevKitc_V4)
Core Installation version: 1.0.1
IDE name: Arduino IDE
Flash Frequency: 80Mhz
PSRAM enabled: No
Upload Speed: 921600
Computer OS: Windows 10

Description:

I have been trying to get a MLX90614 IR temperature sensor to work with the ESP32 - this sensor makes use of the I2C interface. However, the values are always reported back as 1037 C and 1899F.

I have been using pins 22 and 21 for SCL and SDA, and have tried supplying the sensor with both 3.3V and 5V. I have also connected 4.7K pull-up resistors to the SDA and SCL lines (also tried 2K7, 10K, and with no pull-ups).

I am using the "Adafruit_MLX90614" library, and have also tried to use the Sparkfun MLX90614 (although Sparkfun is giving me a compiling error when trying to compile for the ESP32). I have also tried to connect another MLX90614 to the ESP32 on the off chance that one of them might've just been broken, but the results were the same.

I have also seen similar issues to this as in:
#1694
#2089
#1962

Based on the solutions provided in the links shown above, I also tried to update the latest version of the arduino-esp32 using the arduino boards manager to version 1.0.1.

Sketch:

#include <Wire.h>
#include <Adafruit_MLX90614.h>
 
Adafruit_MLX90614 mlx = Adafruit_MLX90614();
 
void setup()
{
  Serial.begin(9600);
  mlx.begin();
}
 
void loop()
{
  Serial.print("Ambient = ");
  Serial.print(mlx.readAmbientTempC());
  Serial.print("*C\tObject = ");
  Serial.print(mlx.readObjectTempC());
  Serial.println("*C");
  Serial.print("Ambient = ");
  Serial.print(mlx.readAmbientTempF());
  Serial.print("*F\tObject = ");
  Serial.print(mlx.readObjectTempF());
  Serial.println("*F");
   
  Serial.println();
  delay(1000);
}

[marquesn]

I've been struggling with this issue for almost a week now and have tried all I2C and Wire files from the latest version of this repo. Would very much appreciate some feedback on this....

[stickbreaker]

@marquesn I don't have access to MLX90614 so I can't directly test it.

I looked at the adafruit library, it is very simple and does not test for any error codes / i2c failure codes.

I recommend you add debug code to your copy of the library and see what errors are being returned by i2c(Wire).

Change every Wire.endTransmission() into:

uint_8 err = Wire.endTransmission();
if(err != 0) {
  Serial.printf("fail %d(%s)/n",err, Wire.getErrorText(err));
}

// after each requestFrom() add
if(Wire.lastError() !=0 ){
Serial.printf("fail %d(%s)/n",err, Wire.getErrorText(err));
}

See what is actually happening.

Chuck.

[marquesn]

@stickbreaker Many thanks for having a look at this!

I've inserted that piece of code into the Adafruit library and I got the following in the serial output window:

ɭշ⸮⸮8⸮"/-n^.p⸮�⸮⸮5Q⸮N⸮⸮⸮[V][esp32-hal-i2c.c:1483] i2cInit(): num=0 sda=21 scl=22 freq=0
[V][esp32-hal-i2c.c:1677] i2cSetFrequency(): freq=100000Hz
[V][esp32-hal-i2c.c:1692] i2cSetFrequency(): cpu Freq=240Mhz, i2c Freq=100000Hz
[V][esp32-hal-i2c.c:1698] i2cSetFrequency(): Fifo delta=1
fail 2(ACK)/nfail 2(ACK)/n1037.55*C
Ambient = fail 2(ACK)/nfail 2(ACK)/n1899.59*F	Object = fail 2(ACK)/nfail 2(ACK)/n1899.59*F

Ambient = fail 2(ACK)/nfail 2(ACK)/n1037.55*C	Object = fail 2(ACK)/nfail 2(ACK)/n1037.55*C
Ambient = fail 2(ACK)/nfail 2(ACK)/n1899.59*F	Object = fail 2(ACK)/nfail 2(ACK)/n1899.59*F

[marquesn]

There was only one

Wire.endTransmission(false);

But if instead of:

uint8_t err = Wire.endTransmission();

I change it to:

uint8_t err = Wire.endTransmission(false);

I get the following:

⸮⸮⸮⸮⸮⸮8⸮⸮2⸮⸮Շ⸮⸮i�Q⸮qm⸮555ԡx⸮⸮⸮⸮⸮⸮⸮⸮[V][esp32-hal-i2c.c:1483] i2cInit(): num=0 sda=21 scl=22 freq=0
[V][esp32-hal-i2c.c:1677] i2cSetFrequency(): freq=100000Hz
[V][esp32-hal-i2c.c:1692] i2cSetFrequency(): cpu Freq=240Mhz, i2c Freq=100000Hz
[V][esp32-hal-i2c.c:1698] i2cSetFrequency(): Fifo delta=1
=Ambient = fail 0(OK)/n1037.55*C	Object = fail 0(OK)/n1037.55*C
Ambient = fail 0(OK)/n1899.59*F	Object = fail 0(OK)/n1899.59*F

Ambient = fail 0(OK)/n1037.55*C	Object = fail 0(OK)/n1037.55*C
Ambient = fail 0(OK)/n1899.59*F	Object = fail 0(OK)/n1899.59*F

[stickbreaker]

@marquesn ok, that is telling you the I2C communication succeeded.
now you need to look at the data it received.
Write out the raw data byte from the sensor.

 // where it receives data with Wire.read(), print the raw byte out
uint16_t Adafruit_MLX90614::read16(uint8_t a) {
  uint16_t ret;

  Wire.beginTransmission(_addr); // start transmission to device 
  Wire.write(a); // sends register address to read from
  uint8_t err =  Wire.endTransmission(false); // end transmission
  if(err !=0){
    Serial.printf("Selecting sensor register failed =%d(%s)\n",err, Wire.getErrorText(err)));
  }
  uint8_t count =Wire.requestFrom(_addr, (uint8_t)3);// send data n-bytes read
  If(count != 3){
    Serial.printf("Receiving sensor data failed, expected 3 bytes received %d.\n Wire() error =%d(%s)\n",
     count,Wire.lastError(),Wire.getErrorText(Wire.lastError()));
  }
  uint8_t raw = Wire.read();
  Serial.printf(" first byte = 0x%02x",raw);
  ret = raw; // receive DATA
  raw = Wire.read();
   Serial.printf(" Second Byte = 0x%02x\n",raw);
  ret |= raw << 8; // receive DATA

  uint8_t pec = Wire.read();
  Serial.printf(" pec=0x%02x\n", pec);
  return ret;
}

Chuck.

[marquesn]

@marquesn ok, that is telling you the I2C communication succeeded.
now you need to look at the data it received.
Write out the raw data byte from the sensor.

 // where it receives data with Wire.read(), print the raw byte out
uint16_t Adafruit_MLX90614::read16(uint8_t a) {
  uint16_t ret;

  Wire.beginTransmission(_addr); // start transmission to device 
  Wire.write(a); // sends register address to read from
  uint8_t err =  Wire.endTransmission(false); // end transmission
  if(err !=0){
    Serial.printf("Selecting sensor register failed =%d(%s)\n",err, Wire.getErrorText(err)));
  }
  uint8_t count =Wire.requestFrom(_addr, (uint8_t)3);// send data n-bytes read
  If(count != 3){
    Serial.printf("Receiving sensor data failed, expected 3 bytes received %d.\n Wire() error =%d(%s)\n",
     count,Wire.lastError(),Wire.getErrorText(Wire.lastError()));
  }
  uint8_t raw = Wire.read();
  Serial.printf(" first byte = 0x%02x",raw);
  ret = raw; // receive DATA
  raw = Wire.read();
   Serial.printf(" Second Byte = 0x%02x\n",raw);
  ret |= raw << 8; // receive DATA

  uint8_t pec = Wire.read();
  Serial.printf(" pec=0x%02x\n", pec);
  return ret;
}

Chuck.

Thanks Chuck. This code gives me the following:

[V][esp32-hal-i2c.c:1483] i2cInit(): num=0 sda=21 scl=22 freq=0
[V][esp32-hal-i2c.c:1677] i2cSetFrequency(): freq=100000Hz
[V][esp32-hal-i2c.c:1692] i2cSetFrequency(): cpu Freq=240Mhz, i2c Freq=100000Hz
[V][esp32-hal-i2c.c:1698] i2cSetFrequency(): Fifo delta=1
Receiving sensor data failed, expected 3 bytes received 0.
 Wire() error =2(ACK)
 first byte = 0xff Second Byte = 0xff
 pec=0xff
1037.55*C
Ambient = Receiving sensor data failed, expected 3 bytes received 0.
 Wire() error =2(ACK)
 first byte = 0xff Second Byte = 0xff
 pec=0xff
1899.59*F	Object = Receiving sensor data failed, expected 3 bytes received 0.
 Wire() error =2(ACK)
 first byte = 0xff Second Byte = 0xff
 pec=0xff
1899.59*F

But changing:

uint8_t err =  Wire.endTransmission(false); // end transmission

to:

uint8_t err =  Wire.endTransmission(); // end transmission

gives me:

[V][esp32-hal-i2c.c:1483] i2cInit(): num=0 sda=21 scl=22 freq=0
[V][esp32-hal-i2c.c:1677] i2cSetFrequency(): freq=100000Hz
[V][esp32-hal-i2c.c:1692] i2cSetFrequency(): cpu Freq=240Mhz, i2c Freq=100000Hz
[V][esp32-hal-i2c.c:1698] i2cSetFrequency(): Fifo delta=1
1037.55*C	Object = Selecting sensor register failed =2(ACK)
Receiving sensor data failed, expected 3 bytes received 0.
 Wire() error =2(ACK)
 first byte = 0xff Second Byte = 0xff
 pec=0xff
1037.55*C
Ambient = Selecting sensor register failed =2(ACK)
Receiving sensor data failed, expected 3 bytes received 0.
 Wire() error =2(ACK)
 first byte = 0xff Second Byte = 0xff
 pec=0xff
1899.59*F	Object = Selecting sensor register failed =2(ACK)
Receiving sensor data failed, expected 3 bytes received 0.
 Wire() error =2(ACK)
 first byte = 0xff Second Byte = 0xff
 pec=0xff
1899.59*F

Seems like the "false" keyword in wire.endtransmission() prints out another line - "Ambient = Selecting sensor register failed =2(ACK)". Besides that, everything else seems the same.

[stickbreaker]

The Error 2, ACK is telling you the sensor did not respond when the ESP32 sent out it's request.. Since it did not respond, no data was received. the 0xff is the response from Wire.read() when no data is available.

The code that produces this:

=Ambient = fail 0(OK)/n1037.55*C	Object = fail 0(OK)/n1037.55*C
Ambient = fail 0(OK)/n1899.59*F	Object = fail 0(OK)/n1899.59*F

Ambient = fail 0(OK)/n1037.55*C	Object = fail 0(OK)/n1037.55*C
Ambient = fail 0(OK)/n1899.59*F	Object = fail 0(OK)/n1899.59*F

the (ok) shows that the device can answer.

does your circuit had 3.3k pullups on SCL and SDA?

Once you can get no errors reported by Wire() then we can see what the data conversion problems are.

Chuck.

[marquesn]

I see... I have 4.7K pull-ups on the SCL and SDA lines.

I believe I had tried other resistor values as well, but I will try again when I get back to the office, and I'll report back here with the results.

Once again, thanks for the clarifications @stickbreaker

[AbaloneIron]

@marquesn I am having the same problem and due to a lack of time and/or tenacity am awaiting with bated breath.

Thanks

[marquesn]

@stickbreaker I have just tried this with the 3.3K pull-ups but the result is the same:

[V][esp32-hal-i2c.c:1483] i2cInit(): num=0 sda=21 scl=22 freq=0
[V][esp32-hal-i2c.c:1677] i2cSetFrequency(): freq=100000Hz
[V][esp32-hal-i2c.c:1692] i2cSetFrequency(): cpu Freq=240Mhz, i2c Freq=100000Hz
[V][esp32-hal-i2c.c:1698] i2cSetFrequency(): Fifo delta=1
Receiving sensor data failed, expected 3 bytes received 0.
 Wire() error =2(ACK)
 first byte = 0xff Second Byte = 0xff
 pec=0xff
1037.55*C
Ambient = Receiving sensor data failed, expected 3 bytes received 0.
 Wire() error =2(ACK)
 first byte = 0xff Second Byte = 0xff
 pec=0xff
1899.59*F	Object = Receiving sensor data failed, expected 3 bytes received 0.
 Wire() error =2(ACK)
 first byte = 0xff Second Byte = 0xff
 pec=0xff
1899.59*F

Also just tried it with the other MLX sensor that I have, as well as with another ESP32 of the same model, and the results were the same.

Just in case I may be doing something wrong with with the debug code in the Adafruit library, here is a pastebin link of my Adafruit_MLX90614.cpp library after substituting in the debug code that you provided:

https://pastebin.com/WBr8Bihy

[marquesn]

Does anyone else have any other ideas regarding this issue?

[asetyde]

I've same problem with SHT21 value is not correct, probably all is linked to cpu/i2c relationship I think, this part of code is changed, test if, as I, with previous releases work

[elasly]

I am having the exact same issue with the same versions of libraries, Any one figured the reason behind this or how to solve it. Thanks in advance

[martinlaurentfr]

As i m a noob, I've been spending days and days to find a solution on this.
It seems defaut frequency of this thing is not the right one, when i specified it, the probleme disepeared

i2c = machine.I2C(scl=machine.Pin(sdaPin), sda=machine.Pin(sclPin),freq=100000)

All other sensor worked on the i2c bus on the same time, without this freq specification, but Mlx didn't

Didn' t used the Adafruit librarys but hope it can help