How to interface MLX90614 temperature sensor with Raspberry Pi

Question

I have a mlx90614 sensor and I am interfacing it with raspberry pi 3 B+. I am using adafruit library python. Below is the code:

import Adafruit_GPIO.I2C as I2C

I2C.require_repeated_start()

class Melexis:

    def __init__(self, address=0x5A):
        self._i2c = I2C.Device(address,busnum=1)

    def readAmbient(self):
        return self._readTemp(0x06)

    def readObject1(self):
        return self._readTemp(0x07)

    def readObject2(self):
        return self._readTemp(0x08)

    def _readTemp(self, reg):
        temp = self._i2c.readS16(reg)
        print("raw temp {}".format(temp))
        temp = temp * .02 - 273.15
        return temp

sensor = Melexis()
t = sensor.readObject1()
a = sensor.readAmbient()
print("Object: {}C , Ambiant: {}C".format(round(t, 3), round(a, 3)))

Output:

raw temp 0
raw temp 0
Object: -273.15C , Ambiant: -273.15C

I have connected the sda pin of sensor to sda pin 3 of pi and scl pin of sensor to scl pin 5 of pi. vcc to 3.3v pin 1 and gnd to gnd. But I am not able to read the temperature values and it only shows 0*c. I have checked the output of ls /dev and I can see the i2c device connected as i2c-1. When I am doing i2cdetect -y 1, I am getting below output:

0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f
10: 10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f
20: 20 21 22 23 24 25 26 27 28 29 2a 2b 2c 2d 2e 2f
30: 30 31 32 33 34 35 36 37 38 39 3a 3b 3c 3d 3e 3f
40: 40 41 42 43 44 45 46 47 48 49 4a 4b 4c 4d 4e 4f
50: 50 51 52 53 54 55 56 57 58 59 5a 5b 5c 5d 5e 5f
60: 60 61 62 63 64 65 66 67 68 69 6a 6b 6c 6d 6e 6f
70: 70 71 72 73 74 75 76 77

As far as I know, this sensor has address 0x5a and I can see this in above output but still not able to understand above output. Can anyone please help me here. Thanks

Answer 1

The most likely problem is a wiring error.

When an i2cdetect probe shows all addresses it suggests SDA is being pulled to ground.

Answer 2

Do you have an Arduino? Then I suggest you connect the MLX90614 to the Arduino and run the I2C scanner code. The I2C scanner code returns the I2C address. Thus, you will be able to verify if your device's I2C address is really 0x5A or anything else.