I am working on a project with an RPi 5, extender to a breadboard, an i2c MLX90614 temp sensor, and an i2c ADS1015 a/d (on an Adafruit 1083 board).
I first added the ADS1015. With the RPi 5 it is detected with "i2cdetect -y 1" at address 0x48 as expected. And my little bit of Python can read a/d from it. No problems.
Then I added the MLX90614. I was unable to detect it with "i2cdetect -y 1" (it should be at 0x5A) but I could not detect it. The ADS1015 was still working fine. A couple of hours spent triple checking wiring, trying a different MLX90614, removing the ADS1015 - could not detect it at all.
There was mention of different i2c timing in some thread: https://github.com/raspberrypi/bookworm ... issues/263
So I switched to a RPi 4. I moved my uSD card from the 5 to the 4 so the software was exactly the same. And immediately "i2c detect -y 1" started finding my MLX90614, and with the ADS1015 back in the circuit i2cdetect could find both i2c devices.
My snippet of Python could read the temps from the MLX90614 - yay!
For fun, I put the RPI 5 back in the sytem. Still could not detect the MLX90614 with "i2cdetect -y 1" but the ADS1015 was detected. On a hunch I ran my Python snippet and could read temps from the MLX90614 no problem. So that was weird: could not "detect" it but it worked. A little more reading, and I figured out "i2cdetect -y -q 1" (q for quick) could detect both i2c devices. Which is weird because the MLX90614 documentation says the MLX90614 cannot do "QUICK" commands. Yet it seems to.
TL;DR
RPi 5 cannot detect an i2c MLX90614 in the usual way "i2cdetect -y 1", but can read temperatures from it just fine in normal operation. The MLX90614 can be detected with "i2c -y -q 1" which shouldn't work but it does.
I don't know if the MLX90614 is not meeting the i2c specification, or maybe the RPi? But the MLX90614 works now so I am happy with that.
Then I added the MLX90614. I was unable to detect it with "i2cdetect -y 1" (it should be at 0x5A) but I could not detect it. The ADS1015 was still working fine. A couple of hours spent triple checking wiring, trying a different MLX90614, removing the ADS1015 - could not detect it at all.
There was mention of different i2c timing in some thread: https://github.com/raspberrypi/bookworm ... issues/263
So I switched to a RPi 4. I moved my uSD card from the 5 to the 4 so the software was exactly the same. And immediately "i2c detect -y 1" started finding my MLX90614, and with the ADS1015 back in the circuit i2cdetect could find both i2c devices.
My snippet of Python could read the temps from the MLX90614 - yay!
For fun, I put the RPI 5 back in the sytem. Still could not detect the MLX90614 with "i2cdetect -y 1" but the ADS1015 was detected. On a hunch I ran my Python snippet and could read temps from the MLX90614 no problem. So that was weird: could not "detect" it but it worked. A little more reading, and I figured out "i2cdetect -y -q 1" (q for quick) could detect both i2c devices. Which is weird because the MLX90614 documentation says the MLX90614 cannot do "QUICK" commands. Yet it seems to.
TL;DR
RPi 5 cannot detect an i2c MLX90614 in the usual way "i2cdetect -y 1", but can read temperatures from it just fine in normal operation. The MLX90614 can be detected with "i2c -y -q 1" which shouldn't work but it does.
I don't know if the MLX90614 is not meeting the i2c specification, or maybe the RPi? But the MLX90614 works now so I am happy with that.
Statistics: Posted by fdunlop — Tue May 13, 2025 2:26 am