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Topic: Melexis SMBus IR Thermometer - NFI (Read 39650 times) previous topic - next topic


I've tried EVERY bit of code I can find and I can't get squeak out of this sensor!
When I try the i2cmaster library, I can't get any output on the serial monitor.
I'm now trying the code sensorJunky posted and still no output on the serial monitor.
I'm going to have to get the CRO home!
I think I've been spoilt by the other I2C devices I've tried, HMC6352, eeproms, my uM FPU!


cyberteque, did you see the notes about pull-up resistors in the older posts on this thread?  

This device is SMBus protocol, not I2C so that is one reason, I assume, that many are having trouble.

I am a beginner so be careful with my advice ; )  but one thing I have recently found is here:


maybe it will help.  I still like the idea of setting up this device to output PWM instead of communicating on the SMBus.. however I will have to first figure out how to make it do that.


I tried the 4.7K pull up resistors, but that didn't work.
There is another document on the Melexis site, I'll post the address later, it has "preliminary" stamped all over it, but it does look hopeful.
I'm going to have another go at it when I get my Tektronics storage CRO home, I think I'll have more luck.

On thing to bare in mind is SparkFun has an evaluation board for the MLX90614


If you have a look at the schematic


They have just hooked the sensor up to the I2C port, no pull ups!

Unfortunately the link on github is broken, so I've not been able to download their source.

Has anyone found out why using the i2cmaster library prevents the UART working?
As a few people have pointed out, even a simple "Hello World" no longer works on the serial monitor!

The PWM output is going to be a "chicken and egg" problem, you'll have to make it work over I2C to set it up!

As I'm going to use this sensor in my "tricorder" thing, I was going to mount it in a "wand", along with some gas sensors.
My idea is to use a separate ATMEGA in the wand and communicate back to the main unit via serial link.

I already have 10 devices on my I2C bus, an HMC6352 digital compass, a DS1307 RTC and 8 24LC256 EEPROMS, I'll also have a temperature and humidity sensor when it arrives, that'll make 11, 12 if I put my uM-FPU V3 on the I2C bus, but I think I'll keep that on the SPI bus along with my MPL115A.

From what I've read SMB and I2C devices are going to be "difficult" to have on the same bus.
So a dedicated controller in the "wand" seems like a good idea.
I've already ordered a few ATmega328's pre-programmed with the Arduino bootloader, I've found the keypad library a bit "twitchy" when you have a lot of stuff going on.
So I was going give my keypad it's own controller to scan the keys, make the key press "beep" and do some other stuff.

This project is taking on a life of it's own!
I'll have to start documenting it now it has the beginnings of a case.
And before you ask, yes, my Mega still has a few port pins I'm not using, yet.


oh!  I probably should have purchased the sparkfun board.  thinking back... i probably did not do that because it runs at 3.3V and I wanted to run at 5V and because I wanted the 10degree field of view.  It could be that this board works due to running at the lower voltage... it might be more compatible with SMBus at that level.

I purchased the Parallax board with this sensor but I have not actually tried it yet.  One thought I had is to find another development board that could do SMBus native and use that to set it to PWM output... but in order to try that I may have to purchase a bare sensor.

here's one more off the wall thought.. sparkfun has this temp gun.


and it appears to use this sensor inside it.  A person could buy this and then hack it.

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