I recently purchased v12 of the Sparkfun MLX90640 55° FOV sensor through Digikey. I found that the device was unable to communicate with a Raspberry Pi: running i2cdetect returned that all I2C addresses were taken, not just 0x33 I would expect. Upon further inspection of the module itself, the SDA and GND pins buzz continuity with a DMM. I am using the board with the following modifications: I have soldered a 4-pin 100 mil header for mounting to a breadboard, and I have cut the I2C pull-up resistors.
I appreciate any help you can provide in resolving this issue quickly. I am looking to test this unit so I can make a go/no-go determination in buying over a dozen more to support a robotics competition.
Source of module:
https://www.digikey.com/products/en?keywords=SEN-14844
Hi Scott.
Are you using any pullup resistors anywhere else on your I2C bus and are there other I2C devices on the same bus?
I have tried three configurations:
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As delivered, I soldered the 100 mil headers onto the unit and attempted to communicate with it using the Raspberry Pi. At that time, I noticed the i2cdetect reported devices on all addresses, not just 0x33 I would expect.
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I removed the unit from the setup, cut the pull-up traces on the unit, then returned it to the setup connected to the Raspberry Pi. The i2cdetect command continued to report devices on all addresses, not just 0x33, so cutting the traces appears to have had no effect.
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I researched online and found reports that this unit has been known to have fabrication errors (ref links below). I removed the unit from my setup and performed an electrical checkout and found the SDA and GND pins were tied together. Regardless of my test setup, the unit itself exhibits unexpected behavior on its own. At this point I am operating on the assumption that the unit I have is defective. I am concerned about the implications of that because I purchased this unit to develop code against before buying many more for a robotics competition I’m hosting. My hope is that DigiKey is carrying old (defective) stock and that buying future units direct from Sparkfun would give me access to the revised design that addresses this fabrication error (“This is a small hardware issue that we currently have a fix on order for” - Nov2018). However, this is my personal speculation and I would appreciate some verification of my assumptions.
Related fabrication defect reports for this unit:
https://github.com/sparkfun/Qwiic_IR_Ar … 0/issues/3
https://github.com/sparkfun/Qwiic_IR_Ar … 0/issues/1
I may have mis-filed this report (under “IR ranging sensors” rather than “IR imaging”). There is a related report in the appropriate forum here:
https://forum.sparkfun.com/viewtopic.php?f=151&t=49734
Is the path forward to request a replacement as was done in that thread?
Hello Scott.
It looks like you have the most current version and something is obviously wrong with your board. I apologize for that.
If you contact Digi-Key, they will be happy to replace this for you.
