MAX31855 component: fails to return temperature and faults "7"

I would second the GND suggestion, and since the 7I80HD has a GND per signal
I would use as many GNDs as signals to reduce GND bumping.

 

i happened to think to use halscope to view what LinuxCNC is receiving from the MAX31855 board. the data changes with each scope cycle, suggesting it is outputting data, but also dumping the data from a (possible incorrect) fault code. maybe due to my cheap boards.

ground signal tested out fine, though i still have only one wire from the board to ground. i will upgrade if i can't figure out why it is receiving data and dumping it in the trash.

i have the 7i80HD-25 Pullups set to on, at 5V... what are the chances that when the machine is not running that the unprotected data pin is getting fried by the pullup? i checked the schematic, and the data pin of the max31855 board does not have protection from 5v like the CS and CLK pins do. i think tomorrow i will disable the pullups and try a new, unmolested MAX31855 board, just to rule it out. other than my stepper driver signals, the I/O is most all run through a SSerial board, so i don't think disabling the pullups will harm anything.

 
the schematic from adafruit

According to your halscope plot, Its outputing data so that does not
seem like the output has been damaged (its probably clamped to
diode drop above 3.3V by the MAX38155)

Also the halscope plot shows the same repeated data
(if the halscope display was adjusted, you could read the actual data)

Its also a bit odd that inverted data is used. Have you tried
non-inverted data?

Hi travis036,
I have the same problem with max31855 as you have described. Did you figure out what was wrong with your setup?
My hardware is: mesa 5i24, custom bit file (4 step motors, 2 encoders for spindle and spindle cooling test, modified wj200 vfd driver to support Omron MX2/1kHz vfd, ATC, ect... still under construction)
BTW
This is my first post here, so hello to every one.