Reading SPI of MAX31855

[Theophrastus]

As raw data I get 0111 1111 1111 1101 0010 0011 0011 0000 - running your VIs.

[Theophrastus]

The datasheet says that the chip assumes a linear relation; the different models just account for the different Seebeck coefficients. That's at least the way I understand the datasheet, but of course I hope that I'm wrong. Maybe it uses several linear functions for different temperature ranges...

On the other hand - if I'm reading it correctly - it states that the maximum error is +/- 6°C.

Tomorrow I'll know for sure, because then I can test it with a type S TC; until now I've used a type K, for comparisons sake.

[Theophrastus]

I run your VIs, and everything is working.

[LeXLuther422]

I edit the lifa firmware in the arduino program. I did edit the LabVIEWInterface.pde so my changes should be in there but I don't know how you do it in lavbiew and get the diff file.

NathanB. wrote:

Samething that I did, essentially, for just the TC data except you failed to include the LIFA firmware.

[Nathan_B.]

LeXLuther422 wrote:

I edit the lifa firmware in the arduino program. I did edit the LabVIEWInterface.pde so my changes should be in there

I see what happened.  You let your Arduino IDE change the extension (which I do not) so when I opened the lvlib those files were "missing".  So, The one thing that I notice is that you send the least significant byte first but then use it as the most significant byte in LabVIEW (the "hi" argument of the "Join Numbers" function).

LeXLuther422 wrote:

I don't know how you do it in lavbiew and get the diff file

To create the .diff file, I use the Linux diff command on my Linux box.  I will start adding them to my custom LIFA firmwares so that people can glance only at what was added/changed.

[Nathan_B.]

Theophrastus wrote:

As raw data I get 0111 1111 1111 1101 0010 0011 0011 0000 - running your VIs.

The first two bytes look fine.  The second two bytes I'm not too sure because if the circuit is open the first bit (on the far right) should be 1.

Theophrastus wrote:

The datasheet says that the chip assumes a linear relation; the different models just account for the different Seebeck coefficients. That's at least the way I understand the datasheet, but of course I hope that I'm wrong. Maybe it uses several linear functions for different temperature ranges...

On the other hand - if I'm reading it correctly - it states that the maximum error is +/- 6°C.

Tomorrow I'll know for sure, because then I can test it with a type S TC; until now I've used a type K, for comparisons sake.

I didn't see that note about non-linearity.  That is unfortunate. 

[tester0070]

I have purchased the Max 31855 board from Ada Fruit and am using it with my Uno and Mega.  The board is described here:

http://www.adafruit.com/products/269

Using the vi above I am getting zero as a reading.  I tried to troubleshoot a bit but figured I would ask a couple questions as well.

1. Do I need to be using the custom LIFA base above, or will the current LIFA base work with this VI?  I did not reload and am using the current base.

2. The ADA Fruit breakout board has a bit different markings than the VI. I assume that DO on the ada board is SO pin in vi, assume that CLK on board is SCK in vi, and assumed that CS was CS both places.

Any inputs to get me up and running here?

Cheers

[LeXLuther422]

yes you do need to load the custom base it has the code needed to talk to the MAX chip and you are correct about the pin assignment.

[tester0070]

Thanks.  So what changes were made in this base file?  I am using the current base file in the project.  If I re flash to this should I expect other issues to show up due to the base file change?

[LeXLuther422]

added cases for the max chip and this vi. Unfortunatly my laptop that had everything on has crashed and I lost all my files. so I can't go thru them and compate but the base file is capable of being opened and edited with the arduino editor there will be 2 sections that say MAX31855 you might be able those to sections over to the newest base and get it working.