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FordPrefect

Versions of LabView that work with WF32

Question

I have a full suite of LabView already, can I use it instead of the "Home Bundle"?  

Also, will PID VIs work on the WF32?  And can it communicate with I2C based temperature sensors?

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Hi FordPrefect,

Yes, you should be able to use the full LabVIEW suite instead of the Home Bundle, but from what I understand, you would also need NI Linx (referencing your other post) to communicate to the chipKIT WF32. 

As for the PID VIs, I don't know that answer since it seems like you can use a lot of VIs with the WF32, but I don't know what the restrictions are. I'll ask our LabVIEW guy for you and he'll get back to you here on the forum.

Yes, you would be able to have the WF32 talk to I2C temperature sensors and send the resulting temperature (or data stream if you want your PC to do the computation) back to LabVIEW over USB (or WiFi).

Thanks,
JColvin

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I'd like to use a few of your PmodTMP3 sensors and my "LabVIEW Physical Computing Kit with chipKIT WF32 " to log temperatures in my attic via wifi.

Assuming the chipkit provides sensor power, the only additional hardware I need to procure is the cables to daisychain the sensors? Couldn't find i2c cables on digilent.com.

Thanks,

MinerHokieRamp

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Hi MinerHokieRamp,

There are some 4 wire cables on the Digilent website; they just aren't in the Pmod section for some reason. But you can find a 4-pin to 2 2-pins option here and the 4-pin to 4-pin option here.

The chipKIT board will provide power for the sensor, although I do not how far apart you can place the daisy-chained PmodTMP3s or have them from host board before losing too much signal driving strength so they do not work correctly. The cables themselves are 9 inches long and I think the stated operating length via an MTE cable for Pmods is 18 inches, but I don't know that for certain. And I guess I don't know how far apart in your attic you planned to put your Pmods.

Let me know if you have any more questions.

Thanks,
JColvin

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I was thinking of running a cable ~15 feet from the chipkit to the first sensor, then about 10 feet between the remaining sensors in the attic, then outside the garage. Probably a total cable length of about 100 feet.

After seeing your 9 inch cables, I did some research. I2C, even when running very slow, doesn't appear to be a good option for logging data from several distributed sensors.

What are the sensor protocol alternatives for the chipKit?

Thanks.

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Hi MinerHokieRamp,

The temperature sensors that Digilent has are the PmodTMP2, PmodTMP3, and the PmodTC1. Both the PmodTMP2 and 3 use I2C and the PmodTC1 uses SPI to get the measured temperature from an attached thermocouple.

All of these will operate off of the 3.3V CMOS logic used by the microcontroller. The problem that I'm seeing is that depending on the cable that you use there will be some inherent resistance in the cable so you may not be able to detect the appropriate high logic levels on either side of the cable.

Thinking about it though, I know I've seen a project where we used a pair of PmodRJ45's and a 10 foot ethernet cable to connect a set of user I/O (a hand-made controller with buttons on it) to the host microcontroller and that worked without any issues, so maybe you could get some distance out of that. An ethernet cable has 4 designated I/O lines so you could use SPI or I2C (or any other serial protocol that needs 4 or less I/O lines) with it. I don't know how big of a cable you could use though before running into any issues though (but at least it's much longer than a MTE cable distance).

Thanks,
JColvin

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In separate correspondence with TI, TI recommends using UART temperature sensors for long bus runs, up to 300 meters for UART, according to TI.

One of the ladies at the Digilent booth at NI WEEK yesterday was confident that the WF32 has a UART interface. I looked at the WF32 description on this website; no mention of UART, so I think she's wrong.

Regards,

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The WF32 has 2 UART Ports. UART1 is on pins 0 (RX) and 1 (TX) while UART4 is on pins 39 (RX) and 40 (TX). UART1 is also routed to the on-board FTDI chip so it cannot be used alongside the USB-UART bridge. For more information on the UART ports see the UART section of the WF32 reference manual.

 

BKallaher

Edited by BKallaher
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Thanks, Sorry about the specification confusion. I assumed that since UART ports weren't mentioned on the basic I/O list, it didn't have them. I hadn't looked at the detailed specifications you sent.

I'll see about stringing together some TI TMP107 sensors and accessing their outputs via WIFI.

Thanks again,

MinerHokieRamp

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