CmodS6 output varies from one to another

[Lorree]

I am currently teaching (long term sub) PLTW Digital Electronics and we havent really used the cmodS6 very much but are currently working on a project to create a 60 second timer.  I have 45 students and only 8 cmods that we are sharing between 2 classes so they are getting a good workout.  My question is, where is it shown what pins on the cmod are to be assigned to what?  For instance, I recently learned that CLK should only be assigned to PIO14.  Also, I am getting erratic results when I assign my display segments for DIG1 and DIG0 to the lower number pins, but if I assign them to higher number pins such as 15 -21 or 26-32 I no longer get erratic results on my display.  Also, I have a working functioning protoboard that I have wired up and I have been testing each cmod I have and have come across a couple when I plug them into my circuit I may lose a segment or two from my display?  What would cause that?  I havent touched the wires at all just replacing he cmod.  Does that mean some part of the cmod has shorted out?  Thanks so much for the help!

[jpeyron]

Hi @Lorree,

I am unfamiliar with your set up. Could you be more specific with what project you are using to test the Cmod S6.

Could you also include a picture of your testing set up for the Cmod S6's? 

Are you using the USB or VU to power the Cmod S6?

 If you are using the VU what Voltage and amperage are you using? 

thank you,

Jon

[Lorree]

I have attached a picture of my setup.  We are using the Digilent myDigital Protoboards to test the cmods.  We run the digital display using NI myDAQ and the NI Elvis Instrument launcher.  The cmod is powered by a usb as is the NI MyDAQ.  I have posted a picture of the setup with the cmod.  You can see how segment f is not illuminated.  I had just switched out the cmod with the previous one working perfectly, and this one I had missing segments in the display.   It should show 05. I assume this is an issue with the cmod.  I am having this problem with several cmods in my class.  Does this help?  

[Lorree]

The other issue im having with some of the cmods is that if I push straight down on the top of the cmod then some of the segments will illuminate.  I am not sure if this is the protoboard or cmod thats malfunctioning.

[jpeyron]

Hi @Lorree,

Could you use a DDM or o-scope to check the Cmod S6 pins in question.  Do you have another myDigital Protoboard to see if it might be the myDigital Protoboard? If not could you move where you are testing the Cmod S6 on the main bread board part of the myDigital Protoboard? Also could you look at the solder points on the Cmod S6 to see if there appears to be any loose pins.

thank you,

Jon

[Lorree]

This is the multisim file we are using to export to the cmod.  

[JColvin]

Hello @Lorree,

Unfortunately, since none of us here at Digilent have a lot of experience with Multisim, we are not going to be able to provide the proper level of support for your question. Our recommendation (as the same recommendation will likely be with your email conversation with our support team) would be to contact the dedicated PLTW support email, productsupport at pltw.org, where they will be able to provide much better support than we can offer.

Please let me know if you have any questions about this and I apologize for the inconvenience this has been.

Thank you,
JColvin

[Lorree]

OK but its not a multisim problem but a cmod problem in my opinion as I can use multiple differend cmods on the same digilent protoboard setup as you see above with the same wiring set up and get different results.  I am not quite understanding how this is a pltw issue and not a digilent issue with the cmod?

[JColvin]

Hi @Lorree,

It's not necessarily the Cmod S6 as you are able to push on some down on some of the Cmods to create a connection between it and the protoboard, indicating a potential problem with the protoboard. Have you been able to test the Cmod S6 pins with an oscilloscope (or by connecting a LED with the anode touching the Cmod S6 with the cathode connected to ground)? That would help show if there is a proper electrical connection. Another good test to perform would be to physically move the Cmod S6 to a different location on the protoboard and move the wires on the protoboard with it; this is useful to try because breadboards are not always fully reliable long-term.

Additionally, though please do correct me if this is not the case, my understanding is that this hardware setup was procured from PLTW, so they would be more familiar with it than anybody at Digilent.

Thank you,
JColvin