DMM Shield - Arduino board.

[srss]

Please look at the pictures below. The arduino Mega board is a picture right off the main arduino web site.

The DMM shield picture  is the board we recently purchased.  Clearly the pin out for both boards are not the same.  The arduino mega is listed as compatible on the  DMM shield info on  the Digilent web site. Do we need some type of adapter board that mates with the  Mega and allows the mega to run the DMM shield.??

[kwilber]

The DMM Shield does work with the Mega 2650. Here are two photos showing them mated. I do not have the DMM Shield fully seated so you can see the pins. DMM Shield connector J7 pins 1,3,5,7,9,11,13,15 and J8 pins 1,3,5,7,9,11,13,15 and connector J6 pins 2, 4, 6, 8, 10, 12 do not connect to the Mega.

[kwilber]

If you need access to more of the Mega's pins, you can use stacking headers as shown in this photo.

 

You can also use stacking headers on top of the DMM Shield as I did here when I used a MTDS Shield to mimic a multimeter.

[Bianca]

Hi @srss,

The DMM Shield is compatible with Mega (as is with Uno, Due). All the pins used by DMM shield are connected to the Arduino Mega. As @kwilber said, there are some extra pins that are not mated with Arduino. We loaded those just to have full compatibility with our Chipkit boards that have the extra rows. As you can see in the picture below.

All the signals that the DMM Shield are using are on the outer pins of the connector to assure the compatibility with Arduino. The rest are loaded in case you need to stack other shields on top of the DMM to have access to the chipkit pins.

 

I hope this helps you.

Best regards,

Bianca

[MatthewNevels]

Bianca, I do not yet have  the DMM Shield in hand, but looking at the documentation shows that it is using Arduino I/O Pins 11,12,13 for SPI.  The Arduino Mega/Due do not have SPI on those pins, they only have SPI accessible on the ICSP header and the Mega additionally has it broken out on the I/O header at the end of the board.  The DMM Shield does not connect to either the ICSP or the I/O Header at the end of the Mega/Due.  How are you suggesting that we connect SPI to the DMM Shield?  My only thought is to Set the Mega pins 11,12,13 as Inputs and then to jump the SPI pins on the Mega/Due to 11,12,13.  Please let me know if this is the intended implementation or if there is some other method that you are claiming Mega/Due compatibility as I'm designing a Mega shield which the DMM Shield will connect to and I will need to include that update in my design if that is the intended method of connecting SPI.   

On another note - I have two requests:

1. It is not clear in your documentation what the pinout is due to the additional headers and how they are described as 'top row' and 'bottom row' - is there a way you could add a visual pinout guide similar to the images you get when you search for 'arduino pinout' and just mark out the pins that are connected?  I believe I understand after looking at the schematic, but it would be helpful to others as well.
2. It would be tremendously helpful if a mechanical drawing (or better yet, a 3d model) was available of this board.  This would make it much easier for customers to determine mechanical constraints when working with this product.  

Thanks, I look forward to getting several of these in hand and using them to automate some of our production testing!

[JColvin]

Hi @MatthewNevels,

The SPI material works because the SPI protocol is bit-banged rather than using the hardware SPI and have the bit-banged SPI pins defined in gpio.h as 11, 12, and 13, which is available in Arduino DMM Shield Library on our GitHub: https://github.com/Digilent/Arduino-DMMShield-Library.

With regards to your two requests, I don't have an Arduino pinout available as of yet, but I did adjust the 'top row' and 'bottom row' labeling in the Reference Manual here: https://reference.digilentinc.com/reference/add-ons/dmm-shield/reference-manual#appendixpinout_tables, to inner and outer row to make it less ambiguous. Let me know if there is an alternate phrase that you feel would be better.

I have asked another engineer if we can get a 3D model or mechanical file for the DMM Shield.

Thanks,
JColvin

[MatthewNevels]

JColvin - Thanks for the quick response!  Bitbanging the SPI on these pins in your library makes sense.  That was not clear in the documentation so thanks for clarifying.  Inner and outer rows is definitely more clear in the labeling of pins and is very helpful.  Thanks again for your help, I'm looking forward to getting a few of these DMM Shields ordered - it looks like a great product!

Matthew

[JColvin]

Hi @MatthewNevels,

I have attached a .zip file containing the .step file and the dimensional drawing of the DMM Shield. I will note they are not the fanciest drawings (for example, it doesn't include the pins that are used to load the shield onto the host board), but should have the other relevant dimensions that you would need. Let me know if you need some particular dimensions measured and I can measure those with calipers for you.

Thanks,
JColvin

DMM_Shield.zip

[MatthewNevels]

Thanks @JColvin!  The drawing and STEP have exactly what I was looking for - this will make putting the rest of my mechanical design together much easier!