Can I be using the Arduino Yun for Shield with Arduino DUE?

I have read that the Due and Bridge will work with the (now obsolete) Yun Shield or Dragino, et al. I have numerous versions of the YUN, Rev0, the .org board and Rev2. However the DUE has many features I desire to use for more complex sketches in the same eco-system as the YUN where I have many already on my local network. It seems that if one ties the 32u4 reset to ground on the YUN, which apparently tri-states all data pins on the 32u4 I should be able to use the LINUX part of the card connected just like the shield to the DUE. Has anyone got a clue if this is practical? I don't think I would mesh all of the pins on the cards together, but rather just use ground and the UART pins, D0 & D1. I do understand that the DUE USB port must be used for programming. Comments and/or experience much appreciated.

I can't speak about the compatibility of the Bridge library with the Due's SAM processor. But that doesn't seem to be your question.

You want to disable the '32U4 so that you can connect D0 and D1 from the Yun to the Due using some jumper wires, so that the Due can talk to the Linux processor. While I haven't tried it, I can't think of any reason why this shouldn't work (assuming that the Bridge library works on the Due, which doesn't seem to be a concern of yours.)

I don't think it's necessary to hold the '32U4 in reset. I think it would be easier to load a sketch into the '32U4 that sets D0 and D1 as inputs, and does NOT call Serial1.begin() or Bridge.begin(). That should accomplish the same thing as holding the '32U4 in reset, and still allow using it for other things, if desired. It won't be able to use D0, D1, Serial1, or the Bridge library, but all of the other pins should be fair game.

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Hello Shapeshifter. Well actually The Bridge library is of interest, since I'll want to use the SD card too, as part of the whole scheme. Hadn't thought about the sketch in the 32u4 to D0, D1 but that is doable, of course. The 3.3 V Due isn't an issue but I have to see if a level shifter is needed interfacing to the DUE. And I still have to track down whether the SPI is also essential as it used in the Dragino application. (also no longer made). Thank you for the response, BTW. I know you are tuned into the YUN better than most on the Forum. I appreciate that.

I hadn't considered level shifting, that will probably be necessary as the D0/D1 pins are 5 volt logic. It's ironic that the Linux side is 3.3V logic, and there are already level shifters in place to translate from the D0/D1 pins to the Linux processor. It would be nice if shifting from 3.3 to 5 back to 3.3 wasn't necessary, but that would require trying to solder fly wires onto tiny pins, which can tend to be finicky and fragile. If that were done, it would probably be necessary to disable the existing level shifter on the board, which I believe can be done by controlling a GPIO line on the Linux side (the proper pin can be determined by looking at the schematic, which I don't have in front of me at the moment.)

The SPI interface shouldn't be necessary for proper functioning of the hardware or the Bridge library. As far as I know, it's only used to load a new sketch into the '32U4 processor using the Linux system (either from the web interface, network socket, or Linux command line.) For example, if you choose the Yun's network address from the Arduino IDE's Port menu, when you upload a new sketch the firmware image gets sent to the Linux processor, which then loads the image into the '32U4 using the SPI interface, just as if you were using an ISP programmer pod.

If you wanted to use the SPI interface in your project to communicate between Linux and the Due, I'm sure you could hook them up, but I wouldn't count on being able to load software over it: the command line tools on the Linux side to do so assumes a '32U4 processor, and would take some changes to be able to load code on the Due.

All great observations. Haven't gotten to the chore yet, with holiday wrappings taking priority on the buss. I might also look at the MKR ETH and MKR ZERO but I'll need to find a way to host a web page on the board if I can. This was cool:
Nice part of the YUN (and maybe the shields) like this:
GitHub - SapientHetero/Ethernet: Ethernet Library for Arduino
The Yun can run PHP as it handles all my data display just fine. Happy Holiday.

This enthusiast "drmpf" seems to have a solution that could apply in the Yun case. Making a record here for the future and for others. The sketches are a great starting point for this NOOB.

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