Alternate Duet Display and Touchscreen Project

I have a duet wifi controlling my printer, and I made a display screen to do some basic functions. It's not better than the PanelDue, just simpler.

I use the web interface for most things but wanted to be able to pre-heat, pause and resume, and see the general status at the machine.
It uses a Nextion display with an Adafruit Feather M0 board to communicate from the Duet to the display.

Here is a link to the project: [www.holdentechnology.com]
More details at the code repo: [github.com]

Let me know if you make one!

I came across this project while looking for information on using the 'panel due' connector for another purpose. I've seen the website and the Github pages too.

There's something that concerns me about it though: Connecting the panel due Rx pin to the Arduino Tx pin is my worry.

The Duet works at 3.3v and the Arduino outputs 5v on its pins. Shouldn't there be a two-resistor divider between the two?

It seems dangerous to just connect them directly, because even if it works, it's exceeding the maximum rating and is likely to fail eventually.

I've got no problem with the Duet Tx into the Arduino Rx, as the Arduino (only just) accepts 3.3v as a 'high' level, and there's no stress involved.

Quote
woodscooter
The Duet works at 3.3v and the Arduino outputs 5v on its pins. Shouldn't there be a two-resistor divider between the two?

Yes definitely, if it is a 5V Arduino.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Thanks for that confirmation, dc42.

Your response has made me go back and check my assumption that breezetrees design was interfacing with a standard Arduino.

In fact, it uses the Adafruit Feather M0, which is fully 3.3v. I kind of assumed it was a 5v interface. Sorry, my bad.

This design sends G-code to the Duet2 using the panel due port. Checksums are disabled with this application, using M575.

Can you tell me where I can find a spec for sending a checksum with each line? In my application I would prefer the error detection that checksum provides.

Breezetrees doesn't send line numbers with the G-code? Is that OK?

See [reprap.org] for the checksum calculation. It's very crude and doesn't protect all that well. Using checksums requires using line numbers too.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].