Marlin and OctoPrint sharing the same display
May 24, 2022 01:30PM
I'm developping a "thing" that allows the Marlin and OctoPrint user to share the same display for OctoPrint and Marlin. Unfortunately, the Raspberry Pi has no slave mode (why ??????), and Marlin acts as a master when communicating whith a display (RepRapDiscount Full Graphic Smart Controller, etc.).
As a workaround, I created a shield that is seen as a slave by Marlin, and as a slave by the RasPi.


A STM32 catches Marlin UI frames, converts them into a bitmap, and sends a signal to the Pi. Then, the Pi reads this bitmap and displays it.

The OctoPrint plugin installs a low level "driver" that directly writes to the RasPi VRAM, creating an overlay window showing Marlin UI.
This overlay window is customizable from a OctoPrint plugin (size, colors, transparency).
There's a demo mode that does not require the custom hat (no electronics needed) : just a button between a GPIO pin and GND.

The custom Pi hat is a huge limitation because very few people (if any) will make a PCB and populate it !

I'm now thinking of something else. Marlin uses a custom u8glib library. So I'm thinking of an additionnal u8glib mode that would act as a SPI slave, and give its bitmaps to the RasPi, without the need of any electronics.

But is this doable ? Could Marlin communicate over SPI asynchroneously ? I fear some timing issues !

Is there some Marlin devs on ?
Where could I communicate ? (of course not on Marlin Git, it is for issues and FQs, not for development)
Maybe Discord, but I'm unable to speek english fluently : not an option

Edited 1 time(s). Last edit at 05/24/2022 01:32PM by yet-another-average-joe.
Re: Marlin and OctoPrint sharing the same display
June 27, 2022 06:27AM
This display works with marlin firmware run on pi(pandapi) and so it can display and control the gcode file in the octopi.
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