Prusa Instructions Connect Raspberry Pi GPIO Directly to Ground?!
If you follow the Prusa directions to setup OctoPrint with a Raspberry Pi Zero W:
https://manual.prusa3d.com/c/Octoprint_for_Original_Prusa_i3_MK3
Prusa has you solder 6 pins to the Raspberry Pi that plug into the J19 header of the Einsy Rambo board. Only the four consecutive pins appear to serve any electrical purpose (5V Power, Ground, TXD, RXD). The other two GPIO pins are not configured in the instructions and I am guessing they were only added to increase the mechanical rigidity of the mount. One of them is connected indirectly to the reset pin of the ATmega2560 chip (pin 13 of the J19 header). The other GPIO pin is connected directly to ground (pin 14 of the J19 header).
What is the problem with connecting a GPIO pin directly to ground? If that pin is ever configured for output and set high it will create a short circuit that could destroy the Raspberry Pi.
More information:
Einsy Rambo Schematic
https://elinux.org/RPi_Tutorial_EGHS:GPIO_Protection_Circuits
RE: Prusa Instructions Connect Raspberry Pi GPIO Directly to Ground?!
This text is copied from the Octoprint.org download page:
Recommended hardware: Raspberry Pi 3B.
Please note that the Raspberry Pi Zero W is not recommended since severe performance issues were observed, caused by the WiFi interface when bandwidth is utilized (e.g. the webcam is streamed), negatively impacting printing results. See also here.
RE: Prusa Instructions Connect Raspberry Pi GPIO Directly to Ground?!
What is the problem with connecting a GPIO pin directly to ground? If that pin is ever configured for output and set high it will create a short circuit that could destroy the Raspberry Pi.
Usually only the GPIO chip is being fried or one port. Rpi would still work fine.
It looks to me like only couple pins exist on the RPi Zero which is supplied by PR. Maybe someone who purchased this setup can confirm.
Often linked posts:
Going small with MMU2
Real Multi Material
My prints on Instagram
RE: Prusa Instructions Connect Raspberry Pi GPIO Directly to Ground?!
https://d17kynu4zpq5hy.cloudfront.net/igi/prusa3d/E1U3vFAEsJpAIPrs.large
shows you are only to install6 pins in the pi-zero which avoid the problem
RE: Prusa Instructions Connect Raspberry Pi GPIO Directly to Ground?!
@robert-rmm200
Not everyone is streaming video on their OctoPrint server. People are using the same directions to connect Raspberry Pi 3's (via jumper cables) and Banana Boards (Zero footprint w/ 4 cores) to the Einsy Rambo J19 header. Raspberry Pi Zero W works fine with OctoPrint if you don't stress the CPU while it is printing. OctoPrint is a horribly bloated project that prioritizes features over performance and clean code. It is possible to connect ethernet to a Pi Zero or Pi Zero W to improve streaming performance.
@nikolai-r
@david-a66
Maybe some pictures will make the issue more clear. The image below shows the six pins that are connected between the Einsy Rambo J19 header and Raspberry Pi 3 (same header as Raspberry Pi Zero W). The yellow connection (Einsy Rambo J19 header pin 14 and Raspberry Pi GPIO23) is the problem:
From the Einsy Rambo schematic you can see pin 14 of the J19 header connects directly to ground:
The Raspberry Pi website has this to say about connecting a GPIO pin directly to ground:
https://www.raspberrypi.org/documentation/hardware/raspberrypi/gpio/gpio_pads_control.md
"If the pad is shorted to ground, it will not be able to drive high. It will actually try to deliver as much current as it can, and the current is only limited by the internal resistance.
If the pad is driven high and it is shorted to ground, in due time it will fail. The same holds true if you connect it to 3V3 and drive it low."
RE: Prusa Instructions Connect Raspberry Pi GPIO Directly to Ground?!
Hi
If I correctly understand I can connect my RasPI 3+ to Prusa in the same way of I connect a Pi Zero? So I think is more stable connection than a USB connection (no reset and no problem with streaming).