Research

I was researching that for a bit until i found some hints that this is possible. It all started with the finding of the original firmware  and a hint how to upload it . But then i found an Issue where the discussion went into the right direction: Obtaining the sourcecode  and an instruction how to update this . And finally also a hint how to extend the timeout .

Fortunately, the user sobieh had changed the firmware in his repository  so that the relay doesn’t need a reset but - and that made it unusable for me - he also changed a couple timeouts and the behaviour of the relay was modified so that it is enabled when the pin is pulled low. For regular cases (where the pc managing the printer is running 24/7) this makes sense but for mine (BTT E3EZ Board with a CB1 onboard) it doesn’t.

So i needed to get into assembly which - thanks to ChatGPT was less complicated than i thought.

Custom Firmware Description

So there it is - the firmware for the BIGTREETECH Relay 1.2 with the following features:

• Shutdown Delay of 30 seconds (allows to shutdown a CB1 or CM4 embedded on your mainboard)
• Startup delay of 30 seconds (allows to start towards klipper without triggering a shutdown)
• Checks every 3 seconds for a changed pin (meaning that it can take up to 33 seconds to shutdown your relay)

Custom Firmware implementation

Prerequisites - Hardware

To implement the modified firmware you will need a serial adapter, e.g. a CH340 ( Aliexpress* or Amazon* ) and a Windows Host.

Prerequisites - Software

• Clone the repository from here .
• Obtain & Install Keil C51 Development Tools 
• Add the path to your C51.exe to the Windows PATH variables
• Obtain and Install Python 3 
• Run:

  1	pip install stcgal

Build Firmware

• Change to the cloned git repository
• Run build.bat

Upload Firmware

This instruction is to be used at your own risk. We are not liable for any damage.

• Disconnect any mains voltage
• Connect the relay board to any USB to Serial adapter
• Run upload.bat COM# where # is your COM port number. To find the number, check the Windows Device Manager
• Reset the board with reset button

The BIGTREETECH CB1 uses a custom IO pinout for the pins which consists of PA, PB….PG and a number. To calculate a GPIO Number, you need to use the following formula:

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[(PG - PA)*32] + {Pin Number}
Where PA = 1, PB =2….so PG = 7

So if you want to calculate PG19, then it would be ((7-1)*32) + 19 = 211 = GPIO211. Potentially also this lookup table  might help.

The pins of the 40-pin connector are listed here already - maybe that helps to quickly get the right numbers ;-)

References

• https://github.com/So6Rallye/BTT-Pi/blob/018930134b72f43b6b4b242ffafca145bdffbc87/BIGTREETECH%20Pi%20V1.2%20-%20Board%20Fan%20Pin%20Configuration 

Solution

There are different solutions for this but the following one worked the best for me:

First remove NTP:

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sudo apt remove ntp

and install the systemd-native timesync service:

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sudo apt install systemd-timesyncd

This should automatically install the service and start it. To make sure, you can check that systemd-timesyncd.service is active (running):

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systemctl status systemd-timesyncd

And when using:

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timedatectl status

you should see something like:

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System clock synchronized: yes
              NTP service: active

References

• https://askubuntu.com/a/1373363 

GPIO stands for General-Purpose Input/Output. It refers to the pins on a microcontroller or single-board computer, like the Raspberry Pi, that can be programmed to serve as either inputs or outputs. These pins enable the device to interact with the external world by receiving or transmitting digital signals. Through software programming, developers can configure GPIO pins to read data from sensors (inputs) or send signals to actuators (outputs), facilitating versatile applications like the control of fans, lights or other 3D printing accessories.

Thankfully the pinout is the same on the Manta M4P which is why i was able to extract the data from there  (page 9):

BIGTREETECH describes the pinout of the CM4 the same as the one of the Raspberry pi. However when being used with the CB1, the Pinout Changes. I extracted that information and then used various sources of research to find the corresponding GPIO port: This is the final result:

Update: Now i finally found a mapping in the CB1 repo - check there  if you want to see the mapping for the BTT PI or CB1 MMC version.

• EBB36/42 v1.0 uses STM32F072C8T6
  • All Pins but PA0-7, PB0-1, PC0-5, PC13-15 are 5V tolerant
• EBB36/42 v1.1 and v1.2 use STM32G0B1CBT6
  • All Pins but PA4 and PA5 are 5V tolerant

As usual, crosscheck these values, I’m not responsible for any damage resulting out of this article.

References

• https://www.st.com/en/microcontrollers-microprocessors/stm32f072c8.html 
• https://www.st.com/resource/en/datasheet/stm32g0b1cc.pdf 
• https://github.com/bigtreetech/EBB 

References

• Board schematics of the Manta E3EZ 

On different sites i then found the type of connector (Molex Microfit 3.0 2x2 connector) which is supposed to be connected as follows:

I finally found it here  on github:

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_____________________
| B2 | B1 | A1 | A2 |
|_   ___________   _|

Or more visually (please crosscheck the colors with your extruder of choice!)