How to Use ST-Link to Load OpenBLT for Anet ET4 or ET5 3D Printers

The Anet ET4 or ET5 3D printer has a proprietary bootloader built in the mainboard which can’t load Marlin firmware, so we need an additional bootloader tool to run Marlin 2.0 firmware build on them.

What is a Bootloader?

A bootloader is a piece of software that automatically loads the regular firmware in only one or two seconds every time when you power on the printer or hit the reset button.

When we turn on the printer, the mainboard looks for it at a specific memory location and starts running it.

To upgrade firmware version of your 3D printer, we need the bootloader to detect new firmware file on the SD card or the connected USB port. 

Determine Procedures to Load Firmware File into the Printer

Usually, there are three different kinds of bootloaders prebuilt in a 3D printer.

  1. Some manufacturers developed their own bootloader for the printer which allows firmware updating. To update firmware version, we only need to save an “.ini” firmware file with a new name into an SD card and insert the card into the printer, and power on the printer. It will automatically load the new firmware.
  2. On a printer with open BLT bootloader (developed by Feaser), we only need to load a “.srec” firmware file instead.
  3. Some bootloader is not compatible with some firmware version especially the open source Marlin firmware. So we need an extra tool like ST-Link debugger or programmer to flash a new bootloader to run firmware updating.
ST-Link utility
ST-Link utility

    The bootloader of Anet ET4 and ET5 series 3D printers belong to the third kind. That is, to do Marlin 2.0 firmware flash on Anet ET4 or ET5 3D printer, we will need a ST-Link or JLink for the printer.

    Install ST-Link V2 to load OpenBLT on ET4 or ET5 mainboard?

    Step 1 Power off the printer before the J-Link or ST-Link flash

    Step 2 Connect the ST-Link to the main board.

    Three pins include GND, SWCLK (SWC) and SWDIO (SWD) pin should be connected accordingly on the mainboard. The three pins have slightly different names on STlink and Jlink. In ST-Link, the SWDIO, data pin is called IO. The three cables have three colors, on JLink, the GND cable is black, SWCLK cable is yellow, the SWDIO is the blue cable.

    ST-Link and Anet board pin connection

    ST-Link and Anet board pin connection

    Step 3 Run the ST-Link utility on your computer.

    Use the extension cable to connect the ST-Link or Jlink with your computer. Turn on the printer.

    stlink for 3d printer

    Step 4 Click on the plug connector (the third icon on the top) and the ST-Link will connect to target. 

    ST-Link utility

    Current program loaded on the mainboard shows here. Now we need to replace the program with a new one.

    mainboard program loaded on the st link 

    Step 5 Click on the “Target” tab and select the option called “Program”. It will prompt us for a file to load.

    load new program through st link 

    Step 6 Download the “openblt_et4.bin” file. developed by David Teran on GitHub.

    Marlin firmware of Anet ET4 and ET5 downloading

    Marlin firmware of Anet ET4 and ET5 downloading

    Step 7 After downloading the files on Github. Now click on the “openblt_et4.bin” file and click on “open” and then click on “start”, the bootloader will automatically transfer from the computer to the mainboard.

    Marlin firmware files of Anet ET4 and ET5

    Marlin firmware files of Anet ET4 and ET5

    program new firmware on ST-Link Utility

    program new firmware on ST-Link Utility

    Now we’re ready to restart the printer and run Marlin 2.0 build on Anet ET4 or ET5 3D printer. And in the next article, we’ll introduce how to do that. Hope you enjoy your printing with Anet 3D printer.

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