The SKR Mini E3 is an affordable, 32 bit board upgrade for the Ender-3 and Ender-5 3D Printers. The form factor (shape) and layout are an exact match to the original Creality boards, making it a simple drop-in replacement.
It comes with a blazing fast 32 bit ARM Cortex processor, the latest TMC 2209 silent stepper drivers for ultra quiet performance and pre-loaded with Marlin 2.0 firmware. No need to flash a bootloader or tinker with settings, just hook it up, turn it on and start 3D Printing.
SKR Mini E3 vs Creality Board
Creality 3D Printers like the Ender-3 are shipped with a basic 8-bit Melzi board, integrated A4988 stepper drivers and 128 Kb flash memory. That’s more than enough to get us started, and works just fine out of the box, but this is ancient hardware that is starting to show its age.
32 bit boards on the other hand have been available for years, but few people could justify the hefty $150+ price tag. That is where the budget family of SKR boards from BigTreeTech, specifically the SKR Mini E3, changed the industry over night.
These are now less expensive than the old 8-bit options, have more than 5x the processing speed, and at least twice the flash memory. That means we can enable more firmware features like auto bed leveling, linear advance and full color graphical displays.
8-bit vs 32-bit Processors
When we’re 3D Printing, constant commands from the G-Code file are sent to the board, telling it to move the nozzle from the current point A to the next point B. A basic 8-bit Melzi board with 16Mhz can handle straight lines (ex: cube) just fine, but more complex curve operations (ex: cylinder) require extra processing to figure out.
This can severely bottleneck performance on organic shapes, especially at faster print speeds, and ultimately creates visible artifacts and degradation in the object.
32-bit boards on the other hand, like the SKR Mini E3 with a 72Mhz chip, can handle these advanced calculations without a hitch. That means faster printing and better results, because the processor isn’t throttled while trying to figure out the next move.
A4988 vs TMC2209 Drivers
Stepper drivers are small chips that control how the stepper motors operate, sending electrical pulses that turn it to a certain degree. Because a half-step and full-step rotation is too large for the precision we need in 3D Printing, we use micro-stepping to make smaller rotations instead.
The generic A4988 drivers included on Creality boards are capable of up to 1/16th micro-stepping, meaning a full motor rotation can be segmented out in to 16 steps. In contrast, the latest TMC2209 drivers used on the SKR Mini E3 are capable of a whole 1/256 microsteps.
Unfortunately, due to factors outside of our control, the print resolution only gets a minimal improvement from this at best. However, when combined with other integrated features like StealthChop2, it does significantly help reduce the noise output of the motors during operation.
SKR Mini E3 Features
The massive hardware upgrades alone are more than enough to justify the price, but the SKR Mini E3 also comes with plenty of extra features. From auto bed leveling to 32-bit LCD color screens, it can save us time and money with further add-ons down the road.
Servo and Probe ports are integrated on the board for native BLTouch support. No need to purchase an extra Pin 27 breakout board.
Individually addressable LEDs (each light color can be changed) from AdaFruit can be plugged in to and controlled from the board.
Flash new firmware updates direct from the SD card. Just upload the .bin file and on first boot, the firmware is automatically installed.
32 Bit TFT Screen
Replace that blue 80's style display with a modernized 32 bit TFT color touchscreen. Supports serial and 12864 screen ports.
Start by removing the electronics case cover using an M4 hex wrench. There are (3) bolts holding it in place, two in the front and one in the rear. Lift the cover off and place it in front of the machine, or better yet, just unplug the case fan from the board.
Now that we have access, we can start unplugging the various white JST connectors. 5-pin plugs are for the stepper motors, 2-pin plugs are for endstops, fans and thermistors. Most of these are labeled and easy to recognize, but I would suggest marking the rest. Wrap a piece of tape loosely around the wiring and write the plug’s name as shown on the board.
The (4) sets of power cables are different, using a clamping style terminal block to hold the wires in place. Take a flat head screwdriver and loosen the set screws on top, then pull the bare wire ends out of the housing.
Once all of the electrical connections have been removed, we can go ahead and unscrew the board from the case. There are (4) M3 bolts holding it in place, and once they are removed, just take it out and set it aside.
Before we install the new SKR Mini E3 board, there are a couple things to take care of first.
There are (4) blue aluminum heatsinks packaged separately in the box. Peel off the adhesive backing sticker and press fit these atop each of the stepper motor drivers. TMC drivers tend to run a bit more hot, where heatsinks help to dissipate the heat and prevents hardware failure.
It’s also a good idea to check the terminal blocks, making sure that they are opened. With limited space to work once the board is in the electronics case, it helps having them ready to go.
At this point, it’s just a matter of installing the new SKR Mini E3 board and wiring it back up.
Before mounting it in the case, I would suggest plugging in the female XT60 power cables first. Because the terminal block is on the back side of the board, it can be a bit difficult to access otherwise. With these wires already inserted, we can just feed the plug through the rear opening in back of the case.
For the remaining wire terminal blocks, insert the cables and clamp them in place with the set screws. You can refer to the wiring diagram as needed, or do the following from left to right…
The only point to be wary is the fan plugs, which are reversed between the original Creality board and the SKR Mini E3.
If these aren’t swapped during the installation, the hotend cooling fan will always be turned on and have no PWM control. As such, FAN0 should have the yellow/blue wires for the hotend cooling fan, and FAN1 should be the red/black case fan wires.
That’s it for the installation and all it takes to upgrade the board. Once everything is plugged in, go ahead and power on the 3D Printer to make sure it works as expected.
The SKR Mini E3 comes pre-loaded with Marlin 2.0 firmware on the SD card. This is an example build, configured for the Creality Ender 3 with most of the standard features enabled. It’s a convenient way to test our board and make sure it works, but the firmware is often an older version and should be updated when possible.
BIGTREETECH publishes the latest version of this firmware on their Github page, pre-compiled and ready to use. If you don’t need to make any changes, this is the easiest method.
Flashing the Firmware
There are 3 versions of the Marlin firmware available on Github. For users with a BLTouch auto bed leveling sensor installed, use the one labeled as such. Otherwise, firmware.bin file is intended for the standard Z-endstop switch on stock Ender 3 3D Printers.
- Download the firmware.bin file to your computer.
- Copy the firmware.bin file to your SD card (rename the file if necessary)
- Load the SD card in the 3D Printer and turn it on.
Once the 3D Printer has booted up, the screen should stay blue for 15-20 seconds. During this time, the Marlin firmware is being flashed to the board from our file. After it has completed, the screen should load in to the normal interface, signifying that it’s ready to use.