How to build the custom display board

This tutorial will guide you...

through the process of building your custom TWI / I2C display/encoder board.

This custom display / encoder board is sufficient for controlling the SMuFF and showing all information, since it has the same resolution (128 x 64 pixels) as the RepRap Full Grapics display though it is way smaller and doesn't need as much signals.

Follow these simple instructions to get your custom display/encoder board built and running.

Please notice: You don't necessarily have go this way and solder the DIY display board, if that's not your thing. You could also use Dupont wires/connectors to join controller board, I2C display, encoder and buzzer. The I2C display usually comes with a pin header soldered to it and buzzer and encoder are also available as separate modules which are meant to be used with breadboards. Wiring up a decent Dupont cable is much less stressful. The result will be not as compact as the PCB but it'll work the same way.

SKR mini LCD board.pdf
SKR mini E3 LCD board.pdf

The schematic...

for the SKR mini V1.1 is the first one on the left, for the SKR mini E3 / E3-DIP is the second one.

Please notice:
On Rev. 2 an additional NPN transistor and resistor are needed to drive the buzzer!

To build such board, you'll need just a couple of items:

  • a 60 x 40 mm prototype PCB

  • a 0.96" I2C / TWI OLED (typically SSD1306)

  • an rotary encoder

  • a piezo buzzer

  • two 10 K resistors

  • an NPN transistor (i.e. BC547)

  • a 1 K resistor

  • a 5 x 2 header

  • a micro switch (optional, for RESET)

  • a couple of wires

  • a 10 wire flat ribbon cable and two 5 x 2 female connectors

Attention:

You'll need a different layout for the SKR mini E3 (DIP) boards because of the different pin assignment of the board, as shown in the 2nd schematic on the left.

The newly added transistor between signal and buzzer will prevent drawing too much current on that pin from the buzzer.

Signals (pins) used

This display/encoder board uses the display connectors EXP1 from the SKR Mini V1.1 (E3 V1.2 / E3DIP V1.1) controller board, which is usually being used as the connection point for a RepRap Full Graphics display.

Notice: The NEOPX signal, shown in the picture on the left, is optional and isn't being used yet. Also, the Reset button needs to be connected using a separate wire attached to the RESET pin of EXP2 on a SKR mini V1.1 but not on the SKR mini E3 (DIP).

PCB Bottom
PCB Top

Step 1:

Solder all of the pins of the 5 x 2 header to the prototype PCB at the shown position.

Notice: When the board is finished, this header fill face downwards.

Step 2:

Solder the piezo buzzer at the show position onto the PCB.

Notice: When the board is finished, the buzzer fill face downwards.

Step 3:

Wire up the buzzer.

Bring the blank wire (GND) across the PCB as shown, since you'll need that power signal for the other components as well.

REV. 2!

Solder the + signal of the buzzer to +5V. Wire the GND pin of the buzzer to the collector (pin 1) of the transistor. The emitter of the transistor (pin 3) goes to GND. The base of the transistor (middle pin) goes to the 1K resistor and the resistor goes to the buzzer pin on the connector (pin 10).

Step 4:

Solder the LCD at the shown position on top of the PCB. Use the coordinates etched on the PCB for orientation (in this case E-10).

Then solder the 2nd pin to the GND wire on the bottom of the PCB using a solder bridge.

Step 5:

Solder all of the other components to the PCB at the shown positions. Put a solder bridge between one pair of the resistor pins as shown in the lower picture.

Step 6:

Wire the encoder as shown to GND using a blank wire.

Step 7:

Wire up the remaining connections using a wrap wire or any other isolated wire according to the schematic.


Step 8:

Check every single connection before powering up the display board. Be especially careful with the +5V (VCC) and GND signals. If you mix those up or shorten them, you may damage your OLED, your SKR mini or, in worst case, both of them.

The picture below shows you the encoder wiring in detail. Some users have had problems connecting it correctly and thus it didn't work as expected.

Step 9:

Attach the display board to EXP1 of your SKR mini V1.1 controller using the 10 wire flat ribbon cable and power it up.

Step 10:

Check everything is working by turning the encoder wheel.

Notice: Turning the encoder wheel to the left is supposed to show you the Main Menu, whereas a turning it to the right will show the Tools Selection Menu.
If yours is the other way around, this means you've swapped the encoders A and B signal pins (but it'll work anyways).

Final Step:

Make the cable. You need a 80-120 mm 10 pin flat ribbon cable and two 5x2 connectors.

Make sure the index of each of the 5x2 connectors is in the same position as shown in the picture.