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Buile Guide - Electronics

To keep oriented during througout this guide, here is a photo of everything put together without the case.

aball minimal implementation

Electronics

Electronics Arrangement There are only the two main components and they are connected with just six wires in two groups. There are two wires for power, and four which carry the SPI interface lines.

Note the orientation of the MCU and sensor here. The wires are coming out the BACK of the MCU, and go into the sensor side of the breakout board.

I suggest connecting your MCU and flashing it with the firmware before you start assembly. This will let you know that it's functional before you spend time soldering.

Microcontroller

Any pro-micro compatible will work, in this build I'm using an Elite-C as it has a nice robust USB-C connector. If you do choose something else, you'll need to work out some way to reset the unit. The Elite-C has an onboard reset button and the cases here have access holes in the proper place to get at it with the case on. The opening around the plug may also need adjusting, but it should work with many Micro-USB cables if that is what you decide to use.

Sensor Voltage

If you are using a pro-micro or compatible, it's probably running at 5v. By default, the sensor unit is setup to run at 3.3v. Here is an image, and the description from the vendors website:

Voltage Selection

If you are using Arduino or another similar microcontroller that has a native 5V core voltage, you'll need to activate 5V mode by cutting the tiny traces between the three sets of exposed pads on the 3.3V side of the board and adding three solder bridges to the exposed pads on the 5V side of the board. I recommend an exacto knife. Please be careful not to cut any other nearby traces. Both sets of pads can be found on the backside of the circuit board. This is the most common issue that causes non-communication.

Wiring

Wiring

The diagram above shows the correct connections to make and the suggested pins to use.

  • White: VCC +5v
  • Grey: Ground. Note that this is bridged between the analog and digital ground on the sensor
  • Red, Orange, Yellow: SPI Bus connections, these can't be relocated
  • Green: Select line... any digital pin will do but this is the most convineint location.

You can see the routing of the wires in the image at the top of this page. I suggest stripping both ends of the wires before starting to solder them. You have some room to work, but keeping the wires short-ish is helpful. You'll have to solder these wires from the top side sticking out the back of the MCU.

Soldering

Here is a photo after all the wires attached to the MCU, with a ruler to show how long I made them.

Wire Length

Make sure you have the sensor oriented correctly, and follow the wiring diagram to connect the wires to the MCU and finish this step up.

Testing

This is a great time to plug the MCU back into your computer. You can place the lens on top of the sensor unit and just run your finger over the sensor. You should see the cursor on screen move. If so, you are all set to go with the mechanical assembly!