scroll-ring-trackball's Introduction

DIY trackball with scroll ring

This repository contains design files and code that can be used to make a fully programmable four-button USB trackball with a scroll ring.

It uses the following components:

57.2mm billiard ball
PMW3360 optical sensor
RP2040+PMW3360 PCB
button switch mount PCBs
3D printed case
Omron D2FC switches (or similar)
2x SS49E Hall effect sensors (TO-92 package)
72x 2x2mm neodymium cylinder magnets (axially magnetized)
60x78x10mm bearing (6812 ZZ)
2.5mm zirconium oxide (or silicon nitride) bearing balls
M3x4 screws for mounting the main PCB and assembling the case
M2x4 screws for mounting the buttons and the secondary PCBs
USB cable (cut off the device end and solder the wires directly to the PCB)
some hookup wire

The main PCB uses the RP2040 chip from Raspberry Pi. The firmware supports remapping of ball, button and ring functions using a configuration tool without the need to recompile the source code. All the configuration is stored on device, so the configuration tool is only needed to change the settings, not during normal use.

So far I only tested the configuration tool on Linux, but it should in theory run on Windows and Mac as well. I will try to provide ready-to-use packages in the future.

The provided UF2 file can be used to flash the firmware onto the device. When first connected, a "RPI-RP2" drive will show up and you flash the chip by copying the UF2 file to that drive. If you want to flash it again, hold the BOOT button and press the RESET button on the board.

I printed the case parts with 0.2mm layer height. They don't need supports.

The bearing and the magnets are press-fit into the case, but depending on your particular printer you might want to use glue. The Hall effect sensors should be oriented "face-up" and will definitely need some glue to stay in place.

The magnets should be installed with alternating polarity (the outside-facing pole should be N-S-N-S... etc.).

The Hall sensors' + leads are connected to 3.3V. The rest of the pin numbers are defined at the top of trackball.cc.

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scroll-ring-trackball's Issues

need a breakout pcb for the scroll ring encoders.

there should be kicad files for a simple pcb that carries the vcc and gnd between both hall effect sensors, the pcb would have a hole to screw it to the top stl. the pcb would prevent the legs of the hall effect sensors from shorting together. the pcb would have headers for the 4 wires, 3.3v, gnd, and the two sensor pins.

also the button switch pcb should have a location for a through hole pullup resistor (to avoid smt assembly cost), and an extra header for 3.3v. It would be better if each button switch pcb had two headers for gnd and two for 3.3v. that is so that you can daisy chain a wire from one switch to the next, rather than having a large bundle of grounds tied together that could short something out if moved.

suggested modifications to the 3d print

I've built this and you've seen the image i linked on twitter. however there's a few issues,

one is that there's no way to move the trackball without clicking the buttons. this could be remedied by raising the outer wall to 1 1/2 times the existing height on the bottom stl. this requires the buttons acute edge to be truncated so that they do not hit the wall. i have filed down the buttons on my build so that i can lift it and it works.

another idea is to allow the use of the internals from the two ball trackball. this would allow high definition scrolling. this can be accomplished by rotating each of the 4 base standoffs 45 degrees, along with the matching holes in the ring stl. the room this makes would allow the second pmw3360 sensor to be placed between the screw holes of either button closest to the usb cable entry point. there would need to be a hole made in the ring stl to accept the lens.

These modifications will work fine with the existing hall sensor, as well as the two ball pcbs, leaving the assembly up to the user.

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scroll-ring-trackball's Introduction

DIY trackball with scroll ring

scroll-ring-trackball's People

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scroll-ring-trackball's Issues

need a breakout pcb for the scroll ring encoders.

suggested modifications to the 3d print

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