Pimoroni Trackball Integration

Adding the Pimoroni trackball to QMK-compatible keyboards

09-29-21

Table of Contents

• Pro Micro
• Trackball
• Firmware
• config.h
• rules.mk
• keymap.c
• Flashing
• Resources

Pro Micro

Two SparkFun Qwiic Pro Micro C will be used.

The trackball will connect to the master half of the board. The 5V and VCC pads must be bridged.

The slave half must have the 5V pad broken which can be carefully cut with an Xacto knife or similar.

In order to flash the left half, the RAW and 5V pins must be bridged. A trace wire can be soldered to the RAW pin (pictured above) to conveniently hold against the 5V pin when flashing. Ensure the wire does not make any connections when powered on and in use.

Trackball

One Pimoroni Trackball Breakout will be used. It will connect to the Pro Micro C via the Qwiic Cable Kit. All that is necessary is one Quiic connection cable, not the entire kit, but it’s nice to have extra. The trackball rests in place of the OLED display via a 3D-printed cover.

The Quiic cable is soldered to the bottom of the Pimoroni.

GND	INT	SCL	SDA	3-5V
BLACK	(NONE)	YELLOW	BLUE	RED

Cut the wires short enough to prevent them from bunching up under the cover.

Place a layer of electrical tape between the microcontroller and the trackball unit to prevent the screws and nuts from contacting the pins.

Presto!

Firmware

config.h

#define EE_HANDS
#define PIMORONI_TRACKBALL_ROTATE
#define PIMORONI_TRACKBALL_INVERT_X

rules.mk

PIMORONI_TRACKBALL_ENABLE = yes

ifeq ($(strip $(PIMORONI_TRACKBALL_ENABLE)), yes)
 POINTING_DEVICE_ENABLE = yes
 SRC += drivers/sensors/pimoroni_trackball.c
 QUANTUM_LIB_SRC += i2c_master.c
endif

keymap.c

#ifdef PIMORONI_TRACKBALL_ENABLE
#include "drivers/sensors/pimoroni_trackball.h"
#endif

enum trackball_keycodes {
 BALL_SCR
};

uint8_t MOUSE_BUTTONS;

#ifdef PIMORONI_TRACKBALL_ENABLE

void pointing_device_task() {
    report_mouse_t mouse_report = pointing_device_get_report();
    mouse_report.buttons = MOUSE_BUTTONS;

    if (is_keyboard_master()) {
        process_mouse(&mouse_report);
    }
    case BALL_SCR:
     if(record->event.pressed){
    trackball_set_scrolling(true);
     } else{
    trackball_set_scrolling(false);
    }

    pointing_device_set_report(mouse_report);
    pointing_device_send();
}

#endif

BALL_SCR (scrolling in general) is not working for me.

Map KC_BTN(1-5) for mouse buttons.

Flashing

Each hand will be flashed with an indivdual EEPROM. The Pro Micro C uses the Caterina bootloader and will be can be flashed using avrdude.

In the qmk_firmware directory:

make crkbd:<keymap>:avrdude-split-<hand>

where <keymap> is the name of the keymap and <hand> is the hand being flashed (left, right).

To put the Pro Micro C into a writeable state, the reset button must be pushed quickly twice, not once.

Before flashing the left hand, bridge the RAW and 5V pins (see above).

Resources

Below are the guides I referenced and servers I asked in to get my trackball working.

foureight84 - sofle-keyboard-pimoroni

greyhatmiddleman - crkbd-pimoroni-trackball

QMK Discord - #help-firmare, #help-hardware

Boardsource Discord - #firmware

~~~

-medwa

Tagged: keyboards