4 This readme and most of the code are from https://github.com/ahtn/tmk_keyboard/
6 Split keyboard firmware for Arduino Pro Micro or other ATmega32u4
12 Some features supported by the firmware:
14 * Either half can connect to the computer via USB, or both halves can be used
16 * You only need 3 wires to connect the two halves. Two for VCC and GND and one
17 for serial communication.
18 * Optional support for I2C connection between the two halves if for some
19 reason you require a faster connection between the two halves. Note this
20 requires an extra wire between halves and pull-up resistors on the data lines.
25 Apart from diodes and key switches for the keyboard matrix in each half, you
28 * 2 Arduino Pro Micro's. You can find theses on aliexpress for ≈3.50USD each.
32 Alternatively, you can use any sort of cable and socket that has at least 3
33 wires. If you want to use I2C to communicate between halves, you will need a
34 cable with at least 4 wires and 2x 4.7kΩ pull-up resistors
39 A speaker can be hooked-up to either side to the `5` (`C6`) pin and `GND`, and turned on via `AUDIO_ENABLE`.
44 The 3 wires of the TRS cable need to connect GND, VCC, and digital pin 3 (i.e.
45 PD0 on the ATmega32u4) between the two Pro Micros.
47 Then wire your key matrix to any of the remaining 17 IO pins of the pro micro
48 and modify the `matrix.c` accordingly.
50 The wiring for serial:
52 ![serial wiring](imgs/split-keyboard-serial-schematic.png)
56 ![i2c wiring](imgs/split-keyboard-i2c-schematic.png)
58 The pull-up resistors may be placed on either half. It is also possible
59 to use 4 resistors and have the pull-ups in both halves, but this is
60 unnecessary in simple use cases.
62 Notes on Software Configuration
63 -------------------------------
65 Configuring the firmware is similar to any other TMK project. One thing
66 to note is that `MATIX_ROWS` in `config.h` is the total number of rows between
67 the two halves, i.e. if your split keyboard has 4 rows in each half, then
70 Also the current implementation assumes a maximum of 8 columns, but it would
71 not be very difficult to adapt it to support more if required.
77 If you define `EE_HANDS` in your `config.h`, you will need to set the
78 EEPROM for the left and right halves. The EEPROM is used to store whether the
79 half is left handed or right handed. This makes it so that the same firmware
80 file will run on both hands instead of having to flash left and right handed
81 versions of the firmware to each half. To flash the EEPROM file for the left
86 and similarly for right half
91 After you have flashed the EEPROM for the first time, you then need to program
96 Note that you need to program both halves, but you have the option of using
97 different keymaps for each half. You could program the left half with a QWERTY
98 layout and the right half with a Colemak layout. Then if you connect the left
99 half to a computer by USB the keyboard will use QWERTY and Colemak when the
100 right half is connected.
103 Notes on Using Pro Micro 3.3V
104 -----------------------------
106 Do update the `F_CPU` parameter in `rules.mk` to `8000000` which reflects
107 the frequency on the 3.3V board.
109 Also, if the slave board is producing weird characters in certain columns,
110 update the following line in `matrix.c` to the following:
113 // _delay_us(30); // without this wait read unstable value.
114 _delay_us(300); // without this wait read unstable value.