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 A build guide for putting together the Let's Split v2 can be found here: [An Overly Verbose Guide to Building a Let's Split Keyboard](https://github.com/nicinabox/lets-split-guide)
14 There is additional information there about flashing and adding RGB underglow.
18 Download or clone the whole firmware and navigate to the keyboards/lets_split directory. Once your dev env is setup, you'll be able to generate the default .hex using:
24 You will see a lot of output and if everything worked correctly you will see the built hex files:
27 lets_split_rev2_serial.hex
28 lets_split_rev2_i2c.hex
31 If you would like to use one of the alternative keymaps, or create your own, copy one of the existing [keymaps](keymaps/) and run make like so:
35 $ make rev2-YOUR_KEYMAP_NAME
38 If everything worked correctly you will see a file:
41 lets_split_rev2_YOUR_KEYMAP_NAME.hex
44 For more information on customizing keymaps, take a look at the primary documentation for [Customizing Your Keymap](/readme.md##customizing-your-keymap) in the main readme.md.
47 If you have a first generation Let's Split you will need to use the revision 1 code. To do so, use `rev1` in all your commands instead.
52 For the full Quantum Mechanical Keyboard feature list, see [the parent readme.md](/readme.md).
54 Some features supported by the firmware:
56 * Either half can connect to the computer via USB, or both halves can be used
58 * You only need 3 wires to connect the two halves. Two for VCC and GND and one
59 for serial communication.
60 * Optional support for I2C connection between the two halves if for some
61 reason you require a faster connection between the two halves. Note this
62 requires an extra wire between halves and pull-up resistors on the data lines.
67 Apart from diodes and key switches for the keyboard matrix in each half, you
70 * 2 Arduino Pro Micro's. You can find theses on aliexpress for ≈3.50USD each.
71 * 2 TRRS sockets and 1 TRRS cable, or 2 TRS sockets and 1 TRS cable
73 Alternatively, you can use any sort of cable and socket that has at least 3
74 wires. If you want to use I2C to communicate between halves, you will need a
75 cable with at least 4 wires and 2x 4.7kΩ pull-up resistors
80 A speaker can be hooked-up to either side to the `5` (`C6`) pin and `GND`, and turned on via `AUDIO_ENABLE`.
85 The 3 wires of the TRS/TRRS cable need to connect GND, VCC, and digital pin 3 (i.e.
86 PD0 on the ATmega32u4) between the two Pro Micros.
88 Then wire your key matrix to any of the remaining 17 IO pins of the pro micro
89 and modify the `matrix.c` accordingly.
91 The wiring for serial:
93 ![serial wiring](imgs/split-keyboard-serial-schematic.png)
97 ![i2c wiring](imgs/split-keyboard-i2c-schematic.png)
99 The pull-up resistors may be placed on either half. It is also possible
100 to use 4 resistors and have the pull-ups in both halves, but this is
101 unnecessary in simple use cases.
103 Notes on Software Configuration
104 -------------------------------
106 Configuring the firmware is similar to any other QMK project. One thing
107 to note is that `MATIX_ROWS` in `config.h` is the total number of rows between
108 the two halves, i.e. if your split keyboard has 4 rows in each half, then
111 Also the current implementation assumes a maximum of 8 columns, but it would
112 not be very difficult to adapt it to support more if required.
116 From the keymap directory run `make SUBPROJECT-KEYMAP-avrdude` for automatic serial port resolution and flashing.
117 Example: `make rev2-serial-avrdude`
120 Choosing which board to plug the USB cable into (choosing Master)
122 Because the two boards are identical, the firmware has logic to differentiate the left and right board.
124 It uses two strategies to figure things out: look at the EEPROM (memory on the chip) or looks if the current board has the usb cable.
126 The EEPROM approach requires additional setup (flashing the eeeprom) but allows you to swap the usb cable to either side.
128 The USB cable approach is easier to setup and if you just want the usb cable on the left board, you do not need to do anything extra.
130 ### Setting the left hand as master
131 If you always plug the usb cable into the left board, nothing extra is needed as this is the default. Comment out `EE_HANDS` and comment out `I2C_MASTER_RIGHT` or `MASTER_RIGHT` if for some reason it was set.
133 ### Setting the right hand as master
134 If you always plug the usb cable into the right board, add an extra flag to your `config.h`
139 ### Setting EE_hands to use either hands as master
140 If you define `EE_HANDS` in your `config.h`, you will need to set the
141 EEPROM for the left and right halves.
143 The EEPROM is used to store whether the
144 half is left handed or right handed. This makes it so that the same firmware
145 file will run on both hands instead of having to flash left and right handed
146 versions of the firmware to each half. To flash the EEPROM file for the left
149 avrdude -p atmega32u4 -P $(COM_PORT) -c avr109 -U eeprom:w:eeprom-lefthand.eep
150 // or the equivalent in dfu-programmer
153 and similarly for right half
155 avrdude -p atmega32u4 -P $(COM_PORT) -c avr109 -U eeprom:w:eeprom-righhand.eep
156 // or the equivalent in dfu-programmer
159 NOTE: replace `$(COM_PORT)` with the port of your device (e.g. `/dev/ttyACM0`)
161 After you have flashed the EEPROM, you then need to set `EE_HANDS` in your config.h, rebuild the hex files and reflash.
163 Note that you need to program both halves, but you have the option of using
164 different keymaps for each half. You could program the left half with a QWERTY
165 layout and the right half with a Colemak layout using bootmagic's default layout option.
166 Then if you connect the left half to a computer by USB the keyboard will use QWERTY and Colemak when the
167 right half is connected.
170 Notes on Using Pro Micro 3.3V
171 -----------------------------
173 Do update the `F_CPU` parameter in `rules.mk` to `8000000` which reflects
174 the frequency on the 3.3V board.
176 Also, if the slave board is producing weird characters in certain columns,
177 update the following line in `matrix.c` to the following:
180 // _delay_us(30); // without this wait read unstable value.
181 _delay_us(300); // without this wait read unstable value.