100 lines
3.2 KiB
Markdown
100 lines
3.2 KiB
Markdown
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This is a modification of the TMK firmware by ahtn found here https://github.com/ahtn/tmk_keyboard/tree/master/keyboard/split_keyboard
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Custom split keyboard firmware
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======
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Split keyboard firmware for Arduino Pro Micro or other ATmega32u4
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based boards.
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Features
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--------
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Some features supported by the firmware:
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* Either half can connect to the computer via USB, or both halves can be used
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independently.
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* You only need 3 wires to connect the two halves. Two for VCC and GND and one
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for serial communication.
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* Optional support for I2C connection between the two halves if for some
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reason you require a faster connection between the two halves. Note this
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requires an extra wire between halves and pull-up resistors on the data lines.
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Required Hardware
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-----------------
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Apart from diodes and key switches for the keyboard matrix in each half, you
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will need:
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* 2 Arduino Pro Micro's. You can find theses on aliexpress for ≈3.50USD each.
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* 2 TRS sockets
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* 1 TRS cable.
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Alternatively, you can use any sort of cable and socket that has at least 3
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wires. If you want to use I2C to communicate between halves, you will need a
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cable with at least 4 wires and 2x 4.7kΩ pull-up resistors
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Wiring
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------
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The 3 wires of the TRS cable need to connect GND, VCC, and digital pin 3 (i.e.
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`PD0` on the ATmega32u4) between the two Pro Micros.
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Then wire your key matrix to any of the remaining 17 IO pins of the pro micro
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and modify the `MATRIX_COL_PINS` and `MATRIX_ROW_PINS` in `config.h` accordingly.
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The wiring for serial:
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The wiring for i2c:
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The pull-up resistors may be placed on either half. It is also possible
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to use 4 resistors and have the pull-ups in both halves, but this is
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unnecessary in simple use cases.
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Notes on Software Configuration
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-------------------------------
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Configuring the firmware is similar to any other TMK project. One thing
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to note is that `MATIX_ROWS` in `config.h` is the total number of rows between
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the two halves, i.e. if your split keyboard has 4 rows in each half, then
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`MATRIX_ROWS=8`.
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Also the current implementation assumes a maximum of 8 columns, but it would
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not be very difficult to adapt it to support more if required.
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Flashing
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--------
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Before you go to flash the program memory for the first time, you will need to
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EEPROM for the left and right halves. The EEPROM is used to store whether the
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half is left handed or right handed. This makes it so that the same firmware
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file will run on both hands instead of having to flash left and right handed
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versions of the firmware to each half. To flash the EEPROM file for the left
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half run:
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```
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make eeprom-left
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```
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and similarly for right half
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```
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make eeprom-right
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```
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After you have flashed the EEPROM for the first time, you then need to program
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the flash memory:
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```
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make program
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```
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Note that you need to program both halves, but you have the option of using
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different keymaps for each half. You could program the left half with a QWERTY
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layout and the right half with a Colemak layout. Then if you connect the left
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half to a computer by USB the keyboard will use QWERTY and Colemak when the
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right half is connected.
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