Keyboard firmwares for Atmel AVR and Cortex-M
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  1. This is a modification of the TMK firmware by ahtn found here
  2. Custom split keyboard firmware
  3. ======
  4. Split keyboard firmware for Arduino Pro Micro or other ATmega32u4
  5. based boards.
  6. Features
  7. --------
  8. Some features supported by the firmware:
  9. * Either half can connect to the computer via USB, or both halves can be used
  10. independently.
  11. * You only need 3 wires to connect the two halves. Two for VCC and GND and one
  12. for serial communication.
  13. * Optional support for I2C connection between the two halves if for some
  14. reason you require a faster connection between the two halves. Note this
  15. requires an extra wire between halves and pull-up resistors on the data lines.
  16. Required Hardware
  17. -----------------
  18. Apart from diodes and key switches for the keyboard matrix in each half, you
  19. will need:
  20. * 2 Arduino Pro Micro's. You can find theses on aliexpress for ≈3.50USD each.
  21. * 2 TRS sockets
  22. * 1 TRS cable.
  23. Alternatively, you can use any sort of cable and socket that has at least 3
  24. wires. If you want to use I2C to communicate between halves, you will need a
  25. cable with at least 4 wires and 2x 4.7kΩ pull-up resistors
  26. Wiring
  27. ------
  28. The 3 wires of the TRS cable need to connect GND, VCC, and digital pin 3 (i.e.
  29. `PD0` on the ATmega32u4) between the two Pro Micros.
  30. Then wire your key matrix to any of the remaining 17 IO pins of the pro micro
  31. and modify the `MATRIX_COL_PINS` and `MATRIX_ROW_PINS` in `config.h` accordingly.
  32. The wiring for serial:
  33. ![serial wiring](imgs/split-keyboard-serial-schematic.png)
  34. The wiring for i2c:
  35. ![i2c wiring](imgs/split-keyboard-i2c-schematic.png)
  36. The pull-up resistors may be placed on either half. It is also possible
  37. to use 4 resistors and have the pull-ups in both halves, but this is
  38. unnecessary in simple use cases.
  39. Notes on Software Configuration
  40. -------------------------------
  41. Configuring the firmware is similar to any other TMK project. One thing
  42. to note is that `MATIX_ROWS` in `config.h` is the total number of rows between
  43. the two halves, i.e. if your split keyboard has 4 rows in each half, then
  44. `MATRIX_ROWS=8`.
  45. Also the current implementation assumes a maximum of 8 columns, but it would
  46. not be very difficult to adapt it to support more if required.
  47. Flashing
  48. --------
  49. Before you go to flash the program memory for the first time, you will need to
  50. EEPROM for the left and right halves. The EEPROM is used to store whether the
  51. half is left handed or right handed. This makes it so that the same firmware
  52. file will run on both hands instead of having to flash left and right handed
  53. versions of the firmware to each half. To flash the EEPROM file for the left
  54. half run:
  55. ```
  56. make eeprom-left
  57. ```
  58. and similarly for right half
  59. ```
  60. make eeprom-right
  61. ```
  62. After you have flashed the EEPROM for the first time, you then need to program
  63. the flash memory:
  64. ```
  65. make program
  66. ```
  67. Note that you need to program both halves, but you have the option of using
  68. different keymaps for each half. You could program the left half with a QWERTY
  69. layout and the right half with a Colemak layout. Then if you connect the left
  70. half to a computer by USB the keyboard will use QWERTY and Colemak when the
  71. right half is connected.