Merge remote-tracking branch 'upstream/master'

* upstream/master: (1239 commits)
  Update ez.c
  removes planck/rev3 temporarily
  Move hand_swap_config to ez.c, removes error for infinity
  Update Makefile
  ergodox: Update algernon's keymap to v1.9
  Added VS Code dir to .gitignore
  Support the Pegasus Hoof controller.
  [Jack & Erez] Simplifies and documents TO
  add readme
  use wait_ms instead of _delay_ms
  add messenger
  init keymap
  Add example keymap
  Adding whiskey_tango_foxtrot_capslock ergodox keymap
  Unicode map framework. Allow unicode up to 0xFFFFF using separate mapping table
  CIE 1931 dim curve
  Apply the dim curve to the RGB output
  Update the Cluecard readme files
  Tune snake and knight intervals for Cluecard
  Tunable RGB light intervals
  ...

1 files changed, 102 insertions, 0 deletions

diff --git a/keyboards/lets_split/readme.md b/keyboards/lets_split/readme.md
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+Let's Split
+======
+
+This readme and most of the code are from https://github.com/ahtn/tmk_keyboard/
+
+Split keyboard firmware for Arduino Pro Micro or other ATmega32u4
+based boards.
+
+Features
+--------
+
+Some features supported by the firmware:
+
+* Either half can connect to the computer via USB, or both halves can be used
+  independently.
+* You only need 3 wires to connect the two halves. Two for VCC and GND and one
+  for serial communication.
+* Optional support for I2C connection between the two halves if for some
+  reason you require a faster connection between the two halves. Note this
+  requires an extra wire between halves and pull-up resistors on the data lines.
+
+Required Hardware
+-----------------
+
+Apart from diodes and key switches for the keyboard matrix in each half, you
+will need:
+
+* 2 Arduino Pro Micro's. You can find theses on aliexpress for ≈3.50USD each.
+* 2 TRS sockets
+* 1 TRS cable.
+
+Alternatively, you can use any sort of cable and socket that has at least 3
+wires. If you want to use I2C to communicate between halves, you will need a
+cable with at least 4 wires and 2x 4.7kΩ pull-up resistors
+
+Optional Hardware
+-----------------
+
+A speaker can be hooked-up to either side to the `5` (`C6`) pin and `GND`, and turned on via `AUDIO_ENABLE`.
+
+Wiring
+------
+
+The 3 wires of the TRS cable need to connect GND, VCC, and digital pin 3 (i.e.
+PD0 on the ATmega32u4) between the two Pro Micros.
+
+Then wire your key matrix to any of the remaining 17 IO pins of the pro micro
+and modify the `matrix.c` accordingly.
+
+The wiring for serial:
+
+![serial wiring](imgs/split-keyboard-serial-schematic.png)
+
+The wiring for i2c:
+
+![i2c wiring](imgs/split-keyboard-i2c-schematic.png)
+
+The pull-up resistors may be placed on either half. It is also possible
+to use 4 resistors and have the pull-ups in both halves, but this is
+unnecessary in simple use cases.
+
+Notes on Software Configuration
+-------------------------------
+
+Configuring the firmware is similar to any other TMK project. One thing
+to note is that `MATIX_ROWS` in `config.h` is the total number of rows between
+the two halves, i.e. if your split keyboard has 4 rows in each half, then
+`MATRIX_ROWS=8`.
+
+Also the current implementation assumes a maximum of 8 columns, but it would
+not be very difficult to adapt it to support more if required.
+
+
+Flashing
+--------
+
+If you define `EE_HANDS` in your `config.h`, you will need to set the
+EEPROM for the left and right halves. The EEPROM is used to store whether the
+half is left handed or right handed. This makes it so that the same firmware
+file will run on both hands instead of having to flash left and right handed
+versions of the firmware to each half. To flash the EEPROM file for the left
+half run:
+```
+make eeprom-left
+```
+and similarly for right half
+```
+make eeprom-right
+```
+
+After you have flashed the EEPROM for the first time, you then need to program
+the flash memory:
+```
+make program
+```
+Note that you need to program both halves, but you have the option of using
+different keymaps for each half. You could program the left half with a QWERTY
+layout and the right half with a Colemak layout. Then if you connect the left
+half to a computer by USB the keyboard will use QWERTY and Colemak when the
+right half is connected.
+
+