diff --git a/keyboards/lets_split/imgs/split-keyboard-i2c-schematic.png b/keyboards/lets_split/imgs/split-keyboard-i2c-schematic.png
new file mode 100644
index 00000000..88829471
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diff --git a/keyboards/lets_split/imgs/split-keyboard-serial-schematic.png b/keyboards/lets_split/imgs/split-keyboard-serial-schematic.png
new file mode 100644
index 00000000..7621d38e
Binary files /dev/null and b/keyboards/lets_split/imgs/split-keyboard-serial-schematic.png differ
diff --git a/keyboards/lets_split/matrix.c b/keyboards/lets_split/matrix.c
index 16c2ba0b..1d768c59 100644
--- a/keyboards/lets_split/matrix.c
+++ b/keyboards/lets_split/matrix.c
@@ -29,6 +29,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #include "util.h"
 #include "matrix.h"
 #include "i2c.h"
+#include "serial.h"
 #include "split_util.h"
 #include "pro_micro.h"
 #include "config.h"
diff --git a/keyboards/lets_split/readme.md b/keyboards/lets_split/readme.md
index e69de29b..73fdb0f7 100644
--- a/keyboards/lets_split/readme.md
+++ b/keyboards/lets_split/readme.md
@@ -0,0 +1,102 @@
+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.
+
+
diff --git a/keyboards/lets_split/serial.c b/keyboards/lets_split/serial.c
new file mode 100644
index 00000000..f439c2f2
--- /dev/null
+++ b/keyboards/lets_split/serial.c
@@ -0,0 +1,225 @@
+/*
+ * WARNING: be careful changing this code, it is very timing dependent
+ */
+
+#ifndef F_CPU
+#define F_CPU 16000000
+#endif
+
+#include <avr/io.h>
+#include <avr/interrupt.h>
+#include <util/delay.h>
+#include <stdbool.h>
+
+#include "serial.h"
+
+// Serial pulse period in microseconds. Its probably a bad idea to lower this
+// value.
+#define SERIAL_DELAY 24
+
+uint8_t volatile serial_slave_buffer[SERIAL_SLAVE_BUFFER_LENGTH] = {0};
+uint8_t volatile serial_master_buffer[SERIAL_MASTER_BUFFER_LENGTH] = {0};
+
+#define SLAVE_DATA_CORRUPT (1<<0)
+volatile uint8_t status = 0;
+
+inline static
+void serial_delay(void) {
+  _delay_us(SERIAL_DELAY);
+}
+
+inline static
+void serial_output(void) {
+  SERIAL_PIN_DDR |= SERIAL_PIN_MASK;
+}
+
+// make the serial pin an input with pull-up resistor
+inline static
+void serial_input(void) {
+  SERIAL_PIN_DDR  &= ~SERIAL_PIN_MASK;
+  SERIAL_PIN_PORT |= SERIAL_PIN_MASK;
+}
+
+inline static
+uint8_t serial_read_pin(void) {
+  return !!(SERIAL_PIN_INPUT & SERIAL_PIN_MASK);
+}
+
+inline static
+void serial_low(void) {
+  SERIAL_PIN_PORT &= ~SERIAL_PIN_MASK;
+}
+
+inline static
+void serial_high(void) {
+  SERIAL_PIN_PORT |= SERIAL_PIN_MASK;
+}
+
+void serial_master_init(void) {
+  serial_output();
+  serial_high();
+}
+
+void serial_slave_init(void) {
+  serial_input();
+
+  // Enable INT0
+  EIMSK |= _BV(INT0);
+  // Trigger on falling edge of INT0
+  EICRA &= ~(_BV(ISC00) | _BV(ISC01));
+}
+
+// Used by the master to synchronize timing with the slave.
+static
+void sync_recv(void) {
+  serial_input();
+  // This shouldn't hang if the slave disconnects because the
+  // serial line will float to high if the slave does disconnect.
+  while (!serial_read_pin());
+  serial_delay();
+}
+
+// Used by the slave to send a synchronization signal to the master.
+static
+void sync_send(void) {
+  serial_output();
+
+  serial_low();
+  serial_delay();
+
+  serial_high();
+}
+
+// Reads a byte from the serial line
+static
+uint8_t serial_read_byte(void) {
+  uint8_t byte = 0;
+  serial_input();
+  for ( uint8_t i = 0; i < 8; ++i) {
+    byte = (byte << 1) | serial_read_pin();
+    serial_delay();
+    _delay_us(1);
+  }
+
+  return byte;
+}
+
+// Sends a byte with MSB ordering
+static
+void serial_write_byte(uint8_t data) {
+  uint8_t b = 8;
+  serial_output();
+  while( b-- ) {
+    if(data & (1 << b)) {
+      serial_high();
+    } else {
+      serial_low();
+    }
+    serial_delay();
+  }
+}
+
+// interrupt handle to be used by the slave device
+ISR(SERIAL_PIN_INTERRUPT) {
+  sync_send();
+
+  uint8_t checksum = 0;
+  for (int i = 0; i < SERIAL_SLAVE_BUFFER_LENGTH; ++i) {
+    serial_write_byte(serial_slave_buffer[i]);
+    sync_send();
+    checksum += serial_slave_buffer[i];
+  }
+  serial_write_byte(checksum);
+  sync_send();
+
+  // wait for the sync to finish sending
+  serial_delay();
+
+  // read the middle of pulses
+  _delay_us(SERIAL_DELAY/2);
+
+  uint8_t checksum_computed = 0;
+  for (int i = 0; i < SERIAL_MASTER_BUFFER_LENGTH; ++i) {
+    serial_master_buffer[i] = serial_read_byte();
+    sync_send();
+    checksum_computed += serial_master_buffer[i];
+  }
+  uint8_t checksum_received = serial_read_byte();
+  sync_send();
+
+  serial_input(); // end transaction
+
+  if ( checksum_computed != checksum_received ) {
+    status |= SLAVE_DATA_CORRUPT;
+  } else {
+    status &= ~SLAVE_DATA_CORRUPT;
+  }
+}
+
+inline
+bool serial_slave_DATA_CORRUPT(void) {
+  return status & SLAVE_DATA_CORRUPT;
+}
+
+// Copies the serial_slave_buffer to the master and sends the
+// serial_master_buffer to the slave.
+//
+// Returns:
+// 0 => no error
+// 1 => slave did not respond
+int serial_update_buffers(void) {
+  // this code is very time dependent, so we need to disable interrupts
+  cli();
+
+  // signal to the slave that we want to start a transaction
+  serial_output();
+  serial_low();
+  _delay_us(1);
+
+  // wait for the slaves response
+  serial_input();
+  serial_high();
+  _delay_us(SERIAL_DELAY);
+
+  // check if the slave is present
+  if (serial_read_pin()) {
+    // slave failed to pull the line low, assume not present
+    sei();
+    return 1;
+  }
+
+  // if the slave is present syncronize with it
+  sync_recv();
+
+  uint8_t checksum_computed = 0;
+  // receive data from the slave
+  for (int i = 0; i < SERIAL_SLAVE_BUFFER_LENGTH; ++i) {
+    serial_slave_buffer[i] = serial_read_byte();
+    sync_recv();
+    checksum_computed += serial_slave_buffer[i];
+  }
+  uint8_t checksum_received = serial_read_byte();
+  sync_recv();
+
+  if (checksum_computed != checksum_received) {
+    sei();
+    return 1;
+  }
+
+  uint8_t checksum = 0;
+  // send data to the slave
+  for (int i = 0; i < SERIAL_MASTER_BUFFER_LENGTH; ++i) {
+    serial_write_byte(serial_master_buffer[i]);
+    sync_recv();
+    checksum += serial_master_buffer[i];
+  }
+  serial_write_byte(checksum);
+  sync_recv();
+
+  // always, release the line when not in use
+  serial_output();
+  serial_high();
+
+  sei();
+  return 0;
+}
diff --git a/keyboards/lets_split/serial.h b/keyboards/lets_split/serial.h
new file mode 100644
index 00000000..15fe4db7
--- /dev/null
+++ b/keyboards/lets_split/serial.h
@@ -0,0 +1,26 @@
+#ifndef MY_SERIAL_H
+#define MY_SERIAL_H
+
+#include "config.h"
+#include <stdbool.h>
+
+/* TODO:  some defines for interrupt setup */
+#define SERIAL_PIN_DDR DDRD
+#define SERIAL_PIN_PORT PORTD
+#define SERIAL_PIN_INPUT PIND
+#define SERIAL_PIN_MASK _BV(PD0)
+#define SERIAL_PIN_INTERRUPT INT0_vect
+
+#define SERIAL_SLAVE_BUFFER_LENGTH MATRIX_ROWS/2
+#define SERIAL_MASTER_BUFFER_LENGTH 1
+
+// Buffers for master - slave communication
+extern volatile uint8_t serial_slave_buffer[SERIAL_SLAVE_BUFFER_LENGTH];
+extern volatile uint8_t serial_master_buffer[SERIAL_MASTER_BUFFER_LENGTH];
+
+void serial_master_init(void);
+void serial_slave_init(void);
+int serial_update_buffers(void);
+bool serial_slave_data_corrupt(void);
+
+#endif
diff --git a/keyboards/lets_split/split_util.c b/keyboards/lets_split/split_util.c
index c394596e..65003a71 100644
--- a/keyboards/lets_split/split_util.c
+++ b/keyboards/lets_split/split_util.c
@@ -7,13 +7,22 @@
 #include "split_util.h"
 #include "matrix.h"
 #include "i2c.h"
+#include "serial.h"
 #include "keyboard.h"
 #include "config.h"
 
 volatile bool isLeftHand = true;
 
 static void setup_handedness(void) {
+  #ifdef EE_HANDS
     isLeftHand = eeprom_read_byte(EECONFIG_HANDEDNESS);
+  #else
+    #ifdef I2C_MASTER_RIGHT
+      isLeftHand = !has_usb();
+    #else
+      isLeftHand = has_usb();
+    #endif
+  #endif
 }
 
 static void keyboard_master_setup(void) {
diff --git a/keyboards/lets_split/split_util.h b/keyboards/lets_split/split_util.h
index cf6890d3..6b896679 100644
--- a/keyboards/lets_split/split_util.h
+++ b/keyboards/lets_split/split_util.h
@@ -3,8 +3,10 @@
 
 #include <stdbool.h>
 
-#define EECONFIG_BOOTMAGIC_END      (uint8_t *)10
-#define EECONFIG_HANDEDNESS         EECONFIG_BOOTMAGIC_END
+#ifdef EE_HANDS
+	#define EECONFIG_BOOTMAGIC_END      (uint8_t *)10
+	#define EECONFIG_HANDEDNESS         EECONFIG_BOOTMAGIC_END
+#endif
 
 #define SLAVE_I2C_ADDRESS           0x32
 
diff --git a/keyboards/lets_split/uno-slave/Makefile b/keyboards/lets_split/uno_slave/Makefile
similarity index 100%
rename from keyboards/lets_split/uno-slave/Makefile
rename to keyboards/lets_split/uno_slave/Makefile
diff --git a/keyboards/lets_split/uno-slave/keyboard-i2c-slave.c b/keyboards/lets_split/uno_slave/keyboard-i2c-slave.c
similarity index 100%
rename from keyboards/lets_split/uno-slave/keyboard-i2c-slave.c
rename to keyboards/lets_split/uno_slave/keyboard-i2c-slave.c
diff --git a/keyboards/lets_split/uno-slave/readme.md b/keyboards/lets_split/uno_slave/readme.md
similarity index 100%
rename from keyboards/lets_split/uno-slave/readme.md
rename to keyboards/lets_split/uno_slave/readme.md
diff --git a/keyboards/lets_split/uno-slave/uno-matrix.c b/keyboards/lets_split/uno_slave/uno-matrix.c
similarity index 100%
rename from keyboards/lets_split/uno-slave/uno-matrix.c
rename to keyboards/lets_split/uno_slave/uno-matrix.c
diff --git a/keyboards/lets_split/uno-slave/uno-matrix.h b/keyboards/lets_split/uno_slave/uno-matrix.h
similarity index 100%
rename from keyboards/lets_split/uno-slave/uno-matrix.h
rename to keyboards/lets_split/uno_slave/uno-matrix.h