actuation point adjustment for fc980c and fc660c (#2134)

* add i2c lib submodule

* add actuation point adjustment to fc980c

* add actuation point adjustment to fc660c also.

* use https for i2c submodule

* move to existing i2c lib

* properly remove old submodule

* oops, forgot some files for the fc660c

22 files changed, 850 insertions, 4 deletions

diff --git a/keyboards/fc660c/README.md b/keyboards/fc660c/README.md
index ce84abad83..5cb9bcea48 100644
--- a/keyboards/fc660c/README.md
+++ b/keyboards/fc660c/README.md
@@ -25,6 +25,17 @@ Thread on Geekhack: https://geekhack.org/index.php?topic=88439.0
 
 Also: https://geekhack.org/index.php?topic=88720.0
 
+
+Actuation Point adjustment
+--------------------------
+You can adjust the actuation point of the keys by setting `ACTUATION_DEPTH_ADJUSTMENT` in `config.h`.
+A value above 0 will result in a deeper, less sensitive actuation whereas a value above 1 will result in a more shallow, more sensitive actuation.
+Be careful with this setting and use small values (+/-5).
+See the `actuation-point-example` keymap of the `fc980c` keyboard for an example.
+For more information, inspect the `fc660c_i2c` branch of TMK [here](https://github.com/tmk/tmk_keyboard/tree/fc660c_i2c).
+Functionality for writing to the EEPROM has deliberately not been included to reduce the chance of people messing up their boards.
+
+
 Pinouts
 -------
 
diff --git a/keyboards/fc660c/actuation_point.c b/keyboards/fc660c/actuation_point.c
new file mode 100644
index 0000000000..5f4cb16f40
--- /dev/null
+++ b/keyboards/fc660c/actuation_point.c
@@ -0,0 +1,87 @@
+/*
+Copyright 2017 Balz Guenat
+based on work by Jun Wako <wakojun@gmail.com>
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 2 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "actuation_point.h"
+#include "i2c.h"
+
+///////////////////////////////////////////////////////////////////////////////
+//
+// AD5258 I2C digital potentiometer
+// http://www.analog.com/media/en/technical-documentation/data-sheets/AD5258.pdf
+//
+#define AD5258_ADDR 0b0011000
+#define AD5258_INST_RDAC        0x00
+#define AD5258_INST_EEPROM      0x20
+
+uint8_t read_rdac(void) {
+    // read RDAC register
+    i2c_start_write(AD5258_ADDR);
+    i2c_master_write(AD5258_INST_RDAC);
+    i2c_start_read(AD5258_ADDR);
+    uint8_t ret = i2c_master_read(I2C_NACK);
+    i2c_master_stop();
+    return ret;
+};
+
+uint8_t read_eeprom(void) {
+    i2c_start_write(AD5258_ADDR);
+    i2c_master_write(AD5258_INST_EEPROM);
+    i2c_start_read(AD5258_ADDR);
+    uint8_t ret = i2c_master_read(I2C_NACK);
+    i2c_master_stop();
+    return ret;
+};
+
+void write_rdac(uint8_t rdac) {
+    // write RDAC register:
+    i2c_start_write(AD5258_ADDR);
+    i2c_master_write(AD5258_INST_RDAC);
+    i2c_master_write(rdac & 0x3F);
+    i2c_master_stop();
+};
+
+void actuation_point_up(void) {
+    // write RDAC register: lower value makes actuation point shallow
+    uint8_t rdac = read_rdac();
+    if (rdac == 0)
+        write_rdac(0);
+    else
+        write_rdac(rdac-1);
+};
+
+void actuation_point_down(void) {
+    // write RDAC register: higher value makes actuation point deep
+    uint8_t rdac = read_rdac();
+    if (rdac == 63)
+        write_rdac(63);
+    else
+        write_rdac(rdac+1);
+};
+
+void adjust_actuation_point(int offset) {
+    i2c_master_init();
+    uint8_t rdac = read_eeprom() + offset;
+    if (rdac > 63) { // protects from under and overflows
+        if (offset > 0)
+            write_rdac(63);
+        else
+            write_rdac(0);
+    } else {
+        write_rdac(rdac);
+    }
+}
diff --git a/keyboards/fc660c/actuation_point.h b/keyboards/fc660c/actuation_point.h
new file mode 100644
index 0000000000..f7066d92c1
--- /dev/null
+++ b/keyboards/fc660c/actuation_point.h
@@ -0,0 +1,32 @@
+/*
+Copyright 2017 Balz Guenat
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 2 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef ACTUATION_POINT_H
+#define ACTUATION_POINT_H
+
+#include <stdint.h>
+
+// see keymaps/actuation-point-example to see how these functions can be used.
+uint8_t read_rdac(void);
+uint8_t read_eeprom(void);
+void actuation_point_up(void);
+void actuation_point_down(void);
+
+// be careful with this.
+void adjust_actuation_point(int offset);
+
+#endif
diff --git a/keyboards/fc660c/config.h b/keyboards/fc660c/config.h
index 0afd374a0c..9771c8c03d 100644
--- a/keyboards/fc660c/config.h
+++ b/keyboards/fc660c/config.h
@@ -64,6 +64,8 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
  *  These options are also useful to firmware size reduction.
  */
 
+#define USE_I2C
+
 /* disable debug print */
 //#define NO_DEBUG
 
@@ -77,4 +79,11 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 //#define NO_ACTION_MACRO
 //#define NO_ACTION_FUNCTION
 
+// higher value means deeper actuation point, less sensitive
+// be careful and only make small adjustments (steps of 1 or 2).
+// too high and keys will fail to actuate. too low and keys will actuate spontaneously.
+// test all keys before further adjustment.
+// this should probably stay in the range +/-5.
+// #define ACTUATION_DEPTH_ADJUSTMENT 0
+
 #endif
diff --git a/keyboards/fc660c/fc660c.c b/keyboards/fc660c/fc660c.c
index f2a5617672..da6ba9e744 100644
--- a/keyboards/fc660c/fc660c.c
+++ b/keyboards/fc660c/fc660c.c
@@ -16,10 +16,18 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 #include "fc660c.h"
 
+#ifdef ACTUATION_DEPTH_ADJUSTMENT
+#include "actuation_point.h"
+#endif
+
 void matrix_init_kb(void) {
 	// put your keyboard start-up code here
 	// runs once when the firmware starts up
 
+#ifdef ACTUATION_DEPTH_ADJUSTMENT
+    adjust_actuation_point(ACTUATION_DEPTH_ADJUSTMENT);
+#endif
+
 	matrix_init_user();
 }
 
diff --git a/keyboards/fc660c/i2c.c b/keyboards/fc660c/i2c.c
new file mode 100644
index 0000000000..084c890c40
--- /dev/null
+++ b/keyboards/fc660c/i2c.c
@@ -0,0 +1,162 @@
+#include <util/twi.h>
+#include <avr/io.h>
+#include <stdlib.h>
+#include <avr/interrupt.h>
+#include <util/twi.h>
+#include <stdbool.h>
+#include "i2c.h"
+
+#ifdef USE_I2C
+
+// Limits the amount of we wait for any one i2c transaction.
+// Since were running SCL line 100kHz (=> 10μs/bit), and each transactions is
+// 9 bits, a single transaction will take around 90μs to complete.
+//
+// (F_CPU/SCL_CLOCK)  =>  # of μC cycles to transfer a bit
+// poll loop takes at least 8 clock cycles to execute
+#define I2C_LOOP_TIMEOUT (9+1)*(F_CPU/SCL_CLOCK)/8
+
+#define BUFFER_POS_INC() (slave_buffer_pos = (slave_buffer_pos+1)%SLAVE_BUFFER_SIZE)
+
+volatile uint8_t i2c_slave_buffer[SLAVE_BUFFER_SIZE];
+
+static volatile uint8_t slave_buffer_pos;
+static volatile bool slave_has_register_set = false;
+
+// Wait for an i2c operation to finish
+inline static
+void i2c_delay(void) {
+  uint16_t lim = 0;
+  while(!(TWCR & (1<<TWINT)) && lim < I2C_LOOP_TIMEOUT)
+    lim++;
+
+  // easier way, but will wait slightly longer
+  // _delay_us(100);
+}
+
+// Setup twi to run at 100kHz
+void i2c_master_init(void) {
+  // no prescaler
+  TWSR = 0;
+  // Set TWI clock frequency to SCL_CLOCK. Need TWBR>10.
+  // Check datasheets for more info.
+  TWBR = ((F_CPU/SCL_CLOCK)-16)/2;
+}
+
+// Start a transaction with the given i2c slave address. The direction of the
+// transfer is set with I2C_READ and I2C_WRITE.
+// returns: 0 => success
+//          1 => error
+uint8_t i2c_master_start(uint8_t address) {
+  TWCR = (1<<TWINT) | (1<<TWEN) | (1<<TWSTA);
+
+  i2c_delay();
+
+  // check that we started successfully
+  if ( (TW_STATUS != TW_START) && (TW_STATUS != TW_REP_START))
+    return 1;
+
+  TWDR = address;
+  TWCR = (1<<TWINT) | (1<<TWEN);
+
+  i2c_delay();
+
+  if ( (TW_STATUS != TW_MT_SLA_ACK) && (TW_STATUS != TW_MR_SLA_ACK) )
+    return 1; // slave did not acknowledge
+  else
+    return 0; // success
+}
+
+
+// Finish the i2c transaction.
+void i2c_master_stop(void) {
+  TWCR = (1<<TWINT) | (1<<TWEN) | (1<<TWSTO);
+
+  uint16_t lim = 0;
+  while(!(TWCR & (1<<TWSTO)) && lim < I2C_LOOP_TIMEOUT)
+    lim++;
+}
+
+// Write one byte to the i2c slave.
+// returns 0 => slave ACK
+//         1 => slave NACK
+uint8_t i2c_master_write(uint8_t data) {
+  TWDR = data;
+  TWCR = (1<<TWINT) | (1<<TWEN);
+
+  i2c_delay();
+
+  // check if the slave acknowledged us
+  return (TW_STATUS == TW_MT_DATA_ACK) ? 0 : 1;
+}
+
+// Read one byte from the i2c slave. If ack=1 the slave is acknowledged,
+// if ack=0 the acknowledge bit is not set.
+// returns: byte read from i2c device
+uint8_t i2c_master_read(int ack) {
+  TWCR = (1<<TWINT) | (1<<TWEN) | (ack<<TWEA);
+
+  i2c_delay();
+  return TWDR;
+}
+
+void i2c_reset_state(void) {
+  TWCR = 0;
+}
+
+void i2c_slave_init(uint8_t address) {
+  TWAR = address << 0; // slave i2c address
+  // TWEN  - twi enable
+  // TWEA  - enable address acknowledgement
+  // TWINT - twi interrupt flag
+  // TWIE  - enable the twi interrupt
+  TWCR = (1<<TWIE) | (1<<TWEA) | (1<<TWINT) | (1<<TWEN);
+}
+
+ISR(TWI_vect);
+
+ISR(TWI_vect) {
+  uint8_t ack = 1;
+  switch(TW_STATUS) {
+    case TW_SR_SLA_ACK:
+      // this device has been addressed as a slave receiver
+      slave_has_register_set = false;
+      break;
+
+    case TW_SR_DATA_ACK:
+      // this device has received data as a slave receiver
+      // The first byte that we receive in this transaction sets the location
+      // of the read/write location of the slaves memory that it exposes over
+      // i2c.  After that, bytes will be written at slave_buffer_pos, incrementing
+      // slave_buffer_pos after each write.
+      if(!slave_has_register_set) {
+        slave_buffer_pos = TWDR;
+        // don't acknowledge the master if this memory loctaion is out of bounds
+        if ( slave_buffer_pos >= SLAVE_BUFFER_SIZE ) {
+          ack = 0;
+          slave_buffer_pos = 0;
+        }
+        slave_has_register_set = true;
+      } else {
+        i2c_slave_buffer[slave_buffer_pos] = TWDR;
+        BUFFER_POS_INC();
+      }
+      break;
+
+    case TW_ST_SLA_ACK:
+    case TW_ST_DATA_ACK:
+      // master has addressed this device as a slave transmitter and is
+      // requesting data.
+      TWDR = i2c_slave_buffer[slave_buffer_pos];
+      BUFFER_POS_INC();
+      break;
+
+    case TW_BUS_ERROR: // something went wrong, reset twi state
+      TWCR = 0;
+    default:
+      break;
+  }
+  // Reset everything, so we are ready for the next TWI interrupt
+  TWCR |= (1<<TWIE) | (1<<TWINT) | (ack<<TWEA) | (1<<TWEN);
+}
+#endif
diff --git a/keyboards/fc660c/i2c.h b/keyboards/fc660c/i2c.h
new file mode 100644
index 0000000000..c15b6bc506
--- /dev/null
+++ b/keyboards/fc660c/i2c.h
@@ -0,0 +1,49 @@
+#ifndef I2C_H
+#define I2C_H
+
+#include <stdint.h>
+
+#ifndef F_CPU
+#define F_CPU 16000000UL
+#endif
+
+#define I2C_READ 1
+#define I2C_WRITE 0
+
+#define I2C_ACK 1
+#define I2C_NACK 0
+
+#define SLAVE_BUFFER_SIZE 0x10
+
+// i2c SCL clock frequency
+#define SCL_CLOCK  400000L
+
+extern volatile uint8_t i2c_slave_buffer[SLAVE_BUFFER_SIZE];
+
+void i2c_master_init(void);
+uint8_t i2c_master_start(uint8_t address);
+void i2c_master_stop(void);
+uint8_t i2c_master_write(uint8_t data);
+uint8_t i2c_master_read(int);
+void i2c_reset_state(void);
+void i2c_slave_init(uint8_t address);
+
+
+static inline unsigned char i2c_start_read(unsigned char addr) {
+  return i2c_master_start((addr << 1) | I2C_READ);
+}
+
+static inline unsigned char i2c_start_write(unsigned char addr) {
+  return i2c_master_start((addr << 1) | I2C_WRITE);
+}
+
+// from SSD1306 scrips
+extern unsigned char i2c_rep_start(unsigned char addr);
+extern void i2c_start_wait(unsigned char addr);
+extern unsigned char i2c_readAck(void);
+extern unsigned char i2c_readNak(void);
+extern unsigned char i2c_read(unsigned char ack);
+
+#define i2c_read(ack)  (ack) ? i2c_readAck() : i2c_readNak();
+
+#endif
diff --git a/keyboards/fc660c/matrix.c b/keyboards/fc660c/matrix.c
index 211506fdf3..69a96b9792 100644
--- a/keyboards/fc660c/matrix.c
+++ b/keyboards/fc660c/matrix.c
@@ -21,7 +21,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 #include <stdint.h>
 #include <stdbool.h>
-#include <util/delay.h>
+#include "wait.h"
 #include "print.h"
 #include "debug.h"
 #include "util.h"
diff --git a/keyboards/fc660c/rules.mk b/keyboards/fc660c/rules.mk
index 883f7e657c..c947947f80 100644
--- a/keyboards/fc660c/rules.mk
+++ b/keyboards/fc660c/rules.mk
@@ -61,4 +61,6 @@ NKRO_ENABLE ?= yes		# USB Nkey Rollover - not yet supported in LUFA
 #EXTRALDFLAGS = -Wl,--relax
 
 CUSTOM_MATRIX = yes
-SRC += matrix.c
+SRC +=	matrix.c \
+		actuation_point.c \
+		i2c.c
diff --git a/keyboards/fc980c/README.md b/keyboards/fc980c/README.md
index 7e44436efc..10d84a0961 100644
--- a/keyboards/fc980c/README.md
+++ b/keyboards/fc980c/README.md
@@ -32,6 +32,16 @@ The keyboard is very similar electronically to its sibling model FC660C you can
 FC660C Alt Controller: https://geekhack.org/index.php?topic=88439.0
 
 
+Actuation Point adjustment
+--------------------------
+You can adjust the actuation point of the keys by setting `ACTUATION_DEPTH_ADJUSTMENT` in `config.h`.
+A value above 0 will result in a deeper, less sensitive actuation whereas a value above 1 will result in a more shallow, more sensitive actuation.
+Be careful with this setting and use small values (+/-5).
+See the `actuation-point-example` keymap for an example.
+For more information, inspect the `fc660c_i2c` branch of TMK [here](https://github.com/tmk/tmk_keyboard/tree/fc660c_i2c).
+Functionality for writing to the EEPROM has deliberately not been included to reduce the chance of people messing up their boards.
+
+
 Hardware
 --------
 This project uses common and familiar ATmega32u4 but any microcontroller with 5V I/O will work.
diff --git a/keyboards/fc980c/actuation_point.c b/keyboards/fc980c/actuation_point.c
new file mode 100644
index 0000000000..5f4cb16f40
--- /dev/null
+++ b/keyboards/fc980c/actuation_point.c
@@ -0,0 +1,87 @@
+/*
+Copyright 2017 Balz Guenat
+based on work by Jun Wako <wakojun@gmail.com>
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 2 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "actuation_point.h"
+#include "i2c.h"
+
+///////////////////////////////////////////////////////////////////////////////
+//
+// AD5258 I2C digital potentiometer
+// http://www.analog.com/media/en/technical-documentation/data-sheets/AD5258.pdf
+//
+#define AD5258_ADDR 0b0011000
+#define AD5258_INST_RDAC        0x00
+#define AD5258_INST_EEPROM      0x20
+
+uint8_t read_rdac(void) {
+    // read RDAC register
+    i2c_start_write(AD5258_ADDR);
+    i2c_master_write(AD5258_INST_RDAC);
+    i2c_start_read(AD5258_ADDR);
+    uint8_t ret = i2c_master_read(I2C_NACK);
+    i2c_master_stop();
+    return ret;
+};
+
+uint8_t read_eeprom(void) {
+    i2c_start_write(AD5258_ADDR);
+    i2c_master_write(AD5258_INST_EEPROM);
+    i2c_start_read(AD5258_ADDR);
+    uint8_t ret = i2c_master_read(I2C_NACK);
+    i2c_master_stop();
+    return ret;
+};
+
+void write_rdac(uint8_t rdac) {
+    // write RDAC register:
+    i2c_start_write(AD5258_ADDR);
+    i2c_master_write(AD5258_INST_RDAC);
+    i2c_master_write(rdac & 0x3F);
+    i2c_master_stop();
+};
+
+void actuation_point_up(void) {
+    // write RDAC register: lower value makes actuation point shallow
+    uint8_t rdac = read_rdac();
+    if (rdac == 0)
+        write_rdac(0);
+    else
+        write_rdac(rdac-1);
+};
+
+void actuation_point_down(void) {
+    // write RDAC register: higher value makes actuation point deep
+    uint8_t rdac = read_rdac();
+    if (rdac == 63)
+        write_rdac(63);
+    else
+        write_rdac(rdac+1);
+};
+
+void adjust_actuation_point(int offset) {
+    i2c_master_init();
+    uint8_t rdac = read_eeprom() + offset;
+    if (rdac > 63) { // protects from under and overflows
+        if (offset > 0)
+            write_rdac(63);
+        else
+            write_rdac(0);
+    } else {
+        write_rdac(rdac);
+    }
+}
diff --git a/keyboards/fc980c/actuation_point.h b/keyboards/fc980c/actuation_point.h
new file mode 100644
index 0000000000..f7066d92c1
--- /dev/null
+++ b/keyboards/fc980c/actuation_point.h
@@ -0,0 +1,32 @@
+/*
+Copyright 2017 Balz Guenat
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 2 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef ACTUATION_POINT_H
+#define ACTUATION_POINT_H
+
+#include <stdint.h>
+
+// see keymaps/actuation-point-example to see how these functions can be used.
+uint8_t read_rdac(void);
+uint8_t read_eeprom(void);
+void actuation_point_up(void);
+void actuation_point_down(void);
+
+// be careful with this.
+void adjust_actuation_point(int offset);
+
+#endif
diff --git a/keyboards/fc980c/config.h b/keyboards/fc980c/config.h
index a79f6f57b3..1b1f41c909 100644
--- a/keyboards/fc980c/config.h
+++ b/keyboards/fc980c/config.h
@@ -68,6 +68,8 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
  *  These options are also useful to firmware size reduction.
  */
 
+#define USE_I2C
+
 /* disable debug print */
 //#define NO_DEBUG
 
@@ -81,4 +83,11 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 //#define NO_ACTION_MACRO
 //#define NO_ACTION_FUNCTION
 
+// higher value means deeper actuation point, less sensitive
+// be careful and only make small adjustments (steps of 1 or 2).
+// too high and keys will fail to actuate. too low and keys will actuate spontaneously.
+// test all keys before further adjustment.
+// this should probably stay in the range +/-5.
+// #define ACTUATION_DEPTH_ADJUSTMENT 0
+
 #endif
diff --git a/keyboards/fc980c/fc980c.c b/keyboards/fc980c/fc980c.c
index b782431054..c09eacfa33 100644
--- a/keyboards/fc980c/fc980c.c
+++ b/keyboards/fc980c/fc980c.c
@@ -14,12 +14,21 @@ GNU General Public License for more details.
 You should have received a copy of the GNU General Public License
 along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
+
 #include "fc980c.h"
 
+#ifdef ACTUATION_DEPTH_ADJUSTMENT
+#include "actuation_point.h"
+#endif
+
 void matrix_init_kb(void) {
 	// put your keyboard start-up code here
 	// runs once when the firmware starts up
 
+#ifdef ACTUATION_DEPTH_ADJUSTMENT
+    adjust_actuation_point(ACTUATION_DEPTH_ADJUSTMENT);
+#endif
+
 	matrix_init_user();
 }
 
diff --git a/keyboards/fc980c/i2c.c b/keyboards/fc980c/i2c.c
new file mode 100644
index 0000000000..084c890c40
--- /dev/null
+++ b/keyboards/fc980c/i2c.c
@@ -0,0 +1,162 @@
+#include <util/twi.h>
+#include <avr/io.h>
+#include <stdlib.h>
+#include <avr/interrupt.h>
+#include <util/twi.h>
+#include <stdbool.h>
+#include "i2c.h"
+
+#ifdef USE_I2C
+
+// Limits the amount of we wait for any one i2c transaction.
+// Since were running SCL line 100kHz (=> 10μs/bit), and each transactions is
+// 9 bits, a single transaction will take around 90μs to complete.
+//
+// (F_CPU/SCL_CLOCK)  =>  # of μC cycles to transfer a bit
+// poll loop takes at least 8 clock cycles to execute
+#define I2C_LOOP_TIMEOUT (9+1)*(F_CPU/SCL_CLOCK)/8
+
+#define BUFFER_POS_INC() (slave_buffer_pos = (slave_buffer_pos+1)%SLAVE_BUFFER_SIZE)
+
+volatile uint8_t i2c_slave_buffer[SLAVE_BUFFER_SIZE];
+
+static volatile uint8_t slave_buffer_pos;
+static volatile bool slave_has_register_set = false;
+
+// Wait for an i2c operation to finish
+inline static
+void i2c_delay(void) {
+  uint16_t lim = 0;
+  while(!(TWCR & (1<<TWINT)) && lim < I2C_LOOP_TIMEOUT)
+    lim++;
+
+  // easier way, but will wait slightly longer
+  // _delay_us(100);
+}
+
+// Setup twi to run at 100kHz
+void i2c_master_init(void) {
+  // no prescaler
+  TWSR = 0;
+  // Set TWI clock frequency to SCL_CLOCK. Need TWBR>10.
+  // Check datasheets for more info.
+  TWBR = ((F_CPU/SCL_CLOCK)-16)/2;
+}
+
+// Start a transaction with the given i2c slave address. The direction of the
+// transfer is set with I2C_READ and I2C_WRITE.
+// returns: 0 => success
+//          1 => error
+uint8_t i2c_master_start(uint8_t address) {
+  TWCR = (1<<TWINT) | (1<<TWEN) | (1<<TWSTA);
+
+  i2c_delay();
+
+  // check that we started successfully
+  if ( (TW_STATUS != TW_START) && (TW_STATUS != TW_REP_START))
+    return 1;
+
+  TWDR = address;
+  TWCR = (1<<TWINT) | (1<<TWEN);
+
+  i2c_delay();
+
+  if ( (TW_STATUS != TW_MT_SLA_ACK) && (TW_STATUS != TW_MR_SLA_ACK) )
+    return 1; // slave did not acknowledge
+  else
+    return 0; // success
+}
+
+
+// Finish the i2c transaction.
+void i2c_master_stop(void) {
+  TWCR = (1<<TWINT) | (1<<TWEN) | (1<<TWSTO);
+
+  uint16_t lim = 0;
+  while(!(TWCR & (1<<TWSTO)) && lim < I2C_LOOP_TIMEOUT)
+    lim++;
+}
+
+// Write one byte to the i2c slave.
+// returns 0 => slave ACK
+//         1 => slave NACK
+uint8_t i2c_master_write(uint8_t data) {
+  TWDR = data;
+  TWCR = (1<<TWINT) | (1<<TWEN);
+
+  i2c_delay();
+
+  // check if the slave acknowledged us
+  return (TW_STATUS == TW_MT_DATA_ACK) ? 0 : 1;
+}
+
+// Read one byte from the i2c slave. If ack=1 the slave is acknowledged,
+// if ack=0 the acknowledge bit is not set.
+// returns: byte read from i2c device
+uint8_t i2c_master_read(int ack) {
+  TWCR = (1<<TWINT) | (1<<TWEN) | (ack<<TWEA);
+
+  i2c_delay();
+  return TWDR;
+}
+
+void i2c_reset_state(void) {
+  TWCR = 0;
+}
+
+void i2c_slave_init(uint8_t address) {
+  TWAR = address << 0; // slave i2c address
+  // TWEN  - twi enable
+  // TWEA  - enable address acknowledgement
+  // TWINT - twi interrupt flag
+  // TWIE  - enable the twi interrupt
+  TWCR = (1<<TWIE) | (1<<TWEA) | (1<<TWINT) | (1<<TWEN);
+}
+
+ISR(TWI_vect);
+
+ISR(TWI_vect) {
+  uint8_t ack = 1;
+  switch(TW_STATUS) {
+    case TW_SR_SLA_ACK:
+      // this device has been addressed as a slave receiver
+      slave_has_register_set = false;
+      break;
+
+    case TW_SR_DATA_ACK:
+      // this device has received data as a slave receiver
+      // The first byte that we receive in this transaction sets the location
+      // of the read/write location of the slaves memory that it exposes over
+      // i2c.  After that, bytes will be written at slave_buffer_pos, incrementing
+      // slave_buffer_pos after each write.
+      if(!slave_has_register_set) {
+        slave_buffer_pos = TWDR;
+        // don't acknowledge the master if this memory loctaion is out of bounds
+        if ( slave_buffer_pos >= SLAVE_BUFFER_SIZE ) {
+          ack = 0;
+          slave_buffer_pos = 0;
+        }
+        slave_has_register_set = true;
+      } else {
+        i2c_slave_buffer[slave_buffer_pos] = TWDR;
+        BUFFER_POS_INC();
+      }
+      break;
+
+    case TW_ST_SLA_ACK:
+    case TW_ST_DATA_ACK:
+      // master has addressed this device as a slave transmitter and is
+      // requesting data.
+      TWDR = i2c_slave_buffer[slave_buffer_pos];
+      BUFFER_POS_INC();
+      break;
+
+    case TW_BUS_ERROR: // something went wrong, reset twi state
+      TWCR = 0;
+    default:
+      break;
+  }
+  // Reset everything, so we are ready for the next TWI interrupt
+  TWCR |= (1<<TWIE) | (1<<TWINT) | (ack<<TWEA) | (1<<TWEN);
+}
+#endif
diff --git a/keyboards/fc980c/i2c.h b/keyboards/fc980c/i2c.h
new file mode 100644
index 0000000000..c15b6bc506
--- /dev/null
+++ b/keyboards/fc980c/i2c.h
@@ -0,0 +1,49 @@
+#ifndef I2C_H
+#define I2C_H
+
+#include <stdint.h>
+
+#ifndef F_CPU
+#define F_CPU 16000000UL
+#endif
+
+#define I2C_READ 1
+#define I2C_WRITE 0
+
+#define I2C_ACK 1
+#define I2C_NACK 0
+
+#define SLAVE_BUFFER_SIZE 0x10
+
+// i2c SCL clock frequency
+#define SCL_CLOCK  400000L
+
+extern volatile uint8_t i2c_slave_buffer[SLAVE_BUFFER_SIZE];
+
+void i2c_master_init(void);
+uint8_t i2c_master_start(uint8_t address);
+void i2c_master_stop(void);
+uint8_t i2c_master_write(uint8_t data);
+uint8_t i2c_master_read(int);
+void i2c_reset_state(void);
+void i2c_slave_init(uint8_t address);
+
+
+static inline unsigned char i2c_start_read(unsigned char addr) {
+  return i2c_master_start((addr << 1) | I2C_READ);
+}
+
+static inline unsigned char i2c_start_write(unsigned char addr) {
+  return i2c_master_start((addr << 1) | I2C_WRITE);
+}
+
+// from SSD1306 scrips
+extern unsigned char i2c_rep_start(unsigned char addr);
+extern void i2c_start_wait(unsigned char addr);
+extern unsigned char i2c_readAck(void);
+extern unsigned char i2c_readNak(void);
+extern unsigned char i2c_read(unsigned char ack);
+
+#define i2c_read(ack)  (ack) ? i2c_readAck() : i2c_readNak();
+
+#endif
diff --git a/keyboards/fc980c/keymaps/actuation-point-example/README.md b/keyboards/fc980c/keymaps/actuation-point-example/README.md
new file mode 100644
index 0000000000..e4e9ab98ca
--- /dev/null
+++ b/keyboards/fc980c/keymaps/actuation-point-example/README.md
@@ -0,0 +1,9 @@
+# Actuation Point adjustment example keymap
+
+This keymap is an example of how the actuation point adjustment functionality could be used. In `config.h`, we set `ACTUATION_DEPTH_ADJUSTMENT` to `+1`, which puts the actuation point slightly deeper, making the keys less sensitive.
+
+If [hid_listen](https://www.pjrc.com/teensy/hid_listen.html) is running, `CAPS_LOCK + F9` prints the current RDAC setting and `CAPS_LOCK + F10` prints the default or base setting. `CAPS_LOCK + F11` and `CAPS_LOCK + F12` can be used to adjust the actuation point dynamically. Make only small adjustments and find your ideal setting. For example, if the base setting of your keyboard is 56 but you prefer a slightly lower actuation point at 58, you should set `ACTUATION_DEPTH_ADJUSTMENT` to `+2`.
+
+If something goes wrong during adjustment, for example keys not actuating anymore or actuating spontaneously, don't panic. Just unplug the keyboard and plug it back in. This will revert all your dynamic changes made with `F11` and `F12`.
+
+If you discover you have set a too high or low value for `ACTUATION_DEPTH_ADJUSTMENT`, you will need to recompile and reflash your keyboard.
diff --git a/keyboards/fc980c/keymaps/actuation-point-example/config.h b/keyboards/fc980c/keymaps/actuation-point-example/config.h
new file mode 100644
index 0000000000..6c9893f422
--- /dev/null
+++ b/keyboards/fc980c/keymaps/actuation-point-example/config.h
@@ -0,0 +1,32 @@
+/* Copyright 2017 Balz Guenat
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation