9 files changed, 362 insertions, 2 deletions
diff --git a/keyboards/fc660c/README.md b/keyboards/fc660c/README.md
index ce84abad8..5cb9bcea4 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 000000000..5f4cb16f4
--- /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 000000000..f7066d92c
--- /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 0afd374a0..9771c8c03 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 f2a561767..da6ba9e74 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 000000000..084c890c4
--- /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 000000000..c15b6bc50
--- /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 211506fdf..69a96b979 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 883f7e657..c947947f8 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