1 files changed, 295 insertions, 0 deletions

diff --git a/keyboards/mint60/serial.c b/keyboards/mint60/serial.c
new file mode 100644
index 000000000..591941587
--- /dev/null
+++ b/keyboards/mint60/serial.c
@@ -0,0 +1,295 @@
+/*
+ * 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"
+
+#ifdef USE_SERIAL
+
+#define _delay_sub_us(x)    __builtin_avr_delay_cycles(x)
+
+// Serial pulse period in microseconds.
+#define SELECT_SERIAL_SPEED 1
+#if SELECT_SERIAL_SPEED == 0
+  // Very High speed
+  #define SERIAL_DELAY 4             // micro sec
+  #define READ_WRITE_START_ADJUST 30 // cycles
+  #define READ_WRITE_WIDTH_ADJUST 10 // cycles
+#elif SELECT_SERIAL_SPEED == 1
+  // High speed
+  #define SERIAL_DELAY 6             // micro sec
+  #define READ_WRITE_START_ADJUST 23 // cycles
+  #define READ_WRITE_WIDTH_ADJUST 10 // cycles
+#elif SELECT_SERIAL_SPEED == 2
+  // Middle speed
+  #define SERIAL_DELAY 12            // micro sec
+  #define READ_WRITE_START_ADJUST 25 // cycles
+  #define READ_WRITE_WIDTH_ADJUST 10 // cycles
+#elif SELECT_SERIAL_SPEED == 3
+  // Low speed
+  #define SERIAL_DELAY 24            // micro sec
+  #define READ_WRITE_START_ADJUST 25 // cycles
+  #define READ_WRITE_WIDTH_ADJUST 10 // cycles
+#elif SELECT_SERIAL_SPEED == 4
+  // Very Low speed
+  #define SERIAL_DELAY 50            // micro sec
+  #define READ_WRITE_START_ADJUST 25 // cycles
+  #define READ_WRITE_WIDTH_ADJUST 10 // cycles
+#else
+#error Illegal Serial Speed
+#endif
+
+
+#define SERIAL_DELAY_HALF1 (SERIAL_DELAY/2)
+#define SERIAL_DELAY_HALF2 (SERIAL_DELAY - SERIAL_DELAY/2)
+
+#define SLAVE_INT_WIDTH 1
+#define SLAVE_INT_RESPONSE_TIME SERIAL_DELAY
+
+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_delay_half1(void) {
+  _delay_us(SERIAL_DELAY_HALF1);
+}
+
+inline static
+void serial_delay_half2(void) {
+  _delay_us(SERIAL_DELAY_HALF2);
+}
+
+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_with_pullup(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_with_pullup();
+
+#if SERIAL_PIN_MASK == _BV(PD0)
+  // Enable INT0
+  EIMSK |= _BV(INT0);
+  // Trigger on falling edge of INT0
+  EICRA &= ~(_BV(ISC00) | _BV(ISC01));
+#elif SERIAL_PIN_MASK == _BV(PD2)
+  // Enable INT2
+  EIMSK |= _BV(INT2);
+  // Trigger on falling edge of INT2
+  EICRA &= ~(_BV(ISC20) | _BV(ISC21));
+#else
+ #error unknown SERIAL_PIN_MASK value
+#endif
+}
+
+// Used by the sender to synchronize timing with the reciver.
+static
+void sync_recv(void) {
+  for (int i = 0; i < SERIAL_DELAY*5 && serial_read_pin(); i++ ) {
+  }
+  // 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());
+}
+
+// Used by the reciver to send a synchronization signal to the sender.
+static
+void sync_send(void) {
+  serial_low();
+  serial_delay();
+  serial_high();
+}
+
+// Reads a byte from the serial line
+static
+uint8_t serial_read_byte(void) {
+  uint8_t byte = 0;
+  _delay_sub_us(READ_WRITE_START_ADJUST);
+  for ( uint8_t i = 0; i < 8; ++i) {
+    serial_delay_half1();   // read the middle of pulses
+    byte = (byte << 1) | serial_read_pin();
+    _delay_sub_us(READ_WRITE_WIDTH_ADJUST);
+    serial_delay_half2();
+  }
+  return byte;
+}
+
+// Sends a byte with MSB ordering
+static
+void serial_write_byte(uint8_t data) {
+  uint8_t b = 1<<7;
+  while( b ) {
+    if(data & b) {
+      serial_high();
+    } else {
+      serial_low();
+    }
+    b >>= 1;
+    serial_delay();
+  }
+  serial_low(); // sync_send() / senc_recv() need raise edge
+}
+
+// interrupt handle to be used by the slave device
+ISR(SERIAL_PIN_INTERRUPT) {
+  serial_output();
+
+  // slave send phase
+  uint8_t checksum = 0;
+  for (int i = 0; i < SERIAL_SLAVE_BUFFER_LENGTH; ++i) {
+    sync_send();
+    serial_write_byte(serial_slave_buffer[i]);
+    checksum += serial_slave_buffer[i];
+  }
+  sync_send();
+  serial_write_byte(checksum);
+
+  // slave switch to input
+  sync_send(); //0
+  serial_delay_half1(); //1
+  serial_low();         //2
+  serial_input_with_pullup(); //2
+  serial_delay_half1(); //3
+
+  // slave recive phase
+  uint8_t checksum_computed = 0;
+  for (int i = 0; i < SERIAL_MASTER_BUFFER_LENGTH; ++i) {
+    sync_recv();
+    serial_master_buffer[i] = serial_read_byte();
+    checksum_computed += serial_master_buffer[i];
+  }
+  sync_recv();
+  uint8_t checksum_received = serial_read_byte();
+
+  if ( checksum_computed != checksum_received ) {
+    status |= SLAVE_DATA_CORRUPT;
+  } else {
+    status &= ~SLAVE_DATA_CORRUPT;
+  }
+
+  sync_recv(); //weit master output to high
+}
+
+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
+// 2 => checksum error
+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(SLAVE_INT_WIDTH);
+
+  // wait for the slaves response
+  serial_input_with_pullup();
+  _delay_us(SLAVE_INT_RESPONSE_TIME);
+
+  // check if the slave is present
+  if (serial_read_pin()) {
+    // slave failed to pull the line low, assume not present
+    serial_output();
+    serial_high();
+    sei();
+    return 1;
+  }
+
+  // master recive phase
+  // if the slave is present syncronize with it
+
+  uint8_t checksum_computed = 0;
+  // receive data from the slave
+  for (int i = 0; i < SERIAL_SLAVE_BUFFER_LENGTH; ++i) {
+    sync_recv();
+    serial_slave_buffer[i] = serial_read_byte();
+    checksum_computed += serial_slave_buffer[i];
+  }
+  sync_recv();
+  uint8_t checksum_received = serial_read_byte();
+
+  if (checksum_computed != checksum_received) {
+    serial_output();
+    serial_high();
+    sei();
+    return 2;
+  }
+
+  // master switch to output
+  sync_recv(); //0
+  serial_delay();  //1
+  serial_low();    //3
+  serial_output(); // 3
+  serial_delay_half1(); //4
+
+  // master send phase
+  uint8_t checksum = 0;
+
+  for (int i = 0; i < SERIAL_MASTER_BUFFER_LENGTH; ++i) {
+    sync_send();
+    serial_write_byte(serial_master_buffer[i]);
+    checksum += serial_master_buffer[i];
+  }
+  sync_send();
+  serial_write_byte(checksum);
+
+  // always, release the line when not in use
+  sync_send();
+
+  sei();
+  return 0;
+}
+
+#endif