/************************************************************************/
/*                                                                      */
/*  File:           avr/usi.c                                           */
/*  Description:    serial line device.                                 */
/*  Version:        1.0                                                 */
/*  Author:         Otto Mattik                                         */
/*                                                                      */
/*  (C)Copyright Otto Mattik 2014-2021.                                 */
/*                                                                      */
/*  This file is a part of 'armen' (a tiny operating system).           */
/*  'armen' is distributed under the CeCILL-V2.1 licence. For more      */
/*  details about this licence, please visit the website cecill.info    */
/*                                                                      */
/************************************************************************/

#ifndef AVR_UART_C
  #error "do not use this code directly, it must be included via avr_uart.c"
#endif

#ifdef USE_PWM
  #error "pwm and uart, used together, are incompatible"
#endif

/* TO DO: implement serial line via usi interface */

#include <avr/io.h>
#include <avr/interrupt.h>

/*
 * this code is based on the AVR307 publication.
 * it use the timer 1 (16 bits on ATtiny84, 8 bits on ATtiny85).
 * the uart is configured with 8 data bits, no parity and 1 stop bit.
 * the used pins are DI (input) and DO (output).
*/
#if defined(__AVR_ATtiny84__)

  #define USI_INPUT_PIN             PA6 /* receive */
  #define USI_OUTPUT_PIN            PA5 /* transmit */
  #define USI_CONFIG_PINS()         (\
                                     PORTA |= (1<<USI_INPUT_PIN),\
                                     DDRA = (DDRA\
                                       | (1<<USI_OUTPUT_PIN))\
                                       & ~(1<<USI_INPUT_PIN)\
                                    )
  #define USI_INPUT_START_BIT()     (PINA & (1<<USI_INPUT_PIN) ? 0 : 1)
  #define USI_CONFIG_TIMER(p)       (\
                                     TIMSK1 = 0, TCCR1A = 0,\
                                     TCCR1B = (1<<ICNC1) | (p)\
                                    )
  #define USI_CONFIG_DEVICE()       ()

  #define USI_INPUT_CAPTURE_INT     PCINT6_vect

#elif defined(__AVR_ATtiny85__)

  #define USI_INPUT_PIN             PB0 /* receive */
  #define USI_OUTPUT_PIN            PB1 /* transmit */
  #define USI_CONFIG_PINS()         (\
                                     PORTB |= (1<<USI_INPUT_PIN),\
                                     DDRB = (DDRB\
                                       | (1<<USI_OUTPUT_PIN))\
                                       & ~(1<<USI_INPUT_PIN)\
                                    )
  #define USI_INPUT_START_BIT()     (PINB & (1<<USI_INPUT_PIN) ? 0 : 1)
  #define USI_CONFIG_TIMER(p)       (TIMSK = 0, TCCR1 = (p))
  #define USI_CONFIG_DEVICE()       ()

  #define USI_INPUT_CAPTURE_INT     PCINT0_vect

#else
  #error "no or unavailable cpu defined"
#endif

#define USI_OVERFLOW_INTERRUPT      USI_OVF_vect
#define TIMER_OVERFLOW_INTERRUPT    TIMER1_OVF_vect

#define CONFIG_RS485(p)             (CONFIG_RS485_DRIVER(), \
                                     CONFIG_TIMER_PRESCALE(p), \
                                     CONFIG_USI_DEVICE())

#define USI_RX_BUFFER_SIZE          16
#define UART_ECHOO_CHECK            0x40

/*
 * reverse bits order lsb<->msb
 *
 * input:
 *  byte        byte to reverse
 * output:
 *  reversed byte
*/
static uint8_t reverse_byte( uint8_t byte )
{
   byte = ((byte >> 1) & 0x55) | ((byte << 1) & 0xaa);
   byte = ((byte >> 2) & 0x33) | ((byte << 2) & 0xcc);
   byte = ((byte >> 4) & 0x0f) | ((byte << 4) & 0xf0);
   return( byte );
}

/*
 * initialize device
 *
 * input:
 *  device      identifier (always 0)
 *  config      uart configuration
 * output:
 *  0 if success, otherwise -1
*/
static int8_t uart_open( uint8_t device, uint8_t config )
{
    return( -1 );
}

/*
 * release device
 *
 * input:
 *  device      identifier
 * output:
 *  0 if success, otherwise -1
*/
static int8_t uart_close( uint8_t device )
{
    return( -1 );
}

/*
 * read from device
 *
 * input:
 *  device      identifier (always 0)
 *  byte        address of byte to read
 * output:
 *  0 if success, otherwise -1
*/
static int8_t uart_read( uint8_t device, uint8_t* byte )
{
    return( -1 );
}

/*
 * write to device
 *
 * input:
 *  device      identifier (always 0)
 *  byte        byte to write
 * output:
 *  0 if success, otherwise -1
*/
static int8_t uart_write( uint8_t device, uint8_t byte )
{
    return( -1 );
}

/*
 * device special feature
 *
 * input:
 *  device      identifier (always 0)
 *  request     device dependent
 *  args        list of arguments
 * output:
 *  0 if success, otherwise -1
*/
#ifdef UART_IOCTL
static int8_t uart_ioctl( uint8_t device, uint8_t request, va_list args )
{
    return( -1 );
}
#endif