text: /* $Id: autopilot_serial.h,v 1.2 2017/06/05 11:00:18 bouyer Exp $ */
  /*
   * Copyright (c) 2017 Manuel Bouyer
   *
   * All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in the
   *    documentation and/or other materials provided with the distribution.
   *
   * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
   * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
   * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
   * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
   * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
   * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
   * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
   * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
   * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
   * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   * POSSIBILITY OF SUCH DAMAGE.
   */
  
  char getchar(void);
  
  /* #define UART_BUFSIZE 16 */
  /* #define UART_BUFSIZE_MASK 0x0f */
  #define UART_BUFSIZE 128
  #define UART_BUFSIZE_MASK 0x7f
  
  extern char uart_txbuf[UART_BUFSIZE];
  extern unsigned char uart_txbuf_prod;
  extern volatile unsigned char uart_txbuf_cons;
  
  #define USART_INIT { \
  		uart_txbuf_prod = uart_txbuf_cons = 0; \
  	}
  
  #define USART_INTR {\
  	if (PIE3bits.TX2IE && PIR3bits.TX2IF) { \
  		if (uart_txbuf_prod == uart_txbuf_cons) { \
  			PIE3bits.TX2IE = 0; /* buffer empty */ \
  		} else { \
  			/* Place char in TXREG - this starts transmition */ \
  			TXREG2 = uart_txbuf[uart_txbuf_cons]; \
  			uart_txbuf_cons = (uart_txbuf_cons + 1) & UART_BUFSIZE_MASK;\
  		} \
  	} \
      }
  