code.c

The driver supports both the 16F and 18F families. The trick is that the driver carefully emulates t

////////////////////////////////////////////////////////////////////////////
// Serial Communications Test Program
//
// Exercises the serial driver code in <rs232_driver.h> by reading and
// writing to the serial port
////////////////////////////////////////////////////////////////////////////
// Author(s): Andrew Smallridge
// Date 17 November 2004
//
// Copyright (c) 2004-2005 Andrew Smallridge
// Copyright (c) 2004-2005 Pavel Baranov
// Copyright (c) 2004-2005 David Hobday
// Initialially developed on the PIC18F452
////////////////////////////////////////////////////////////////////////////
#pragma CLOCK_FREQ 20000000

#include <system.h>

////////////////////////////////////////////////////////////////////////////
//    The following three sections have been copied from the serial_driver.h file
//        USART software implementation template arguments and variables
//         USART hardwareware implementation template arguments
////////////////////////////////////////////////////////////////////////////
//
// **** START OF DEFAULTS USED FOR SOFTWARE USART EMULATION ****
//
// RAM used by the software USART driver to emulate the equivalent serial hardware registers
// Note this section is really just reserving the space. The defines in the subsequent section
// overlay these RAM locations                    
unsigned short sw_SPBRG@0x47;    // define location for the emulated SSPCON1
unsigned short sw_RCREG@0x48;    // define location for the emulated SSPCON2
unsigned short sw_TXREG@0x49;    // define location for the emulated SSPSTAT
unsigned short sw_TXSTA@0x4A;    // define location for the emulated SSPBUF
unsigned short sw_RCSTA@0x4B;    // define location for the emulated SSPADD
unsigned short sw_TXIF_PIR@0x4C;// define location for the emulated TXIF_PIR1
unsigned short sw_RCIF_PIR@0x4C;// define location for the emulated RCIF_PIR1

////////////////////////////////////////////////////////////////////////////
// USART software implementation template argument values
////////////////////////////////////////////////////////////////////////////
// variables cannot be passed as template arguments. The following constants map
// the PIC registers and software emulated USART RAM locations. These constants are
// then used by the templated functions. When changing the address of an emulated
// register the corresponding constant mapping must also be changed.
// PIC18F defaults for software emulated USART support
#define TX_PORT        0x06
#define TX_TRIS        0x86
#define TX_BIT        6
#define RX_PORT        0x06
#define RX_TRIS        0x86
#define RX_BIT        7
#define e_SPBRG        0x47
#define e_RCREG        0x48
#define e_TXREG        0x49
#define e_TXSTA        0x4A
#define e_RCSTA        0x4B
#define e_TXIF_PIR    0x4C
#define e_RCIF_PIR    0x4C
#define e_TXIF_BIT    4
#define e_RCIF_BIT    5                
#define MODE        (USART_reset_wdt)

////////////////////////////////////////////////////////////////////////////
// bit_time is used by the software emulated USART and is the number of CPU
// instruction cycles per bit.
//
// bit_time = FOSC / 4 / BAUDRATE
// The maximum value of bit_time currently limited to approximately 24000
// and is determined by the maximum word size supported by the compiler.
// this will change when 32 bit variables are supported.
// At FOSC of 40MHz the minimum standard baud rate is 600 baud.
// When using the software emulated USART functions ensure that the baud rate
// can be realistically supported by the FOSC used. bit_time values below
// 36 will likely lead to unreliable comms.
//
// The software UART takes 8 instruction cycles in a bit time loop. Therefore
// the driver software divides the bit_time value by 8. If experimenting with
// different values for bit_time use increments of 8 to guarentee a different
// bit time is selected
////////////////////////////////////////////////////////////////////////////

//#define bit_time 86    // 115200 baud at 40MHz
//#define bit_time 1041    // 9600 baud at 40MHz
#define bit_time 521    // 9600 baud at 20MHz

////////////////////////////////////////////////////////////////////////////
// Serial Control Flag Bits used for the MODE parameter
//
// DO NOT REMOVE THE COMMENTS FROM THE FOLLOWING FLAGS
// These flags are defined in serial_driver.h and are include here for information
// only. These flags are used in the MODE parameter.
//
// The USART_invert flag is used to signal the software UART that the serial
// input and output signals are inverted from normal RS232 communications.
// Hardware implementations that use standard RS232 transievers
// such as MS1488/MC1489 or MAX232 line drivers / receivers do NOT require this flag.
//
// The flags USART_HW and the USART_invert are mutually exclusive.
//
// Sample use: #define MODE (USART_reset_wdt | USART_HW)
//
////////////////////////////////////////////////////////////////////////////
// define USART Mode bits
//#define    USART_HW        0x01    // specifies use the HW USART in the PIC
//#define    USART_invert    0x02    // invert the tx and rx bits
//#define    USART_reset_wdt    0x04    // reset the WDT while waiting for a character in getc()


// **** END OF DEFAULTS USED FOR SOFTWARE USART EMULATION ****

#include <rs232_driver.h>

void main()
{
    // for the hardware UART the paramter passed is the divisor
    // the hardware usart enables dynamic reconfiguration of the baud rate
    // the software emulated USART baud rate is defined by constants in
    // serial_driver.h - this file alos contains the address mapping for
    // RAM required to support the software emulated USART

    uart_init(1,21);  // set high speed divisor mode and divisor value
    puts("Hello, world");
    while (1)
    {
        if (kbhit())
        {
            putc(getc());
        }
    }
}