/*	PIC serial port test
	http://www.captain.at/electronics/

	Sends back any character received via the serial port
	Use with "ser":
	
	# ./ser
	baud=9600
	baud=9600
	written:ABC
	readport=ABC
	#
	
	Compile with CC5x: http://www.bknd.com/cc5x/
	c:\picc\cc5x mmc.c -Ic:\picc\ -ammc.ASM -u
	
	CC5x runs nicely on Linux with "dosemu" http://www.dosemu.org/

	Credit:
	Ported from assembler source of "The Tekatch-Welch Magnetometer"
	http://crocus.physics.mcmaster.ca/Magnetometer/TW/
*/
#include <16F876.h>
#include "int16CXX.H"

#define CP_off  |= 0x3F30
#define LVP |= 128
#pragma config CP_off,PWRTE=on,WDTE=off,FOSC=HS,BODEN=on,LVP

#pragma origin 4		// Der folgende Code steht ab Adresse 4

interrupt myInterrupt(void)		// interrupt service routine at address 4
{
	int_save_registers
	char rec;
	if (RCIF)				// is it the serial port receive interrupt ?
	{
		while(!TXIF) {		// wait for serial register to be sent, if there is still something in there
			nop();
		}
		rec = RCREG;		// Get the received character
		TXREG = rec;		// write to serial register -> start transmission

		RCIF = 0;			// reset serial port receive interrupt flag
	}
	int_restore_registers
}

void InitUSART()
{
	PORTA = 0;
	PORTB = 0;
	PORTC = 0;
	
	BRGH = 1;		// high speed serial port mode
	SPBRG=25;		// Set 9600 baud for 4 MHz oscillator
	SYNC = 0;		// Clear SYNC bit ; Set_Async_Mode;
	SPEN = 1;		// Set serial port enable
	TX9 = 0;			// 8-bit transmissions
	TXEN = 1;		// Enable transmission
	RCIE = 1;		// Rx interrupts are desired
	RX9 = 0;			// 8-bit receptions
	CREN = 1;		// Enable reception
}

void initint()
{
	GIE = 1; 		// Set Global Interrupt Enable
	PEIE = 1;		// Set Peripheral Interrupt Enable
}

void main(void)
{
	InitUSART();
	initint();
	while(1) {
		nop();
		nop();
	}
}