#include <stdio.h>
#include <stdlib.h>

#include "c8051f350.h"

// Peripheral specific initialization functions,
// Called from the Init_Device() function
void PCA_Init()
{
    PCA0MD    &= ~0x40;	// disable watchdog timer
    PCA0MD    = 0x00;
}

void Timer_Init()
{
	TCON      = 0x40;	// configure timers for 9600 bit/s UART data rate
	TMOD      = 0x20;
	CKCON     = 0x01;
	TH1       = 0x60;
}

void UART_Init()
{
	SCON0     = 0x10;	// enable UART for 8-bit, variable baud mode
}

// Configure the ADC:
// 100Hz sample rate, unipolar mode
// gain=1, external voltage reference
// analog input buffers are bypassed
// ADC input is AIN7 and GND
void ADC_Init()
{
	ADC0CN    = 0x00;	// disable ADC, will be enabled later
	ADC0CF    = 0x04; 
	ADC0MD    = 0x80;
	ADC0CLK   = 0x04;
	ADC0DECH  = 0x00;
	ADC0DECL  = 0xBE;
	ADC0MUX   = 0x78;
}

void Port_IO_Init()
{
	P1MDIN    = 0xBF;	// P1. is analog
	P0MDOUT   = 0x90;	// P0.4 (UART TX) and P0.7 (LED) are push-pull, digital
	P1SKIP    = 0x40;
	XBR0      = 0x01;
	XBR1      = 0x40;
}

void Oscillator_Init()
{
	OSCICN    = 0x82;	// internal oscillator, 12.25MHz
}

// Initialization function for device,
void Init_Device(void)
{
	PCA_Init();
	Timer_Init();
	UART_Init();
	ADC_Init();
	Port_IO_Init();
	Oscillator_Init();
}

unsigned char SIn(void)
{
	while (!RI);	// wait for a byte
	RI=0;
	return SBUF;	// return the byte
}

void SOut(char a)
{
	TI=0;
    SBUF=a;			// transmit a byte
	while (!TI);	// wait for end of transmission
}

void CalibrateADC(void)
{
	ADC0MD = 0x81;			// ADC0 MODE: FULL INTERNAL CALIBRATION 
	while(AD0CBSY); 		// end of cal step 
	while(ADC0MD & 0x07); 	// wait return to IDLE!!! 
	AD0INT=0;
}

// Do continuos sampling
// every sample will be sent to the host
// detect also heart beats and flash the LED accordingly
void HeartBeats(void)
{
	unsigned char c;
	int x2,x1,y;
	
	CalibrateADC();				// ADC calibration is required before measurements
	x1=0;						// initial value of data
	y=0;						// initial value of filtered data
	c=0;						// initialize UART input variable
	ADC0MD = 0x83;				// enable ADC
	do
	{
		while(!AD0INT); 		// wait for end of conversion 
		AD0INT=0;				// clear flag
		SOut(ADC0H);			// send ADC most significant byte
		SOut(ADC0M);			// send ADC middle byte
		SOut(ADC0L);			// send ADC least significant byte
		x2=(ADC0H<<8) |	ADC0M;	// most significant 16-bits of data
		y=((243L*y) >> 8)+x2-x1;	// (243L*y)/256+x2-x1 : do digital high-pass filtering
		P0_7=(y>0);				// drive LED to visualize heart beats
		x1=x2;					// shift data for digital high-pass filtering
		if (RI) c=SIn();
	} while (P1_0 && c!=27);	// stop if button is not pressed or ESC received
	ADC0MD = 0x80;
}

void main(void)
{
	unsigned char i;

	Init_Device();

	while (1)
	{
		i=SIn();		// wait for a byte
		SOut(i);		// return to the host for "software handshaking"
		if (i=='m')		// if 'm' is received, start measurement
		{
			HeartBeats();
		}
	}
}