// SWR/Wattmeter Project Using C
// The programmer is a PICSTART Plus, and the microcontroller is a PIC16F72.
// This program was created and uploaded into the microcontroller with MPLAB v8.10 and HI-TECH C PRO v9.60PL3 (free version) for the PIC-10-12-16 MCU Family v9.60PL3.
// The OS is Windows XP.  HI-TECH C PRO v9.60PL3 does not work with Windows 98.

// The wattmeter display parameters:
//	LED			A/D range	VF2 range	Approx. Power	Power Output Range		LED color
//	D11			8-10		.32-.45V	.28W			.20-.40W				blue/green
//	D12			11-15		.45-.63V	.56W			.40-.79W				blue/green
//	D13			16-22		.63-.89V	1.1W			.79-1.6W				blue/green
//	D14			23-31		.89-1.3V	2.2W			1.6-3.2W				blue/green
//	D15			32-44		1.3-1.8V	4.5W			3.2-6.3W				blue/green
//	D16			45-63		1.8-2.5V	8.9W			6.3-13W					blue/green
//	D17			64-89		2.5-3.5V	18W				13-25W					blue/green
//	D18			90-127		3.5-5.0V	35W				25-50W					blue/green
//	D19			128-179		5.0-7.1V	71W				50-100W					yellow
//	D20			180-255		7.1-10V		>100W			100-200W				red

// The SWR meter display parameters:
//	LED		Reflection ratio range	Approx. SWR		SWR range		LED color
//	D1		0 to 1/9				1.1				1.00 to 1.25	blue/green
//	D2		1/9 to 2/9				1.4				1.25 to 1.57	blue/green
//	D3		2/9 to 1/3				1.8				1.57 to 2.0		blue/green
//	D4		1/3 to 4/9				2.3				2.0 to 2.6		yellow
//	D5		4/9 to 5/9				3				2.6 to 3.5		yellow
//	D6		5/9 to 2/3				4				3.5 to 5		yellow
//	D7		2/3 to 7/9				6				5 to 8			red
//	D8		7/9 to 8/9				11				8 to 17			red
//	D9		8/9 to 1				35				>17				red
//	D10		>1						infinity		infinity		red

// All of the LEDs in the SWR meter and wattmeter displays remain dark when transmitted power is under 200mW.

// Port A pin 4 is different from all of the other pins, because it is an open port pin.
// I couldn't find a way to control the corresponding LED D5 through the PORT value,
// so I am using the TRIS value to control the impedance.  Note also that this pin is
// connected to 5V instead of ground through the series resistor and LED.

// This program uses 3EBh/800h (1003/2048, 49.0%) words of program space.
// This program uses Bh/80h (11/128, 8.6%) bytes of data space.

// The files stdlib.h and pic.h need to be included in the list of header files shown in the workspace window.
// These files are in the C:\Program Files\HI-TECH Software\PICC\PRO\9.60\include directory.
#define __16F72
#include <stdlib.h>
#include <pic.h>

__CONFIG (XT&WDTDIS&PWRTDIS&BORDIS&UNPROTECT); // Set the configuration bits: 
// XT=crystal oscillator, WDTDIS=Watchdog Timer disabled, PWRTDIS=Power Up Timer disabled, BORDIS=Brown Out Detector disabled, UNPROTECT=code is unprotected
// Go to Configure->Configuration Bits to confirm configuration bits.
// The crystal is a 3.579545 MHz crystal resonator.

unsigned char fwd, refl, ninths, count, prod_1, prod_256;

void start(void)
	{
	RP1=0; RP0=1; // Select Register Bank 01.
	TRISA=0b00000011; // Set pins RA5, RA4, RA3, and RA2 as outputs and pins AN1 and AN0 as inputs.
	TRISB=0b00000000; // Set RB7-RB0 pins as outputs.
	TRISC=0b00000000; // Set RC7-RC0 pins as outputs.
	ADCON1=0b00000100; // RA0 and RA1 are analog.
	// Because RA3 is an output, the digital output will be converted to an analog value.
	RP0=0; // Select Register Bank 00.
	GIE=0; // Disable Global Interrupt
	}

void delay_10_usec (void)
	{
	count=0;
	while (count<143)
		{
		// One instruction takes up 1/4 of a clock cycle (69.8 nsec given a 3.57945 MHz crystal resonator).  143 instructions take 10 usec.
		count++;
		}
	}

void delay_1_msec (void)
	{
	count=0;
	while (count<100)
		{
		delay_10_usec(); // 100 delays of 10 usec each.
		count++;
	}

void get_fwd(void) // Get the analog input representing forward voltage and store the result in the function fwd.
	{
	RP1=0; RP0=1; // Select Register Bank 1.
	ADCON1=0b00000100; // V_REV=V_DD; RA0, RA1, and RA3 are analog; RA2 and RA5 are digital
	RP1=0; RP0=0; // Select Register Bank 0.
	ADCON0=0b10000001; // A/D conversion clock rate of FOSC/32, Channel 0 (RA0), A/D conversion not in progress, A/D converter module operating
	// Bits 5-3: select channel
	// Bit 2 (A/D conversion status bit, ADGO): 0=A/D conversion not in progress, 1=A/D conversion in progress
	// Bit 0 (A/D on bit, ADON): 0=A/D converter module not operating, 1=A/D converter module operating
	delay_10_usec; // Let the A/D converter module continue operating for 20 usec.
	ADGO=1; // Start the A/D conversion process
	while (ADGO==1) // Continue to keep the A/D converter active until the A/D conversion process completes.
		{}
	fwd=ADRES; // fwd=the result of the A/D conversion=V_F_2*255/10V
	RP1=0; RP0=1; // Select Register Bank 1
	ADCON1=0b00000111; // V_REF=V_DD; RA0, RA1, RA2, RA3, and RA5 are digital
	RP1=0; RP0=0; // Select Register Bank 0.
	// Place break point here and provide value for fwd in watch window.
	}

void clear_displays (void)
	{
	RA5=0; RC0=0; RC1=0; RC2=0; RC3=0; RB0=0; RC7=0; RC6=0; RC5=0; RC4=0; // Turn off LEDs D11-D20, respectively.
	RB7=0; RB6=0; RA2=0; RA3=0;  // Turn off LEDs D1-D4, respectively.
	RP1=0; RP0=1; // Select Register Bank 1.
	TRISA4=1; // Port A pin 4 is now an input pin.  This means high impedance, low current, and a dark LED D5.
	RP1=0; RP0=0; // Select Register Bank 0.
	RB5=0; RB4=0; RB3=0; RB2=0; RB1=0; // Turn off LEDs D6-D10, respectively.
	}

void displaywatt(void)
	{
	if (fwd>=180)
		{RC4=1;}
	else if (fwd>=128)
		{RC5=1;}
	else if (fwd>=90)
		{RC6=1;}
	else if (fwd>=64)
		{RC7=1;}
	else if (fwd>=45)
		{RB0=1;}
	else if (fwd>=32)
		{RC3=1;}
	else if (fwd>=23)
		{RC2=1;}
	else if (fwd>=16)
		{RC1=1;}
	else if (fwd>=11)
		{RC0=1;}
	else
		{RA5=1;}
	}

void get_refl(void)
	{
	RP1=0; RP0=1; // Select Register Bank 1.
	ADCON1=0b00000100; // RA0 and RA1 are analog.
	RP1=0; RP0=0; // Select Register Bank 0.
	ADCON0=0b10001001; // A/D conversion clock rate of FOSC/32, Channel 1 (RA1), A/D conversion not in progress, A/D converter module operating
	// Bits 5-3: select channel
	// Bit 2 (A/D conversion status bit, ADGO): 0=A/D conversion not in progress, 1=A/D conversion in progress
	// Bit 0 (A/D on bit, ADON): 0=A/D converter module not operating, 1=A/D converter module operating
	delay_10_usec; // Let the A/D converter module continue operating for 20 usec.
	ADGO=1; // Start the A/D conversion process
	while (ADGO==1) // Continue to keep the A/D converter active until the A/D conversion process completes.
		{}
	refl=ADRES; // refl=the result of the A/D conversion=V_R_2*255/10V
	RP1=0; RP0=1; // Select Register Bank 1
	ADCON1=0b00000111; // RA2, RA3, RA4, and RA5 are digital.
	RP1=0; RP0=0; // Select Register Bank 0.
	// Place break point here and provide value for refl in watch window.
	}

void get_refl_ratio(void)
	{
	// We already know that refl/fwd<1 at this point.
	// Now we only need to determine how many full units of 1/9 there are in this ratio.
	// refl/fwd=ninths/9, 9*refl=ninths*fwd, 9*refl-ninths*fwd=0
	// ninths is maximum unsigned char for which 9*refl-ninths*fwd>=0
	// prod=256*prod_256+prod_1 stores the result of the addition and subtraction operations in the process.
	prod_1=0; prod_256=0; count=0; ninths=0;
	while (count<9)
		{
		// Increment prod by refl.  If prod_l+refl>255, then increment prod_256 by 1.
		if (prod_1>255-refl)
			{prod_256++;}
		prod_1=prod_1+refl;
		count++;
		}
	// Now prod=9*refl.  Time to keep subtracting fwd from prod until prod<fwd (prod-fwd<0).
	while (prod_256>0 | prod_1>=fwd)  // This means prod>=fwd.  The while loop is repeated until prod<fwd.
		{
		// Decrement prod by fwd.  If prod_1<fwd, then decrement prod_256.
		if (prod_1<fwd)
			{prod_256--;}
		prod_1=prod_1-fwd;
		ninths++;
		}
	}

void displayswr(void)
	{
	if (ninths==8)
		{RB2=1;} // Light LED9.
	else if (ninths==7)
		{RB3=1;} // Light LED8.
	else if (ninths==6)
		{RB4=1;} // Light LED7.
	else if (ninths==5)
		{RB5=1;} // Light LED6.
	else if (ninths==4)
		{
		RA4=0; // This is a prerequisite for lighting LED D5.
		RP1=0; RP0=1; // Select Register Bank 1.
		TRISA4=0; // Port A pin 4 is now an output pin.  This means low impedance, high current, and a lit LED D5.
		RP1=0; RP0=0; // Select Register Bank 0.
		} // Light LED5.
	else if (ninths==3)
		{RA3=1;} // Light LED4.
	else if (ninths==2)
		{RA2=1;} // Light LED3.
	else if (ninths==1)
		{RB6=1;} // Light LED2.
	else if (ninths==0)
		{RB7=1;} // Light LED1.
	}

void main()
	{
	start(); //Set the initial configurations.
	while (1) 
		{
		get_fwd();
		clear_displays();
		if (fwd>=8) // All LEDs remain dark unless transmitted power is >=200mW
			{	
			displaywatt();
			get_refl();
			if (refl>=fwd) // refl/fwd>=1, SWR is infinite
				{
				RB1=1; // Light LED D10
				}
			else  // refl/fwd<1, SWR is finite
				{ 
				get_refl_ratio(); // We now have a value for ninths.  This value (0-8) determines which SWR meter LED lights up.
				displayswr();  // This only applies for LEDs D1-D9.  The case involving LED D10 is already covered.
				}

			}
		
		delay_1_msec;
		}
	}