// PIC I2C SLAVE COMPONENT
//  counter & adc & port-I/O
// 
// ver 1.0 2025-10-4 for PIC16F1938   
//
#include "16F1938.H"
#fuses INTRC_IO,NOWDT,NOMCLR,NOBROWNOUT,NOLVP,PUT
#device ADC=10
#use I2C(slave,fast,sda=PIN_C4,scl=PIN_C3,address=0xa0,force_hw)

#use delay(internal=32MHz)
#use fast_io(A)
#use fast_io(B)
#use fast_io(C)

unsigned int16 old_time;
unsigned int16 upper_time;
unsigned int16 lower_time;
unsigned int16 trans_word16;
int	 count_flag = 1;	

int16 get_ad()
{
	int1	done;
	int16	value;
	read_adc(ADC_START_ONLY);
	done = adc_done();
	while(!done) done=adc_done();
	value=read_adc(ADC_READ_ONLY);
	return(value);
}

#INT_SSP
void ssp_interupt (){
	int code,adrs,state;

	state=i2c_isr_state();
	if(state>=0x80)  		//addrs match with master read
	{
		if(state==0x80) i2c_write((trans_word16 >> 8)&0xff);
        else		    i2c_write(trans_word16 & 0xff);
	}
    else if(state >0){		//adrs match with master write
        code=i2c_read(1);
		switch(code){
		case	0x00:		// counter reset & count run
			set_timer1(1);
			count_flag = 1;
			old_time   = 0;
			upper_time = 0;
			lower_time = 0;
			break;
		case	0x01:		// stop counter
			if(count_flag){
				lower_time=(unsigned int16)get_timer1();
				if(old_time > lower_time) upper_time++;
			}
			count_flag = 0;
			break;
		case	0x02:		// upper time set
			trans_word16 = upper_time;	break;
		case	0x03:		// lower time set
			trans_word16 = lower_time;	break;
		case	0x10:	// ADC CH0
		case	0x11:	// ADC CH1
		case	0x12:	// ADC CH2
		case	0x13:	// ADC CH3
			set_adc_channel(code-0x10);
			trans_word16 = get_ad();
			trans_word16 = trans_word16 << 2;
			break;
		case	0x20:trans_word16 = input_b(); break;
		case	0x30:output_low(PIN_B0);		break;
		case	0x31:output_high(PIN_B0);		break;
		case	0x32:output_low(PIN_B1);		break;
		case	0x33:output_high(PIN_B1);		break;
		default:break;
		}
	}
	else adrs = i2c_read(1);
}

void io_select()
{
	set_tris_a(0xff);
	set_tris_b(0xff);
	set_tris_c(0xff);
	setup_timer_1(T1_EXTERNAL);
	set_timer1(0);
	setup_adc(ADC_CLOCK_INTERNAL);
	setup_adc_ports(sAN0 | sAN1 | sAN2 | sAN3);
	set_adc_channel(0);
	port_b_pullups(0xfc);
	output_drive(PIN_B0);output_high(PIN_B0);
	output_drive(PIN_B1);output_high(PIN_B1);
    output_float(PIN_C4);  	//I2C SDA pin float
    output_float(PIN_C3);  	//I2C SCL pin float
}

void main()
{
	unsigned int16 f;

	setup_oscillator(OSC_8MHZ | OSC_PLL_ON);
	io_select();
	count_flag = 1;	// count available
	old_time = upper_time = lower_time = 0;
	set_timer1(0);
    enable_interrupts(INT_SSP);
    enable_interrupts(GLOBAL);
	while(1){
		if(count_flag){
			f = get_timer1();
			if(old_time>f) upper_time++;
			old_time = lower_time = f;
			delay_ms(1);
		}
	}
}