One wire in PIC16F84A

[briantk_1988]

Hi everyone,

I'm just a new "apprentice" in this field. I'm contemporarily learning how to transfer data from one PIC16F84A to the other one, including how to receive the data, of course. I can read and understand MPAsm, Mikro Basic and CCS C quite well; so, if you know about this, you can help me in the aforementioned language. Thank you in advance.

B

[namqn]

Hi everyone,

I'm just a new "apprentice" in this field. I'm contemporarily learning how to transfer data from one PIC16F84A to the other one, including how to receive the data, of course. I can read and understand MPAsm, Mikro Basic and CCS C quite well; so, if you know about this, you can help me in the aforementioned language. Thank you in advance.

B

Hi briantk,

There are many ways to do what you want, using different interface protocols and standards. Unfortunately, PIC16F84A doesn't give you much power to do a lot of stuff in implementing those protocols and standards.

So, could you be more specific on what you are trying to do?
What sort of data are you transferring?
How fast would you like your data to be transferred?
Have you got any idea about the interface protocol/standard?

Cheers,

[briantk_1988]

Thanks a lot for replying me.

I'm trying to make a simple calculator. As far as I am concerned, an LCD display requires 6 pins from the microcontroler, a simplest keypad needs 8 more pins --> we need at least 14 IO pins which is impossible for an PIC16F84A. Unfortunately, since I haven't a clue about microcontroler before, I just though everything was the same which made me I got the PIC16F84A. Now, I'm thinking that I might use one PIC6F84A for the keypad and then use one wire interface to transmiss the information to the other one which will manipulate the data and then display in the LCD. I did read the onewire example in MikroBasic but it's not satifiable, for the example is just for getting data from a themometer (DS1820). Furthermore, I think that I don't need a very high speed to do this task. Also, I'm just a novice, I have a very humble idea about interface protocol/standard. So, if anyone have any idea about what i gotta do, I'm very grateful to know.

Thanks in advance

[BêBop]

Chảo Briantk,
I agree with namqn, that the 'f84 is not the best choice. It is old, and has no USART, etc. etc. Next time try a 16F628A, or a 16F88. You can free up some pins by using a 2 wire LCD interface, though. Take a look at this site for the hardware:

http://www.rentron.com/Myke1.htm

He gives examples in assembly, and somewhere I have source in ccs C to run it. I will try and find my source if you wish to go this route. I'm quite busy these days as I will move back to Canada in 3 weeks, but I'll watch this forum to see if you are interested.

Regards

[briantk_1988]

Thanks so much. It must be the best that you can provide me with the source in CCS C. I hope you can post it soon

Regards

Br

[BêBop]

Chảo,
I hope this works, but if you have any questions, I'll keep watching here...
first the driver

////////////////////////////////////////////////////////////////////////////
//// Library for a 2 wire LCD interface using an 74hc174		////
////									////
////									////
////////////////////////////////////////////////////////////////////////////

#ifndef LCD_clk
#define LCD_data 	PIN_B2
#define LCD_clk		PIN_B1
#endif

void LCDInit(void)	{		//  Initialize the LCD I/O Pins

	Dlay = RTC +20;
	while (Dlay != RTC);

	LCDNybble(0x003, 0);  // send init command
	Dlay = RTC + 6;			// wait > 5 mSec for
	while (Dlay != RTC);	// LCD to accept cmd

	LCDNybble(0x003, 0);  // send init command
	Dlay = RTC + 1;			// wait > 160 uSec for
	while (Dlay != RTC);	// LCD to accept cmd

	LCDNybble(0x003, 0);  // send init command
	Dlay = RTC + 1;			// wait > 160 uSec for
	while (Dlay != RTC);	// LCD to accept cmd

	LCDNybble(0x002, 0);  // send init command	0000 0010
	Dlay = RTC + 6;			// wait > 5 msec for
	while (Dlay != RTC);	// LCD to accept cmd

	LCDByte(0x028, 0);		// step 6, set operating	0010 1000

	LCDByte(0x008, 0);		// step 7, display off		0000 1000

	LCDByte(0x001, 0);		// step 8, clear display	0000 0001

	LCDByte(0x006, 0);		// step 9, shift		0000 0110

	LCDByte(0x00E, 0);		// step 10, display on		0000 1110

}  //  End LCDInit

void LCDNybble(char Nybble, char RS) { 		//  Send Nybble to LCD

	int i; // removed unsigned from before int

	output_low(PIN_B2);	//Data = 0; // Clear the '174 
	for (i = 0; i < 6; i++) { 		// Repeat for six bits 
		//Clock = 1; Clock = 0; 	// Write the "0"s into the '174 
		output_high(PIN_B1);
		output_low(PIN_B1);
		}   //  endfor 

	//Data = 1; 				// Output the "AND" Value 
	output_high(PIN_B2);
	//Clock = 1; Clock = 0;
	output_high(PIN_B1);
	output_low(PIN_B1);
//	Data = RS; 				// Output the RS Bit Value 
	if (RS>0)output_high(PIN_B2);
		else output_low(PIN_B2);
	//Clock = 1; Clock = 0; 
		output_high(PIN_B1);
		output_low(PIN_B1);

	for (i = 0; i < 4; i++) { 		// Output the Nybble 
		if ((Nybble & 0x008) != 0) 
		//	Data = 1; 		// Output the High Order Bit
			output_high(PIN_B2);
		else 
			//Data = 0; 
			output_low(PIN_B2);
		//Clock = 1; Clock = 0; 		// Strobe the Clock 
		output_high(PIN_B1);
		output_low(PIN_B1);

		Nybble = Nybble << 1; 		// Shift up Nybble for Next Byte 
		}  //  endfor

//	Data = 1; Data = 0; 			// Toggle the "E" Clock Bit 
	output_high(PIN_B2);
	output_low(PIN_B2);
}  //  End LCDNybble 

void LCDByte(char myByte, char RS) {	 //  Send Byte to LCD	
	int LBDlay;

	LCDNybble((myByte >> 4) & 0x00F, RS);	//  Send High Nybble

	LCDNybble(myByte & 0x00F, RS);		//  Send Low Nybble

	if ((myByte < 4) && (RS == 0))  // type of instruction
		LBDlay = RTC + 6;
	else
		LBDlay = RTC + 2;

	while (LBDlay != RTC); // command to complete wait
}  //  End LCDByte

void send_c(char myByte) {	 		//  Send Byte to LCD	
	int LBDlay;
	char RS = 1;

	LCDNybble((myByte >> 4) & 0x00F, RS);	//  Send High Nybble

	LCDNybble(myByte & 0x00F, RS);		//  Send Low Nybble

	if ((myByte < 4) && (RS == 0))  	// type of instruction
		LBDlay = RTC + 6;
	else
		LBDlay = RTC + 2;

	while (LBDlay != RTC); 			// command to complete wait
}  //  End send_c

void SecondLine(void) {
	LCDByte(0xC0, 0);
	} // end SecondLine

void Home(void) {
	LCDByte(0x02, 0);
	} // end Home

void ClearLCD(void) {
	LCDByte(0x01, 0);
	} // end ClearLCD

then a test program

#if defined(__PCM__)
#include <16F84A.h>
#fuses HS,NOWDT,NOPROTECT
#use delay(clock=4000000)
#use rs232(baud=9600, xmit=PIN_B6, rcv=PIN_B7)
#endif

#include "LCDHG.C"
#include <STDIO.h>
#include <string.h>

#define CDCLK Pin_B1

//#define LCDDAT Pin_B2

void main() {
	int x, y, c;
	x = 0x01;
	y = 0x01;
	c = 0x55;
//	char *c;// = "H";
//	char string[20];
	//c="H";

	lcd_init();
	lcd_gotoxy(x, y);

	lcd_putc("\f");
	lcd_putc(0x55);

	while(1) {
	;
	} // end while
}