Serial communication between two PICs

[muhilazhagan]

I couldn't establish serial communication between two pic microcontrolllers.

This is my code for transmitter.

[Mike Walne]

Tell us what you can see.

Mike

[PCM programmer]

[Mike Walne]

Divide and conquer helps in this situation.

Test the TX by getting it to talk to a PC.
Test the RX by getting a PC to talk to it.
(You may need a temporary MAX232 chip, or the like.)
THEN get TX and RX to talk to each other.

Mike

[muhilazhagan]

thanks guys i modified the program still i couldnt get any output

#include <16f877a.h>
#fuses HS,NOLVP,NOWDT
#use delay(clock=20000000)
#use rs232(baud=9600,parity=N,xmit=PIN_C6,rcv=PIN_C7,bits=8,errors)
//transmitter
void main()
{

delay_ms(100);
putc('c');
while(true);
}

receiver:

void main()
{
int c;
lcd_init();
delay_ms(50);
c = getc();
printf(lcd_putc," %02c",c); // this line is not executing
while (1);
}[/code]

even now i could see nothing in my lcd

[muhilazhagan]

thanks guys i modified the program still i couldnt get any output

[Ttelmah]

Start with learning to properly use the code buttons.....

Then look through the forum. Simple thing. LCD's need _time_ to wake before they can be used. The original Hitachi displays needed 90mSec (in their data sheet), but this is from when they 'start to wake', which is a lot higher voltage than the PIC needs. This is why the driver has a short delay in it, _but_ most of the 'clone' displays need longer. Something like 0.5 seconds typically.

master:

[Mike Walne]

Are your PICs running at all?
Can you do the simple LED flasher?
(At the correct speed!)
Is your TX actually transmitting?
Will the LCD do a "Hello World" test?
...........
...........

It's all basic debugging.

Mike

[muhilazhagan]

all those things are done and my pic interfaced with rtc is displaying time in lcd so no problem with pic.

[Mike Walne]

How do you KNOW your TX is transmitting at the correct rate?

Mike

PS Have you tried my previous divide and conquer suggestion?

[Ttelmah]

and, how is the connection made between the PIC's?.

[ezflyr]

[muhilazhagan]

finally done thankyou so much for ur time.
i had the problem with my hardware

thanks once again

[muralid]

guys i am new to this forum.
I want transfer the message from one pic to another pic. I mean not a single character but a string.

[Ttelmah]

Understand one thing. In C, there is actually no such thing as a string!.....

I'm being pedantic, but other languages have a 'string' as a type. In C, a 'string' is just an array of characters _terminated with a '\0' (NULL)_.

Now if you look in the library 'input.c', you will find the source code for a function 'get_string', which receives characters, and adds them to an array, until it sees a carriage return, or too many characters arrive.
Sending or receiving a 'string' is just a matter of repeatedly handling single characters. It's up to use to decide what to use to signal the 'end' in transmission (typically line feed or carriage return is commonly used).

printf("A line of text\r");

Sends the sequence of characters 'A line of text' and the carriage return to the serial.

//With this as a defined variable
char buffer[20];

get_string(buffer,20);

Will fetch a maximum of _19_ characters from the serial, returning when the carriage return is seen.

'Why 19'?.

Remember my comment about a C string having a terminating NULL. This means a 19 character string needs 20 characters of storage. The get_string function takes it's 'max' value as the maximum it is allowed to put into the array, so will get 19+terminator, if told to limit to 20 characters. Look at the code, right near the start you will see the line 'max-=2', which it to allow first for the arrays being zero referenced (-1), and then for the terminator (-1).

So after this call on a receiving device connected to the machine sending using the printf, the array 'buffer' will contain "A line of text\0". Note not the carriage return, but a terminator instead.