Serin Serout Help

[MangoKid]

Currently I am working on a project that involes serial communication between one PIC and another. The task is to flash an led at a rate (77) sent via serial. the code is as follows.

Sender: PIC 16F877A

CLEAR
DEFINE OCS 4
TRISA = %000000000


LOOP1:
SEROUT PORTA.0, 3, [77]
GOTO LOOP1:
END

Receiver: PIC 12F683

CLEAR
ANSEL = 0
CMCON0 = 7
X VAR BYTE
HIGH GPIO.2
INPUT GPIO.1

LOOP1:
SERIN GPIO.1, 3, X
GPIO.3 = 1
PAUSE x
GPIO.3 = 0
GOTO LOOP1
END

any help would be appreciated thanks a lot

[cncmachineguy]

my guess is the LED is always on or you just see a blip once. try moving the serin outside of the loop. The way you have it it will be waiting for a serin every time through the loop. next problem is you are turning the led on, waiting "x" time, then turning it off. THEN you go right back to the top of the loop and turn it right back on.so if it doesn't hang on the serin, it turns on almost instantly. try adding a pause after you trun it off also. That is assuming GPIO.3 is your LED.

[Darrel Taylor]

On a 12F683, GPIO.3 is "Input Only" when not used as MCLR.
You'll need to use a different pin for the LED.

And the receiver has no way to know where each byte of serial data starts.
The sender is continually sending data and the receiver looks for data whenever it looks for it.

If the receiver starts looking in the middle of a byte, it doesn't know it's not the beginning of the transmission and will receive an invalid value.

There needs to be some sort of handshaking, so the sender knows when the receiver will be ready to receive something before sending it.
That will take another line between the two chips.
Or, tri-state signaling on the single line (no sample code available).

My recommendation ... add another line between the two chips, use SEROUT2/IN2 with FlowPin control.
You can use GPIO.3 for the serial input (put FlowPin on another pin).

[mackrackit]

Do not forget
INCLUDE "modedefs.bas"

And if you do not have enough pins for the flow control.
From the manual. We sometimes refer to this as "waiting" for a character to know where we are.

The list of data items to be received may be preceded by one or more qualifiers enclosed within brackets. SERIN must receive these bytes in exact order before receiving the data items. If any byte received does not match the next byte in the qualifier sequence, the qualification process starts over (i.e. the next received byte is compared to the first item in the qualifier list). A Qualifier can be a constant, variable or a string constant. Each character of a string is treated as an individual qualifier.

[MangoKid]

thanks for the post unfortunately i have made little progress. I have set the flowpin using Serin2 and serout2 and i am using proper pins. my baud rate may have some issues I'm trying to use the slowest one for now. Currently the circuit does nothing, no flashing or anything, but i have verified with an oscilloscope that data is being sent. Hear is the new code.

send:
CLEAR
DEFINE OCS
TRISA = %000000000

LOOP1:
SEROUT2 PORTA.0\PORTA.1, 3313, [DEC 77]
GOTO LOOP1:
END

recive:
CLEAR
ANSEL = 0
CMCON0 = 7
X VAR BYTE

LOOP1:
SERIN2 GPIO.1\GPIO.3, 3313, [DEC X]
pause x
GPIO.0 = 1
PAUSE x
GPIO.0 = 0
PAUSE X
GOTO LOOP1
END

thanks again any help would be appreciated.

[MangoKid]

Should I be using pull up resistors (22k, 4.7K, 2.2k)?

[mackrackit]

You will need to turn the analog off.
The two links below should help. For now, after you read the one from Melanie, use the one from Darrel.
http://www.picbasic.co.uk/forum/showthread.php?t=561
http://www.picbasic.co.uk/forum/cont...54-All-Digital

And if you could post all of your code and how the configs are set might also be helpful.