PIC - PIC Comm

[dgcarter]

I've been working on a little robot project in PIC Pro Basic.

I'm trying to establish some sort of communication between two PIC Microprocessors. 1 being a PIC16F84A with a keypad, the other a PIC16F877A controling the robot.

The PIC16F84A scans the kaypad and stores the key pressed into a variable. The PIC16F877A needs to recieve this value and store it in its own variable.

I've experimented with RS232 (SERIN, SEROUT) but I jus can't seem to get it working. There is 1 meter of cable between the two pics so could that be the reason?

Any suggestions as to what I can do to achieve communication between these two pics?

[mister_e]

Try one thing first.

Connect your PIC16F84 to your PC and send some data to any terminal softare (hyperterminal, TeraTerm, RealTerm, Microcode Serial communicator) and see if you receive any data.

do the same but From your PC to your 16F877,

once both work, try your PIC to PIC communication on small distance, then move on with long cable run. You may want to use RS232 driver for longer run.

[Archangel]

OUT) but I jus can't seem to get it working. There is 1 meter of cable between the two pics so could that be the reason?

Any suggestions as to what I can do to achieve communication between these two pics?

Hello dgcarter, and welcome.
Since this is your first post, we know nothing about you, so I must ask, is this your first project, or do you have some experience? Have you tried the basic blinking LED yet? 1 meter should work easily, so if you would post your code using the code tags as shown in Mister_e's signature, (shown in green) let's get started.

[dgcarter]

Hello again...

I've been using PBP for a while now, I've blinked many many LED's, Swiched lights on and off with my PC and a PIC via RS232, and now I have a robot which follows a black line.

Essentially I have a PIC 16F84A on a 4x3 keypad, I've tried getting it to communicate via RS232 with my Robot (PIC16F877).

Heres the Keypads code...

INCLUDE "modedefs.bas"          
             
' Declare Variables...
Col1      VAR PORTA.0
Col2      VAR PORTA.1
Col3      VAR PORTA.2

Row1      VAR PORTB.4
Row2      VAR PORTB.5
Row3      VAR PORTB.6
Row4      VAR PORTB.7

LED       var PORTB.1
SERTX     var PORTB.2
SERoK     var PORTB.3

Key       var word

' Setup Ports

input row1 : input row2 : input row3 : input row4
output col1 : output col2 : output col3 : output SERTX

' Setup Var

key  = 20

' Program Start
Boot:
    high led
    pause 500
    low led
    pause 100
    high led
    pause 100
    low led
    pause 2000
    high serok
    goto main

Main:
    gosub ScanKeys
    if key != 20 then gosub transmit
    goto main

ScanKeys:    
    high col1
    pause 50
        if row1 = 1 then Key = 1
        if row2 = 1 then Key = 4
        if row3 = 1 then Key = 7
        if row4 = 1 then Key = 10                    
    low col1
            
    high col2
    pause 50
        if row1 = 1 then Key = 2
        if row2 = 1 then Key = 5
        if row3 = 1 then Key = 8
        if row4 = 1 then Key = 0     
    low col2
        
    high col3
    pause 50
        if row1 = 1 then Key = 3
        if row2 = 1 then Key = 6
        if row3 = 1 then Key = 9
        if row4 = 1 then Key = 11     
    low col3
                
    return
    
Transmit:
    gosub flash 
    serout sertx,4,[55,key]
    pause 50
    key = 20
    low led
    return
    
Flash:
    high led
    pause 50
    low led
    pause 50
    high led
    pause 50
    return
    
end

Ok, so the PIC16F84A raises SERoK to logic 1 which tells the PIC16F877A to accept serial communication.

PIC16F877A Code:

INCLUDE "modedefs.bas"

' Define LCD registers and bits
Define    LCD_DREG     PORTA
Define    LCD_DBIT     0
Define    LCD_RSREG    PORTA
Define    LCD_RSBIT    4
Define    LCD_EREG     PORTA
Define    LCD_EBIT     5
DEFINE    LCD_LINES    4

'Define Aliases
RHF       var          PORTB.0
RHB       VAR          PORTB.1
LHF       VAR          PORTB.2
LHB       VAR          PORTB.3
LineCom   var          PORTB.4
LEDS      var          PORTB.5
SERoK     var          PORTB.7
SERRX     var          PORTB.6

'Define Vars
Dat       var          byte

ADCON1 = 7

'Begin program
Boot:
    dat = 20
    Pause 500       ' Wait for LCD to startup
    gosub display
    low leds
    repeat
        Lcdout $FE, $C0, "!! Insert Ctrl !!"
        Lcdout $FE, $94, "Waiting..."
        pause 100
    until serok = 1
    goto modeselect       
    
ModeSelect:
    Lcdout $FE, $C0, "!! Select Mode !!"
    Lcdout $FE, $94, "Waiting..."
    serin SERRX,4,[55],Dat
    pause 50
Discon:
    Lcdout $FE, $94, "Pls Discon..."
    if serok = 0 then GoMode
    goto discon

GoMode:
    if dat <> 20 then
    select case dat
        case 20
            goto boot
        case 2
            goto linefollow
    end select
    endif
goto boot
      
Display:   
   Lcdout $fe, 1   ' Clear LCD screen
   Lcdout "PIC-Bot... v1.0"
   Lcdout $FE, $94, "Pls Wait..."
   Pause  1000
   return
   
'Check for controler
ChkCtrl:
if serok = 1 then modeselect
return
        
'Line Follow loop    
LineFollow:
    Lcdout $FE, $C0, "~~ LiNe FoLlOw ~~"
    Lcdout $FE, $94, "...Scan Line..."
    low RHF
    low LHF
    PWM LHF,60,18
    pause 100
    if linecom = 0 then gosub moveleft
    low RHF
    low LHF
    PWM RHF,60,18
    pause 100
    if linecom = 0 then gosub moveright
    gosub chkctrl
    goto linefollow
    
MoveLeft:
    Lcdout $FE, $94, "Correct Left"
    repeat
        low RHF
        low LHF
        PWM RHF,60,20
        PWM LHb,60,20
        pause 100
    until linecom = 1
    pause 50
    low RHF
    low LHF
    PWM RHF,60,18
    return
    
MoveRight:
    Lcdout $FE, $94, "Correct Right"
    repeat
        low RHF
        low LHF
        PWM LHF,60,20
        PWM rHb,60,20
        pause 100
    until linecom = 1
    pause 50
    low RHF
    low LHF
    PWM LHF,60,18
    return
    
end

Now the Robot waits until the keypad unit is pluged in, then it waits until the digit 2 is sent serially (by pressing 2 on the keypad), then it askes you to dicconnect the keypad unit (SERoK changes from logic 1 to logic 0) and it executes the program IF 2 was pressed.

[mister_e]

When a PIC have a built-in USART use it.. PIC16F877A have it, switch to HSERIN

SEROUT on one side
HSERIN on the other side

Begin with it, then add some sugar around...

[dgcarter]

When a PIC have a built-in USART use it.. PIC16F877A have it, switch to HSERIN

SEROUT on one side
HSERIN on the other side

Begin with it, then add some sugar around...

I assume then I use PIN 26, labled RX on the PIC?

[mister_e]

yes indeed, and you may need to add some DEFINEs at the top of your code as well.

Well, by default @4MHz it's already set @2400 baud, so... humm... you may not need any Define at all... it's just good programming