Serial Communication Problem

[elec_mech]

Joe and Luciano,

I appreciate the info up to this point, I do feel I've gotten a better grasp of what I'm trying to do and how the PIC works, yet I am as confused as ever.

Here's the latest code (not including the tons of modifications I've tried) that appears to do nothing. Joe, I also used the code you presented in the
"Can an asm interrupt contain gosub to a picbasic routine?" forum question which looked related to this subject.

Code:

include "modedefs.bas"

Trisb = %00000000
Trisc = %01000000
Portb = %00000000
Portc = %00000000
PIE1 = %00100001 'Allow Timer1 & serial in to cause a periheral interrupt.
INTCON = %11110000 ' Enable interrupt for Timer0 AND peripherals

RX var byte[40]
TX var byte[40]
i var byte

RCIF VAR PIR1.5
' Alias RCIF (USART Receive Interrupt Flag)



Main:


if RCIF = 1 Then
serin portc.7, T2400, PDA

'I've also tried: "RCREG = PDA" in place of "serin portc.7, T2400, PDA" to
'no avail

else
goto main
endif

goto DataOut


DataOut:

serout portc.6, T2400, [10, 13]

goto Main

I'm still using the Hyper terminal to check this out.


I have looked at the App Notes, the datasheet and the forums and I still cannot get my head around this. I believe I am running into a wall looking at the App Notes and datasheets because they explain EXACTLY how the PIC works with serial comms all the while using assembly, while PicBasic Pro takes care of many of these things yet not all. Do I need to set up interrupts, define registers and the like? Again, I appreciate the help, the info thus far has been great, I'm just not applying it right and I can't figure out why.

[elec_mech]

Whoops, I forgot to include this line immediately under DataOut:

serout portc.6, T2400, [PDA]

Sorry.

[mister_e]

Here's something to play with.

    '   Program to echo incoming serial data 
    '   Baudrate : 2400 Bauds
    '   Method :   Polling USART interrupts flags

    '   Pic Definition
    '   ==============
        ' Using PIC 18F2320 @ 4MHZ and bootloader
        '
        DEFINE LOADER_USED 1
        DEFINE OSC 4
        
    '   Hardware configuration
    '   ======================
        '
        '
        TRISC  = %10000000    ' PORTC.7 is the RX input
                              ' PORTC.6 is the TX output
    
    '   Serial communication definition
    '   ===============================
        ' Using internal USART and MAX232 to interface to PC
        '
        RCSTA = $90 ' enable serial port, 
                    ' enable continuous receive
                    '
        TXSTA = $24 ' enable transmit, 
                    ' BRGH=1
                    '
        SPBRG = 103 ' set baudrate to 2400                   
        
    '   Alias definition
    '   ================
        '
        '
        RCIF VAR PIR1.5     ' Receive  interrupt flag (1=full , 0=empty)
        TXIF VAR PIR1.4     ' Transmit interrupt flag (1=empty, 0=full)
        OERR var RCSTA.1    ' Overrun error
        CREN var RCSTA.4    ' Continuous receive
                
    '   Hardware initialisation
    '   =======================
        '
        '
        pause 10 ' safe start-up delay
    
Main:
    if oerr then  ' Overrun error?
       cren=0     ' clear it
       cren=1
       endif

    if RCIF then    ' incomming data?
       TXREG=RCREG  ' take it, send it
       while TXIF=0 ' wait untill transmit buffer is empty
       wend
       endif
    goto main

the following use HSERIN/HSEROUT statement. Since your PIC have internal USART... why not using it

    '   Program to echo incoming serial data 
    '   Baudrate : 2400 Bauds
    '   Method :   Polling USART interrupts flags

    '   Pic Definition
    '   ==============
        ' Using PIC 18F2320 @ 4MHZ and bootloader
        '
        DEFINE LOADER_USED 1
        DEFINE OSC 4
        
    '   Hardware configuration
    '   ======================
        '
        '
        TRISC  = %10000000    ' PORTC.7 is the RX input
                              ' PORTC.6 is the TX output
    
    '   Serial communication definition
    '   ===============================
        ' Using internal USART and MAX232 to interface to PC
        '
        DEFINE HSER_RCSTA 90h ' enable serial port, 
                              ' enable continuous receive
                              '
        define HSER_TXSTA 24h ' enable transmit, 
                              ' BRGH=1
                              '
        define HSER_SPBRG 103 ' set baudrate to 2400                   
        DEFINE HSER_CLOERR  1 ' automatic clear overrun error  
        
    '   Alias definition
    '   ================
        '
        '
        RCIF VAR PIR1.5     ' Receive  interrupt flag (1=full , 0=empty)
        TXIF VAR PIR1.4     ' Transmit interrupt flag (1=empty, 0=full)
        
    '   Variable definition
    '   ===================
        '
        '
        SerialData var byte
        
    '   Hardware initialisation
    '   =======================
        '
        '
        pause 10 ' safe start-up delay
    
Main:
    if RCIF then            ' incomming data?
       hserin  [Serialdata] ' take it
       hserout [serialdata] ' send it
       endif
    goto main

hope this help

[elec_mech]

Mister_E,

Thank you for the lovely code! It works nicely and I've been examining it while referencing the datasheet and I have learned a good deal. I then tried to manipulate it to work with my application and I've hit a wall. Initially I'm trying to look at a string of characters sent via the hyperterminal, particularly the first and last bit.

Now, perhaps I'm going into overkill with caution, but I only want to store the string into a variable array if the string starts with a ASCII "!". I then want to continue taking the rest of the string until an ASCII "L" is seen.

The idea being if for some reason or another, I receive a string of data and I start storing the data string at the middle instead of the beginning and miss some data. Here's what I have:

' Program to echo incoming serial data
' Baudrate : 2400 Bauds
' Method : Polling USART interrupts flags

' Pic Definition
' ==============
' Using PIC 18F2320 @ 4MHZ and bootloader
'
DEFINE LOADER_USED 1
DEFINE OSC 4

' Hardware configuration
' ======================
'
'
TRISC = %10000000 ' PORTC.7 is the RX input
' PORTC.6 is the TX output

' Serial communication definition
' ===============================
' Using internal USART and MAX232 to interface to PC
'
DEFINE HSER_RCSTA 90h ' enable serial port,
' enable continuous receive
'
define HSER_TXSTA 24h ' enable transmit,
' BRGH=1
'
define HSER_SPBRG 103 ' set baudrate to 2400
DEFINE HSER_CLOERR 1 ' automatic clear overrun error

' Alias definition
' ================
'
'
RCIF VAR PIR1.5 ' Receive interrupt flag (1=full , 0=empty)
TXIF VAR PIR1.4 ' Transmit interrupt flag (1=empty, 0=full)
a var byte
i var byte
' Variable definition
' ===================
'
'
SerialData var byte[40]

' Hardware initialisation
' =======================
'
'
pause 10 ' safe start-up delay

Main:
' Clear - tried using this to clear, but then I get nothing back

if RCIF then ' incomming data?
hserin [SerialData[0]] 'Store the first character received in SerialData,
'at byte 0
endif

if SerialData[0] = "!" then RCV 'if the first byte is an ASCII ! then
'go on to receive rest of data string


goto Main


RCV:

for i = 1 to 40

hserin [SerialData[i]] ' take it
if SerialData[i] = "L" then TRS 'if an ASCII L is
'present stop
'and output
'string
next

goto Main 'If ASCII L is not detected return to main loop


TRS:
for a = 1 to i 'Okay, if I set a = 0 to i, I get a ! in
'front of everything when it outputs
'i.e. if I send !#00CL I get !!#00CL
'back. Why, I don't know.
hserout [SerialData[a]] ' send it
next 'endif
hserout [10,13] 'line feed and carriage return
goto Main





Alright, if I send !#X00CL I get back !#X00CL, which is great! However, and here's the where the confusion starts, if I send 123456ABCDEF#, I get nothing back, again, good news right? But, if I follow that string with !#X00CL, I get back 123456ABCDEF#!#X00CL. I am hitting a wall here.

It seems as though the program stores up to 41 (0 to 40) bytes from a serial string (this because in my code I set SerialData to store up to 41 bytes, from 0 to 40). Once it sees 41 bytes, it resets itself and starts anew until it sees an ASCII L. For example, if I send 123456ABCDEF# three times then follow with !#X00CL I get back #1X00CL.

Is there a way to tell the program to write and erase to only SerialData[0] until a specific character is seen? ASCII ! in this case. Or am I missing something else altogether? Thanks!

[mister_e]

this should give you a hand!

    '   Program to echo incoming serial data 
    '   Baudrate : 2400 Bauds
    '   Method :   Polling USART interrupts flags

    '   Pic Definition
    '   ==============
        ' Using PIC 18F2320 @ 4MHZ and bootloader
        '
        DEFINE LOADER_USED 1
        DEFINE OSC 4
        
    '   Hardware configuration
    '   ======================
        '
        '
        TRISC  = %10000000    ' PORTC.7 is the RX input
                              ' PORTC.6 is the TX output
    
    '   Serial communication definition
    '   ===============================
        ' Using internal USART and MAX232 to interface to PC
        '
        RCSTA=$90 ' enable serial port, 
                  ' enable continuous receive
                  '
        TXSTA=$24 ' enable transmit, 
                  ' BRGH=1
                  '
        SPBRG=103 ' set baudrate to 2400                   
        DEFINE HSER_CLOERR   1 
        
    '   Alias definition
    '   ================
        '
        '
        RCIF VAR PIR1.5     ' Receive  interrupt flag (1=full , 0=empty)
        TXIF VAR PIR1.4     ' Transmit interrupt flag (1=empty, 0=full)
        CREN var RCSTA.4    ' Receiver enable bit
        
    '   Variable definition
    '   ===================
        '
        '
        SerialString var byte[40]
        Counter      var byte
        Success      var bit
        i            var byte
        
    '   Hardware initialisation
    '   =======================
        '
        '
        pause 100 ' safe start-up delay

Main:
   clear
   if RCIF then               ' incomming data?
      I=RCREG                 ' take it
      if i !="!" then discard ' is it the header character?
      Redo:
          hserin 500,discard,[i]  ' get next character, if it's too long
                                  ' get out of here and wait the next header
                                  ' character
                                  '
          if i ="L" then discard  ' is it the end?
          serialstring[counter]=i ' Store into the array
          counter=counter+1       '
          goto Redo      
      Discard:
              if i="L" then success=1 ' Yeah i got a valid string
      endif
  
   if success then
      cren=0  ' Disable Receiver
      hserout ["String received : ",str serialstring\counter,13,10,_
               "Character count : ", dec counter,13,10]
      cren=1  ' Enable receiver
      endif
   goto main

[elec_mech]

Steve,

Thank you for the code, it worked beautifully. I did notice that moving the clear command down to the very bottom right before the 'goto main' worked better. I think the data came in so fast that if the timing were off I missed some data streams.

I have a question regarding the clear command. I understand it completely clears the ram which prevents a constant repeating loop of a single data input stream. Is there another way to specifically clear or erase whatever register or ram location the USART uses? I ask because I am running several if then statements that require checking the status of certain variables and if I use the clear command, I lose the original status/data in those variables.

I've tried using RCIF = 0 and RCREG = 0 to no avail. I've also tried the ERASECODE $FAEh to clear the RCREG register, but this command doesn't work in PicBasic Pro with the 18F2525 chip I'm using. Any suggestions?

Again, thanks again for the code, I've been playing with it all day, making mistakes, gaining victories and generally learning a lot in the process.

[mister_e]

You're welcome.

You'll clear then RCREG by reading it 2 times

TempVar=RCREG
TempVar=RCREG