RS232 Software letal bug solved

[Erdy]

http://fr.wikipedia.org/wiki/UART (in french, the english version is different and less clear)

RS232 Software TX has one BIG letal bug.
The sleep, idle, no signal state of an RS232 TX line is ON / 1 / Vdd
The Start Bit is a 0
The Stop Bit is a 1

GCBASIC RS232 Software is all wrong on these
This can be solved by changing two lines in rs232.h

line 157 : start bit SerTxLow ' instead of SerTxHigh
line 184 : stop bit SerTxHigh ' instead of SerTxLow

With these two changes, my PC receives correctly my PIC16F628A with it's internal 4MHz clock up to 4800 baud, on an USB RS232 TTL using prolific It must be the same on RX side ???? …

see also messages in Great Cow Graphical Forum

I am proud of me :-)

[Erdy]

And here is the RX fix
In gcbasic/include/lowlevel/rs232.h modify the followinglines

line 200
Wait Until SerQuickSample = False ' instead of Wait Until  = TRUE

line 202
If SerQuickSample = True Then Exit Sub ' instead of  If SerQuickSample = False Then Exit Sub

line  238 to 243
        must be uncommented   :-)

line 243
Wait Until SerQuickSample = True      ' instead of  Wait Until SerQuickSample = FALSE

With these changes, PIC16F628A with it's internal 4MHz clock receives my PC up to 2400 baud, on an USB RS232 TTL using prolific

---

other things :

There must be an error in Delays as someone told me in an other forum here,  when the 4MHz INT OSC of the PIC in replaced by a 20 MHz cristal, the maximum baud rate received by the PC does not change. I don't understand how the time delay is computed ????

On the Sub SerSend side shouldn't there be an IntOff/IntOn too ?

[Erdy]

Oops ! With a 20 MHz cristal ext osc, tha maximum TX speed is 19200 baud and the maximum RX speed is 4800 baud with the PC ! Using the corrected rs232.h

Why 4800 only for RX ???

[Erdy]

Codes
gcbasic RX/TX  Hard/Soft  RS232 INT OSC/EXT OSC  FAST/SLOW Soft RS232  Code

' ==============================================================
' TEST CODE
' PIC16F628A RX/TX, Hardware/Software RS232,  OSC INT/EXT
' Two Speed  fast/Slow for RS232 Software on jumper, need reset
' RX/TX on Jumper need reset
' Test Materials :
' Windows, INT OSC/20MHz EXT OSC, PIC on Prolific-USB-Serial-Com, GCBASIC 0.9
' RS232 to USB TTL interface, no MAX232 required
' Erdemal                                        March 1st, 2013
' ==============================================================
' input PortA.0  (10k pulled up) sets   RX/TX mode    RX if ON = no Jumper,
'                 TX if OFF = Jumper to Vss
' input PortA.1  (10k pulled up) sets   High/Low baud rate only for RS232 Software 
'                Low Baud Rate = ON = no jumper,  high Baud rate = Off = Jumper to Vss
'
' TX mode   on PortB.2     alternativly sends 50 then 100 every 200 ms
'           Led on TX to Vdd via 4.8K (to see data flow)
' -------
' RX mode   on PortB.1
' -------
' output PortB.4  ON >> LED GREEN  ON    In RX mode ON when 100 is received
' output PortB.5  ON >> LED RED    ON    In RX mode ON when neither
'                                        50 nor 100 is received (= RX error)
' Output PortB.6  ON >> LED YELLOW ON    In RX Mode ON when  50 is received
' (50 and 100 choosen for no good/bad reason)
' RX OK when flashing Green/Yellow, if RX error LedRed is on
' --------------------------------------------------------------
' ISSUE
' - In GCBASIC RS232 software with PIC transmitting to PC, RX data is always Halve the TXed value.
'   It looks like the 8th bit is not sent or the first bit is the last start bit ??????????
'   When two PIC communicate together with GCBASIC RS232 software, it works up to 4800 bauds
' - partly solved, still a Delay error
'   https://sourceforge.net/projects/gcbasic/forums/forum/596084/topic/6877271/index/page/1
' --------------------------------------------------------------
' With GCBASIC RS232 Hardware communication with a computer it works perfectly
'  - up to 19200 bauds with 16F628A 4MHz Osc Int +-1.5%
'  - with a 20 MHz EXT OSC quartz 57600 baud obtained
' ==============================================================
#Define OscQuartz       ' not sure these works in gcbasic
#Define SerialHardware  ' if not, comment the lines
' ==============================================================
#IfNDef OscQuartz ' ++++++++++++++++++++++++++++++++++++++++++++
#chip 16F628A, 4
#EndIf ' +++++++++++++++++++++++++++++++++++++++++++++++++++++++
'
#IfDef OscQuartz ' +++++++++++++++++++++++++++++++++++++++++++++
#Chip 16F628A, 20
#EndIf ' +++++++++++++++++++++++++++++++++++++++++++++++++++++++
' --------------
#config MCLR_OFF
' ==============================================================
' - Jumpers -    No Jumper : RX and 4800 bds
' -----------
#Define btnRXTX PortA.0  ' On RX   , Off/0v = TX   = jumper placed
#Define btn4896 PortA.1  ' On 4800 , Off/0v = 9600 = jumper placed
'
Dir btnRXTX in
Dir btn4896 in
' ==============================================================
#IfDef SerialHardware ' ++++++++++++++++++++++++++++++++++++++++
#Define USART_BAUD_RATE 9600
#EndIf ' +++++++++++++++++++++++++++++++++++++++++++++++++++++++
' ==============================================================
#IfnDef SerialHardware ' +++++++++++++++++++++++++++++++++++++++
' - Init TX -
#define SendAHigh Set PORTB.2 ON    ' MUST LINES
#define SendALow Set PORTB.2 OFF    ' MUST LINES
'
Dir PORTB.2 Out
' ---------------------------
' - Init RX  -
#define RecAHigh PORTB.1 ON         ' MUST LINES
#define RecALow PORTB.1 OFF         ' MUST LINES
'
Dir PORTB.1 In
#EndIF   ' ++++++++++++++++++++++++++++++++++++++++++++++++++++++
'
#define LedGreen  PORTB.4
#define LedRed    PORTB.5
#define LedYellow PORTB.6
'
Dir PORTB.4 Out
Dir PORTB.5 Out
Dir PORTB.6 Out
'
' ==============================================================
' ---- Select  RX or TX ----
' --------------------------
Select Case btnRXTX
    Case Off
        Goto DataTransmitter
    Case On
        Goto DataReceiver
    Case Else
End Select
' ==============================================================
' ---- Transmitter ----    
' ---------------------
DataTransmitter:
'
#IfnDef SerialHardware
If btn4896 = On Then
    InitSer 1, r9600, 1+WaitForStart, 8, 1, none, normal
Else
    InitSer 1, r19200, 1+WaitForStart, 8, 1, none, normal
End If
#EndIf
'
Do  ' just flash yellow green for OK and RED for junks
    If Temp = 100 Then
        Temp = 50
        Else
        Temp = 100
    End If
    #IfnDef SerialHardware ' +++++++++++++++++++++++++++++++++++
        SerSend 1, Temp     ' TX remains OFF after transfer
    #EndIf ' +++++++++++++++++++++++++++++++++++++++++++++++++++
    #IfDef SerialHardware
        HSerSend Temp       ' TX remains ON after transfer
    #EndIf
    Wait 20 10ms
Loop
'
' ==============================================================
' ---- Receiver ----
' ------------------
DataReceiver:
'
set LedGreen off
set LedRed off
set LedYellow off
'
#IfnDef SerialHardware
If btn4896 = On Then
    InitSer 1, r9600, 129, 8, 1, none, normal
Else
    InitSer 1, r19200, 129, 8, 1, none, normal
End If
#EndIf
'
Do  ' just flash yellow (RX=50) green(RX=100) and RED for junks (RX Else)
    #IfnDef SerialHardware  ' ++++++++++++++++++++++++++++++++++++
        SerReceive 1, Temp
    #EndIf ' +++++++++++++++++++++++++++++++++++++++++++++++++++++
    #IfDef SerialHardware ' ++++++++++++++++++++++++++++++++++++++
        HserReceive Temp
    #EndIf ' +++++++++++++++++++++++++++++++++++++++++++++++++++++

    Select Case Temp
        Case 50
            Set LedYellow On 
            Set LedGreen Off
            Set LedRed Off      
        Case 100
            Set LedGreen On
            Set LedYellow Off 
            Set LedRed Off      
        Case Else
            Set LedRed on
            Set LedYellow Off 
            Set LedGreen Off 
    End Select
Loop
' ==============================================================
'

FREEBASIC  RS232   RX   CODE

' =========================================================
' FREEBASIC RS232 TX TEST CODE
' targetted on gcbasic rs232 with PIC controller
' Erdemal                                     March 2, 2013
' =========================================================
'
#include once "windows.bi"
'
Dim As Integer iCom, iFile
Dim sCom As String
iFile = FreeFile
'
sCom = "COM6:19200,N,8,1,cs0,ds0,cd0,rs"        ' Change ComX and Speed here
' Open Com sCom As iFile
iCom = Open Com (sCom, As iFile)
If iCom = 0 Then
    Print "OPEN COM OK   Returns 0"
Else
    MessageBox (0, "ERROR OPEN COM FAILED, I CLOSE", "GCBASIC RS232 RX TEST", 0)
    End   
End If
'
Dim As Byte J, K
Dim N As integer
J = 100
K = 50
For N = 0 To 10
     Sleep 200
     Print #ifile, Chr(J);    ' ; no CR sent
     Sleep 200
     Print #ifile, Chr(K);    ' ; no CR sent
Next N
'
Print
Print "    **** FINISHED ****"
'
Close iFile
Sleep
' =========================================================

' =========================================================
' FREEBASIC RS232 RX TEST CODE
' targetted on gcbasic rs232 with PIC controller
' Erdemal                                     March 2, 2013
' =========================================================
'
#include once "windows.bi"
'
Dim As Integer iCom, iFile, iCount = 0
Dim sCom As String
iFile = FreeFile
'
sCom = "COM6:9600,N,8,1,cs0,ds0,cd0,rs"        ' Change  ComX and Speed here
' Open Com sCom As iFile
iCom = Open Com (sCom, As iFile)
If iCom = 0 Then
    Print "OPEN COM OK   Returns 0"
Else
    MessageBox (0, "ERROR OPEN COM FAILED, I CLOSE", "GCBASIC RS232 RX TEST", 0)
    End   
End If
'
Dim bData As uByte
'
bData = 0
Messagebox (0, "CLOSE TO START RS232 RX", "Jack", 0)
'
iCount = 0
Get #iFile, , bData
While icount < 20
    If bData <> 0 Then
        Print bData
        iCount = iCount + 1
    End If
    bdata = 0
    Sleep 10
    Get #iFile, , bData    
Wend
'
Print
Print "    **** FINISHED ****"
'
Close iFile
Sleep'

Great SourceForge deserves better forums :-)

Erdemal

[ic-beau]

RS232 is normally inverted…  IOW… so lines 157 and 184 are correct.  Same with the data it's also supposed to be inverted.

As far as the baud speed, I'm not sure about how GCB compiler does it because I was using a PIC that wasn't fully supported.  So I had to roll my own in-line assembly bit-banging the serial routines.  On a PIC16F54 I was able to get 57,600 baud running at 20MHz

Reference:
http://en.wikipedia.org/wiki/File:Rs232_oscilloscope_trace.svg

[Erdy]

I don't know whose source is the good one ?
- the PIC Rs232 Hardware works as my source
- the gcbasic RS232 Software samples don't work in my real world

[Anobium]

I have looked into this issue. My results. I have tested and this now makes sense to me....

See the revised rs232.h, see below (I cannot attach!!). This is adapted as per @Erdy great insights.

I have wrapped these with a #define to ensure I can choose whether I want to communicate with a PC or an IC.

General Rules...

For a PC. I am using the new define statement and 'normal'. Therefore, I use '#define RS232ForPC' and a command similar to InitSer 1, r4800, 1+WaitForStart , 8, 1, none, normal

For an IC. Do add the define statement and use 'invert'. Therefore, I would simply use 'a command similar to InitSer 1, r4800, 1+WaitForStart , 8, 1, none, invert

RS232.H

' Serial/RS232 routines for Great Cow BASIC
' Copyright (C) 2006 Hugh Considine

' This library is free software; you can redistribute it and/or
' modify it under the terms of the GNU Lesser General Public
' License as published by the Free Software Foundation; either
' version 2.1 of the License, or (at your option) any later version.

' This library is distributed in the hope that it will be useful,
' but WITHOUT ANY WARRANTY; without even the implied warranty of
' MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
' Lesser General Public License for more details.

' You should have received a copy of the GNU Lesser General Public
' License along with this library; if not, write to the Free Software
' Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA

'***********
'IMPORTANT:
'THIS FILE IS ESSENTIAL FOR SOME OF THE COMMANDS IN GCBASIC. DO NOT ALTER THIS FILE
'UNLESS YOU KNOW WHAT YOU ARE DOING. CHANGING THIS FILE COULD RENDER SOME GCBASIC
'COMMANDS UNUSABLE!
'***********

'Usage of Sys232Temp
'Bit Use
'0 Dummy receive source
'1 Receive buffer

'I/O command defines
'Note: These all default to dummy ports and MUST BE CHANGED PRIOR TO USE
'#define SendALow nop
'#define SendAHigh nop
'#define RecALow Sys232Temp.0 OFF
'#define RecAHigh Sys232Temp.0 ON
'#define SendBLow nop
'#define SendBHigh nop
'#define RecBLow Sys232Temp.0 OFF
'#define RecBHigh Sys232Temp.0 ON
'#define SendCLow nop
'#define SendCHigh nop
'#define RecCLow Sys232Temp.0 OFF
'#define RecCHigh Sys232Temp.0 ON

'Assign values to key words

'Parity
#define none 0
#define odd 1
#define even 2

'Signal Inversion
#define normal 0
#define invert 1

'Start Bit settings
#define WaitForStart 128

'Bit rate delays
'Moved to stdbasic.h
'r* is us delay/52 for 1 bit

'Calculate delay lengths
#script
If PIC Then
'20 MHz PIC, 7 us taken off - 35 instructions
SerThirdDelay19200 = int(17 - 4 / ChipMHz * 35)
SerThirdDelay9600 = int(35 - 4 / ChipMHz * 35)
SerThirdDelay4800 = int(69 - 4 / ChipMHz * 35)
SerThirdDelay2400 = int(139 - 4 / ChipMHz * 35)
SerThirdDelay1200 = int(278 - 4 / ChipMHz * 35)
SerThirdDelay600 = int(555 - 4 / ChipMHz * 35)
SerThirdDelay300 = int(1111 - 4 / ChipMHz * 35)

                  '20 MHz PIC, 10 us taken off - 50 instructions
                  SerFullDelay19200 = int(52 - 4 / ChipMHz * 45)
                  SerFullDelay9600 = int(104 - 4 / ChipMHz * 50)
                  SerFullDelay4800 = int(208 - 4 / ChipMHz * 50)
                  SerFullDelay2400 = int(417 - 4 / ChipMHz * 50)
                  SerFullDelay1200 = int(833 - 4 / ChipMHz * 50)
                  SerFullDelay600 = int(1666 - 4 / ChipMHz * 50)
                  SerFullDelay300 = int(3333 - 4 / ChipMHz * 50)
        End If
        If AVR Then
                  '1 MHz AVR, 60 us taken off - 60 instructions
                  SerThirdDelay19200 = int(17 - 1 / ChipMHz * 60)
                  SerThirdDelay9600 = int(35 - 1 / ChipMHz * 60)
                  SerThirdDelay4800 = int(69 - 1 / ChipMHz * 60)
                  SerThirdDelay2400 = int(139 - 1 / ChipMHz * 60)
                  SerThirdDelay1200 = int(278 - 1 / ChipMHz * 60)
                  SerThirdDelay600 = int(555 - 1 / ChipMHz * 60)
                  SerThirdDelay300 = int(1111 - 1 / ChipMHz * 60)

                  '1 MHz AVR, 67 us taken off - 67 instructions
                  SerFullDelay19200 = int(52 - 1 / ChipMHz * 67)
                  SerFullDelay9600 = int(104 - 1 / ChipMHz * 67)
                  SerFullDelay4800 = int(208 - 1 / ChipMHz * 67)
                  SerFullDelay2400 = int(417 - 1 / ChipMHz * 67)
                  SerFullDelay1200 = int(833 - 1 / ChipMHz * 67)
                  SerFullDelay600 = int(1666 - 1 / ChipMHz * 67)
                  SerFullDelay300 = int(3333 - 1 / ChipMHz * 67)
        End If

#endscript

'Serial receive buffer
#define SerRxData Sys232Temp.1

sub InitSer(In Ser_Select, In Ser_Rate, In Ser_Start, In Ser_Data, In Ser_Stop, In Ser_Parity, In Ser_Invert)
'This sub sets configuration of the serial routines
'Sample usage for communication with Lego RCX:
'InitSer(1,r2400,1,8,1,odd,invert)

        Ser_Select_Old = Ser_Select

        #ifdef OneOf(SendAHigh, RecAHigh)
                  if Ser_Select = 1 THEN
                            Ser_Rate_A = Ser_Rate
                            Ser_Start_A = Ser_Start
                            Ser_Data_A = Ser_Data
                            Ser_Stop_A = Ser_Stop
                            Ser_Parity_A = Ser_Parity
                            Ser_Invert_A = Ser_Invert
                  END IF
        #ENDIF

        #ifdef OneOf(SendBHigh, RecBHigh)
                  if Ser_Select = 2 THEN
                            Ser_Rate_B = Ser_Rate
                            Ser_Start_B = Ser_Start
                            Ser_Data_B = Ser_Data
                            Ser_Stop_B = Ser_Stop
                            Ser_Parity_B = Ser_Parity
                            Ser_Invert_B = Ser_Invert
                  END IF
        #ENDIF

        #ifdef OneOf(SendCHigh, RecCHigh)
                  if Ser_Select = 3 THEN
                            Ser_Rate_C = Ser_Rate
                            Ser_Start_C = Ser_Start
                            Ser_Data_C = Ser_Data
                            Ser_Stop_C = Ser_Stop
                            Ser_Parity_C = Ser_Parity
                            Ser_Invert_C = Ser_Invert
                  END IF
        #ENDIF

end sub

Sub SerSend(In Ser_Select, In Ser_Byte)

        'Load configuration data
        if Ser_Select <> Ser_Select_Old then SerCfgLoad(Ser_Select)

        'Start
        SerTemp = Ser_Start and (not WaitForStart)
        for SerBit = 1 to SerTemp
            #ifndef RS232ForPC
                  SerTxHigh
            #endif
            #ifdef RS232ForPC
                  SerTxlow
            #endif
        next

        'Data
        TempParity = SerTemp
        for SerBit = 1 to Ser_Data
                  if Ser_Invert = normal then
                            if Ser_Byte.0 ON then SerTxHigh: TempParity = TempParity + 1
                            if Ser_Byte.0 OFF then SerTxLow
                  end if
                  if Ser_Invert = invert then
                            if Ser_Byte.0 ON then SerTxLow: TempParity = TempParity + 1
                            if Ser_Byte.0 OFF then SerTxHigh
                  end if
                  rotate Ser_Byte right
        next

        'Parity
        if Ser_Parity <> 0 THEN
                  if Ser_Parity = odd then TempParity = TempParity + 1
                  if Ser_Invert = invert then TempParity = TempParity + 1
                  if TempParity.0 = ON then SerTxLow
                  if TempParity.0 = OFF then SerTxHigh
        end if

        'End
        for SerBit = 1 to Ser_Stop
            #ifndef RS232ForPC
                  SerTxLow
            #endif
            #ifdef RS232ForPC
                  SerTxHigh
            #endif
        next

        'Extra delay at end
        SerBitDelay

end sub

Sub SerReceive(In Ser_Select, Out Ser_Byte)

        'Load configuration data
        if Ser_Select <> Ser_Select_Old then SerCfgLoad(Ser_Select)

        'Receive start bit/s
        'If Ser_Start.7 is on then wait, otherwise exit if there's no signal
        If Ser_Start.7 = On Then
                  Wait Until SerQuickSample = TRUE
        Else
                  If SerQuickSample = False Then Exit Sub
        End If

        'Disable interrupts
        IntOff

        'Get start bits
        SerTemp = Ser_Start and (not WaitForStart)
        for SerBit = 1 to SerTemp
                  SerRxBit
        next

        'Receive data byte
        Ser_Byte = 0
        for SerBit = 1 to Ser_Data
                  SerRxBit
                  Rotate Ser_Byte Right
        next
        'Add any missing bits
        if Ser_Data < 8 then
                  'SerTemp = 8 - Ser_Data
                  for SerBit = Ser_Data to 8
                            Set C Off
                            ROTATE Ser_Byte RIGHT
                  next
        end if
        if Ser_Invert = invert then Ser_Byte = !Ser_Byte

        'Receive parity
        if Ser_Parity <> 0 THEN
                  TempParity = 0
                  SerRxBit
        end if

        'Receive stop bit/s
        'if Ser_Start.7 on then wait until SerQuickSample = FALSE
        'if Ser_Start.7 off then
        '   for Bit = 1 to Ser_Stop
        '       SerRxBit
        '   next
        'end if
        Wait Until SerQuickSample = FALSE

        'Re-enable interrupt
        IntOn

end sub

sub SerPrint (In Ser_Select, PrintData As String)
'PrintLen = LEN(PrintData$)
PrintLen = PrintData(0)

        if PrintLen = 0 then Goto SerPrintStrEnd

        'Write Data
        for SysPrintTemp = 1 to PrintLen
                  SerSend(Ser_Select, PrintData(SysPrintTemp))
        next

        'CR
        SerPrintStrEnd:
        #IFDEF SerPrintCR
                  SerSend(Ser_Select, 13)
        #ENDIF
        #IFDEF SerPrintLF
                  SerSend(Ser_Select, 10)
        #ENDIF

end sub

sub SerPrint (In Ser_Select, In SerPrintVal)

        OutValueTemp = 0

        IF SerPrintVal >= 100 Then
                  OutValueTemp = SerPrintVal / 100
                  SerPrintVal = SysCalcTempX
                  SerSend(Ser_Select, OutValueTemp + 48)
        End If
        If OutValueTemp > 0 Or SerPrintVal >= 10 Then
                  OutValueTemp = SerPrintVal / 10
                  SerPrintVal = SysCalcTempX
                  SerSend(Ser_Select, OutValueTemp + 48)
        End If
        SerSend(Ser_Select, SerPrintVal + 48)

        'CR
        #IFDEF SerPrintCR
                  SerSend(Ser_Select, 13)
        #ENDIF
        #IFDEF SerPrintLF
                  SerSend(Ser_Select, 10)
        #ENDIF

end sub

Sub SerPrint (In Ser_Select, In SerPrintVal As Word)
Dim SysCalcTempX As Word

        OutValueTemp = 0

        If SerPrintVal >= 10000 then
                  OutValueTemp = SerPrintVal / 10000 [word]
                  SerPrintVal = SysCalcTempX
                  SerSend(Ser_Select, OutValueTemp + 48)
                  Goto SerPrintWord1000
        End If

        If SerPrintVal >= 1000 then
        SerPrintWord1000:
                  OutValueTemp = SerPrintVal / 1000 [word]
                  SerPrintVal = SysCalcTempX
                  SerSend(Ser_Select, OutValueTemp + 48)
                  Goto SerPrintWord100
        End If

        If SerPrintVal >= 100 then
        SerPrintWord100:
                  OutValueTemp = SerPrintVal / 100 [word]
                  SerPrintVal = SysCalcTempX
                  SerSend(Ser_Select, OutValueTemp + 48)
                  Goto SerPrintWord10:
        End If

        If SerPrintVal >= 10 then
        SerPrintWord10:
                  OutValueTemp = SerPrintVal / 10 [word]
                  SerPrintVal = SysCalcTempX
                  SerSend(Ser_Select, OutValueTemp + 48)
        End If

        SerSend(Ser_Select, SerPrintVal + 48)

        'CR
        #IFDEF SerPrintCR
                  SerSend(Ser_Select, 13)
        #ENDIF
        #IFDEF SerPrintLF
                  SerSend(Ser_Select, 10)
        #ENDIF

End Sub

'Note: When calling this sub, set Ser_Select and Ser_Rate, and read carry bit
sub SerRxBit
'Clear bit counters
RxHighCount = 0

        'Read Port
        #ifdef OneOf(SendAHigh, RecAHigh)
                  if Ser_Select = 1 THEN
                            for SerBitSample = 1 to 3
                                      if RecAHigh then RxHighCount = RxHighCount + 1
                                      SerThirdBitDelay
                            next
                  end if
        #endif
        #ifdef OneOf(SendBHigh, RecBHigh)
                  if Ser_Select = 2 THEN
                            for SerBitSample = 1 to 3
                                      if RecBHigh then RxHighCount = RxHighCount + 1
                                      SerThirdBitDelay
                            next
                  end if
        #endif
        #ifdef OneOf(SendCHigh, RecCHigh)
                  if Ser_Select = 3 THEN
                            for SerBitSample = 1 to 3
                                      if RecCHigh then RxHighCount = RxHighCount + 1
                                      SerThirdBitDelay
                            next
                  end if
        #ENDIF

        'Decide whether received bit is 0 or 1, based on bit counters
        SET C OFF
        If RxHighCount.1 = ON Then SET C ON

end sub

Macro SerTxHigh
#ifdef SendAHigh
if Ser_Select = 1 THEN SendAHigh
#endif
#ifdef SendBHigh
if Ser_Select = 2 THEN SendBHigh
#ENDIF
#ifdef SendCHigh
if Ser_Select = 3 THEN SendCHigh
#ENDIF
SerBitDelay
End Macro

Macro SerTxLow
#ifdef SendALow
if Ser_Select = 1 THEN SendALow
#endif
#ifdef SendBLow
if Ser_Select = 2 THEN SendBLow
#ENDIF
#ifdef SendCLow
if Ser_Select = 3 THEN SendCLow
#ENDIF
SerBitDelay
End Macro

function SerQuickSample
SerQuickSample = FALSE

        'Read Port
        #ifdef OneOf(RecAHigh)
                  if Ser_Select = 1 THEN
                            if RecAHigh then SerQuickSample = TRUE
                  end if
        #endif
        #ifdef OneOf(RecBHigh)
                  if Ser_Select = 2 THEN
                            if RecBHigh then SerQuickSample = TRUE
                  end if
        #ENDIF
        #ifdef OneOf(RecCHigh)
                  if Ser_Select = 3 THEN
                            if RecCHigh then SerQuickSample = TRUE
                  end if
        #ENDIF

end function

sub SerCfgLoad(Ser_Select) #NR
Ser_Select_Old = Ser_Select

#ifdef OneOf(SendAHigh, RecAHigh)
if Ser_Select = 1 THEN
Ser_Rate = Ser_Rate_A
Ser_Start = Ser_Start_A
Ser_Data = Ser_Data_A
Ser_Stop = Ser_Stop_A
Ser_Parity = Ser_Parity_A
Ser_Invert = Ser_Invert_A
end if
#endif
#ifdef OneOf(SendBHigh, RecBHigh)
if Ser_Select = 2 THEN
Ser_Rate = Ser_Rate_B
Ser_Start = Ser_Start_B
Ser_Data = Ser_Data_B
Ser_Stop = Ser_Stop_B
Ser_Parity = Ser_Parity_B
Ser_Invert = Ser_Invert_B
end if
#ENDIF
#ifdef OneOf(SendCHigh, RecCHigh)
if Ser_Select = 3 THEN
Ser_Rate = Ser_Rate_C
Ser_Start = Ser_Start_C
Ser_Data = Ser_Data_C
Ser_Stop = Ser_Stop_C
Ser_Parity = Ser_Parity_C
Ser_Invert = Ser_Invert_C
end if
#ENDIF
end sub

sub SerBitDelay
'Predefined rates (more accurate)
'All delays have 10 us taken off to allow processing time
if Ser_Rate = 1 then Wait SerFullDelay19200 us: exit sub '19200 (52 us)
if Ser_Rate = 2 then Wait SerFullDelay9600 us: exit sub '9600 (104 us)
if Ser_Rate = 4 then Wait SerFullDelay4800 us: exit sub '4800 (208 us)
if Ser_Rate = 8 then Wait SerFullDelay2400 us: exit sub '2400 (417 us)
if Ser_Rate = 16 then Wait SerFullDelay1200 us: exit sub '1200 (833 us)
if Ser_Rate = 32 then Wait SerFullDelay600 us: exit sub '600 (1666 us)
if Ser_Rate = 64 then Wait SerFullDelay300 us: exit sub '300 (3333 us)

        'Other rates
        for SerDelayLoop = 1 to Ser_Rate
                  Wait 42 us
        next

end sub

sub SerThirdBitDelay
'Predefined rates (more accurate)
if Ser_Rate = 1 then Wait SerThirdDelay19200 us: exit sub '19200 (17 us)
if Ser_Rate = 2 then Wait SerThirdDelay9600 us: exit sub '9600 (35 us)
if Ser_Rate = 4 then Wait SerThirdDelay4800 us: exit sub '4800 (69 us)
if Ser_Rate = 8 then Wait SerThirdDelay2400 us: exit sub '2400 (139 us)
if Ser_Rate = 16 then Wait SerThirdDelay1200 us: exit sub '1200 (278 us)
if Ser_Rate = 32 then Wait SerThirdDelay600 us: exit sub '600 (555 us)
if Ser_Rate = 64 then Wait SerThirdDelay300 us: exit sub '300 (1111 us)

        'Other rates
        for SerDelayLoop = 1 to Ser_Rate
                  Wait 13 us
        next

end sub

[Chuck Hellebuyck]

This was a great post that looks like it has fixed a bug.
I've had issues with RS232 to PC communication that I couldn't figure out and this appears to fix it (though I still have to fully test it on my setup).

So will this be part of a future GCB update if this fixes an issue?

[Anobium]

In reality... it is not needed. As you can do everything with the standard code base.

With this patch I do not have to keep changing my code to much. I do and have got really confused with setting bits ON and OFF etc.

At least with this method... I 'define' the PC as my terminal device and then just change to 'normal'. It sort of makes sense to me.

:-)

[Max]

I got the same problem of Erdy (using TX/RX from software serial) after many test I made the modification on RS232.H suggested from Erdy/Anobium in this thread and now it work properly.
I should made another modification on RS232.H because the first char received was always corrupped.

this is the other fix on the RS232.H (by Anobyum) that i made for eliminate first corrupped received char

    #ifdef OneOf(SendAHigh, RecAHigh)
              SendAHigh                <----- insert this line
              if Ser_Select = 1 THEN

    #ifdef OneOf(SendBHigh, RecBHigh)
              SendBHigh                <----- insert this line
              if Ser_Select = 2 THEN

    #ifdef OneOf(SendCHigh, RecCHigh)
              SendCHigh                <----- insert this line
              if Ser_Select = 3 THEN

This is the test code (it does't work with the original RS232.H ... please you test also)

---

#chip 16F876A,20
#config OSC=HS

#define RS232ForPC     <------------

#define SerInPort PORTC.4
#define SerOutPort PORTC.5
#define SendAHigh Set SerOutPort On
#define SendALow Set SerOutPort off
#define RecAHigh SerInPort on
#define RecALow SerInPort off

Dir SerOutPort Out
Dir SerInPort In

'doesn't work more than baud 9600
InitSer 1, r9600, 1+WaitForStart, 8, 1, None, normal

inizio:
   SerReceive (1, Temp)
   sersend (1, Temp)
goto inizio

---

I am compiling with synwrite 6.1.140 & Great Cow BASIC (0.9 22/9/2013)
the USB serial cable is Prolific