Software USART routines (Alternate)

[kent_twt4]

Hopefully a bug will be removed soon which keeps the the 12f675, 12f683 type devices from currently working.  Using a terminal program like Bray's Terminal, or Smiley's Developer Terminal with a split send/receive screen is helpful.  Enjoy!!!

'This example uses alternate software UART/RS232 routines.
'The Pic is programmed to wait for a value to be sent from a
'terminal/computer, and will return an a2d value if the received
'value is a match.  All constants of SerInit need to be edited to suit
'device choice and baud rate.  At this time, the low pin count
'devices like the 12f675, 12C5XX are not supported.
'Kent Schafer 8/6/08
  
'Chip model
#chip 18f4620,8
#config MCLRE=ON, OSC=INTIO67, LVP=OFF
dim ADvalue as word
Ser_Init 
dir PortA.0 out
dir PortA.1 in

start:
Set PORTA.0 On
wait 1 s
Set PortA.0 off
wait 1 s
;Pic waits for signal from terminal/computer
RCV_RS232            ;Return value is RxByte
Bin2ascii RxByte    ;echo back received string/ascii value
XMIT_PRINT ("hello") 
If RxByte = 52 Then      ;ascii 52 (Decimal 4 from terminal)
    Bin2ascii ReadAD10(AN1)
End if   
XMIT_Print ("  ")
goto start 

Sub Ser_Init
;slight adjustment was required for 9600bps delay value 
#define baud 103
#define halfbaud 52    ;place Read of SerRx in middle of bit 
#define SerTxHigh Set PortC.6 On
#define SerTxLow Set PortC.6 Off
#define SerRx PortC.7
dir PortC.7 in    ;Rx
dir PortC.6 out    ;Tx 
SerTxHigh ;Initial RS232 idle state
end sub 

Sub RCV_RS232
RxWait:
IF SerRx On Then goto RCV_RS232  ;wait for start bit
wait halfbaud us              ;do half bit time delay
If SerRx On Then goto RxWait
RxByte = 0
For RxBit = 1 to 8                ;set up to read 8 bits
wait baud us
Rotate RxByte Right
If SerRx On then Set RxByte.7 1
If SerRx Off Then Set RxByte.7 0
Next
wait baud us
End sub

sub XMIT_PRINT (PrintData$) 
PrintLen = PrintData(0) 
if PrintLen = 0 then exit sub 
'Write Data 
for SysPrintTemp = 1 to PrintLen 
XMIT_RS232(PrintData(SysPrintTemp)) 
next 
end sub 

Sub XMIT_RS232(Xmit_Byte)#NR 
SerTxLow
wait baud us 
For cntr = 1 to 8 
Rotate Xmit_Byte Right 
If Status.C ON Then SerTxHigh
If Status.C Off Then SerTxLow
wait baud us
Next 
SerTxHigh
wait baud us 
end sub 

sub Bin2ascii(LCDValue as word )#NR
dim LCDValueTemp as word 
SERDECMIL = 0
SERMIL = 0
SERCEN = 0
SERDEC = 0
SERUN = 0
LCDValueTemp = 0
IF LCDValue >= 10000 then
LCDValueTemp = LCDValue / 10000
SERDECMIL = LCDValueTemp + 48
Xmit_RS232(SERDECMIL) 'SerSend (1,SERDECMIL)
LCDValue = LCDValue - LCDValueTemp * 10000
End if
If LCDValueTemp > 0 Or LCDValue >= 1000 Then
LCDValueTemp = LCDValue / 1000
SERMIL = LCDValueTemp + 48
Xmit_RS232(SERMIL) 'SerSend (1,SERMIL)
LCDValue = LCDValue - LCDValueTemp * 1000
End if
IF LCDValueTemp > 0 OR LCDValue >= 100 then  
LCDValueTemp = LCDValue / 100
SERCEN = LCDValueTemp + 48 
Xmit_RS232(SerCen) 'SerSend (1,SERCEN) 
LCDValue = LCDValue - LCDValueTemp * 100 
end if 
IF LCDValueTemp > 0 OR LCDValue >= 10 then 
LCDValueTemp = LCDValue / 10  
SERDEC = LCDValueTemp + 48 
Xmit_RS232(Serdec) 'SerSend (1,SERDEC) 
LCDValue = LCDValue - LCDValueTemp * 10 
end if 
SERUN = LCDValue + 48 
Xmit_RS232(Serun) 'SerSend (1,SERUN) 
end sub 

[Nobody/Anonymous]

For inverted output:

Sub RCV_RS232
    RxWait:
    IF SerRx Off then
        goto RCV_RS232 ;wait for start bit
    end if
    wait halfbaud us ;do half bit time delay
    If SerRx Off then
        goto RxWait
    end if
    RxByte = 0
    For RxBit = 1 to 8 ;set up to read 8 bits
        wait baud us
        Rotate RxByte Right
        If SerRx On then
            Set RxByte.7 0
        end if
        If SerRx Off then
            Set RxByte.7 1
        end if
    Next
    wait baud us
End Sub

Changed:

If SerRx Off Then [line 3&5]
Set RxByte.7 0/1 [line 15&19]

[Nobody/Anonymous]

Sorry, unconsciously modified and saved these lines,
This line should be changed for inverted output.

#define SerTxHigh Set PortB.5 Off
#define SerTxLow Set PortB.5 On