Emulate HSerReceive with SoftSerial

[Clint Koehn]

You can use a hardware interrupt to act as a hardware serial receive. Hook your TX from your device to a hardware interrupt. Set the edge detect to falling. Set that port/pin to SoftSerial RX. Set any other pin to SoftSerial TX.

This is with my new micro controller so it will probably need modying for your device, but I have used it on an older model that had hardware interrupts and it worked.

#chip 16f19176, 32

#include <SoftSerial.h>

'======= Simulate hardware rx ==============================
#define SER1_TXPORT PORTB
#define SER1_TXPIN 1
#define SER1_RXPORT PORTB 'needs to be a port and pin
#define SER1_RXPIN 0      'that is an interrupt
#define SER1_BAUD 9600
#define SerInPort1 PORTB.0
#define SerOutPort1 PORTB.1

'Set pin directions
dir SerOutPort1 Out
Dir SerInPort1 In

set SerOutPort1 on

#define SOFTWARE_BUFFER1 60

dim rxbuf1 as string * SOFTWARE_BUFFER1 'uses a string for a buffer
dim rxflag1 as Integer                  'flag to tell when new char

rxflag1 = 0
rxbuf1(0) = 0

INTEDG = 0 'Interrupt on falling edge

On Interrupt ExtInt0 Call Rx1Int
'===================================

do
    if rxflag1 = 1 Then  ' new character in buffer
        rxflag1 = 0         ' reset buffer flag
        '----- start char is ? and end char is CR -----------
        if (rxbuf1(1) = "?") and (rxbuf1(rxbuf1(0)) = 13) Then
              'complete message
               rxbuf1(1) = "!"   'change start char
               wait 500 us       'need brief delay before send 
               Ser1Print rxbuf1
                rxbuf1(0) = 0     'clear buffer
        end if
  end if    
loop

sub Rx1Int
    rxbuf1(0)++                            'inc char location
    rxbuf1(rxbuf1(0)) = Ser1Receive        'store char in string variable
    if rxbuf1(0) = SOFTWARE_BUFFER1 then   'if end of buffer
       rxbuf1(0) = 0                         '    start over
    end if
     rxflag1 = 1                            'set flag for new character
end sub

Later,
Clint

[Chris Roper]

Simple, Elegant and addresses the main downfall of SoftSerial.
I, and I am sure many others, will find this both useful and inspirational.
Thanks for sharing.

Cheers
Chris

[Clint Koehn]

Thanks for the kind words Chris. I have a chip that has 2 hardware serial ports but I needed a third one. One radio went to the computer, one was for a sensor board I made and I needed a third one for a 4D display.

Later,
Clint