Interrupting with SoftwareSerial on Arduino

Question

I'm using Bluetooth serial port profile to communicate with Arduino. The bluetooth module (HC-06) is connected to my digital pins 10 and 11 (RX, TX). The module is working properly, but I need an interrupt on data receive. I can't periodically check for incoming data as Arduino is working on a time-sensitive task (music-playing through a passive buzzer) and I need control signals to interrupt immediately on receive. I've looked through many documents including Arduino's own site, and they all explain how to establish regular communication using checking for serialPort.available() periodically. I've found one SO question Arduino Serial Interrupts but that's too complicated for my level. Any suggestions on reading realtime input through serial?

@IgnacioVazquez-Abrams Thanks for the extremely helpful response. — Can Poyrazoğlu
playground.arduino.cc/Main/PcInt Do I have to do everything for you? :P — Ignacio Vazquez-Abrams
@IgnacioVazquez-Abrams Okay, this would be a good starting point for me. — Can Poyrazoğlu

mpflaga mpflaga · Accepted Answer · 2014-08-04T15:14:53

Note that the current version of SoftSerial actually uses PCINT to detect the individual bits. Hence I believe defining it again at the main loop would conflict with the SoftSerial's actual detection of bits.

I am reluctant to suggest this as it is modifying a core library. Which is difficult not to do when sharing interrupts. But if desperate, you could modify that routine, with your need.

within

\arduino-1.5.7\hardware\arduino\avr\libraries\SoftwareSerial\SoftwareSerial.cpp.

//
// The receive routine called by the interrupt handler
//
void SoftwareSerial::recv()
{
...
    // if buffer full, set the overflow flag and return
    if ((_receive_buffer_tail + 1) % _SS_MAX_RX_BUFF != _receive_buffer_head) 
    {
      // save new data in buffer: tail points to where byte goes
      _receive_buffer[_receive_buffer_tail] = d; // save new byte
      _receive_buffer_tail = (_receive_buffer_tail + 1) % _SS_MAX_RX_BUFF;
#ifdef YOUR_THING_ENABLE
      // Quickly check if it is what you want and DO YOUR THING HERE!
#endif
    } 
...
}

But beware your are still in a ISR and all Interrupts are OFF and you are blocking EVERYTHING. One should not lollygag nor dilly dally, here. Do you something quick and get out.

Interrupting with SoftwareSerial on Arduino

1 Answers