File content as of revision 12:cd58d03b8559:

// Modified by K.Arai / JH1PJL     May 10th, 2020

#include "SoftSerial.h"

// please make a constructor in main.cpp if you use below pc & led
#if DEBUG_TIMING == 2
    extern Serial pc;
    extern DigitalOut test_point;
#   define TP_ON   {test_point = 1;}
#   define TP_OFF  {test_point = 0;}
#   define DBG_PRINTF(...) pc.printf(__VA_ARGS__)
#else
#   define TP_ON   {;}
#   define TP_OFF  {;}
#   define DBG_PRINTF(...) {;}
#endif

//  Random estimation of the overhead of mbed libs,
//      makes slow devices like LPC812 @ 12MHz perform better
uint32_t overhead_us = 200 * 1000000 / SystemCoreClock;

int SoftSerial::_getc( void )
{
    while(!readable()) {
        YIELD;
    }
    out_valid = false;
    return out_buffer;
}

int SoftSerial::readable(void)
{
    return out_valid;
}

//Start receiving byte
void SoftSerial::rx_gpio_irq_handler(void)
{
    TP_ON;
    rxticker.prime(0);
    rx->fall(NULL);
    rx_bit = 0;
    rx_error = false;
    // dummy setting for 1st timer interrupt
    rx_1st = true;
    rxticker.setNext(0);
    rx_st_time = us_ticker_read();
    TP_OFF;
};

void SoftSerial::rx_handler(void)
{
    TP_ON;
    // dummy IRQ for 1st shot
    if (rx_1st) {
        rx_1st = false;
        //rxticker.setNext(bit_period + (bit_period >> 1) - overhead_us);
        int next_preiod = us_ticker_read() - rx_st_time;
        next_preiod = bit_period + (bit_period >> 1) - next_preiod;
        if (next_preiod > 0) {
            rxticker.setNext(next_preiod);
        } else {
            rxticker.setNext(0);
        }
        TP_OFF;
        return;
    }
    //Receive data
    int val = rx->read();

    rxticker.setNext(bit_period);
    rx_bit++;


    if (rx_bit <= _bits) {
        read_buffer |= val << (rx_bit - 1);
        TP_OFF;
        return;
    }

    //Receive parity
    bool parity_count;
    if (rx_bit == _bits + 1) {
        switch (_parity) {
            case Forced1:
                if (val == 0)
                    rx_error = true;
                return;
            case Forced0:
                if (val == 1)
                    rx_error = true;
                return;
            case Even:
            case Odd:
                parity_count = val;
                for (int i = 0; i<_bits; i++) {
                    if (((read_buffer >> i) & 0x01) == 1)
                        parity_count = !parity_count;
                }
                if ((parity_count) && (_parity == Even))
                    rx_error = true;
                if ((!parity_count) && (_parity == Odd))
                    rx_error = true;
                return;
            case None:
            default:
                ;
        }
    }

    //Receive stop
    if (rx_bit < _bits + (bool)_parity + _stop_bits) {
        if (!val)
            rx_error = true;
        TP_OFF;
        return;
    }

    //The last stop bit
    if (!val)
        rx_error = true;

    if (!rx_error) {
        out_valid = true;
        out_buffer = read_buffer;
        fpointer[RxIrq].call();
    }
    read_buffer = 0;
    rxticker.detach();
    //rx->fall(this, &SoftSerial::rx_gpio_irq_handler);
    rx->fall(callback(this, &SoftSerial::rx_gpio_irq_handler));
    TP_OFF;
}