estimate clocks modified SoftwareSerial.cpp calc code

#include <stdio.h>
#include <stdint.h>

static uint16_t subtract_cap(uint16_t num, uint16_t sub) {
	if (num > sub)
		return num - sub;
	else
		return 1;
}

void calc(int f_cpu, int speed, uint16_t *txd, uint16_t *rxd_cent, uint16_t *rxd_intra, uint16_t *rxd_stop)
{
#define BASE	4

	uint16_t bit_delay = (f_cpu / speed) / BASE;

	*txd = subtract_cap(bit_delay, 14 / BASE);
	*rxd_cent = subtract_cap(bit_delay / 2, (4 + 4 + 44 + 14 - 14) / BASE);
	*rxd_intra = subtract_cap(bit_delay, 14 / BASE);
	*rxd_stop = subtract_cap(bit_delay * 3 / 4, (28 + 6) / BASE);

	/* convert to delay times -> real clocks */
	*txd *= BASE;
	*rxd_cent *= BASE;
	*rxd_intra *= BASE;
	*rxd_stop *= BASE;
}

/* original calculation code */
void calc2(int f_cpu, int speed, uint16_t *txd, uint16_t *rxd_cent, uint16_t *rxd_intra, uint16_t *rxd_stop)
{
	uint16_t bit_delay = (f_cpu / speed) / 4;

	*txd = subtract_cap(bit_delay, 15 / 4);
	*rxd_cent = subtract_cap(bit_delay / 2, (4 + 4 + 75 + 17 - 23) / 4);
	*rxd_intra = subtract_cap(bit_delay, 23 / 4);
	*rxd_stop = subtract_cap(bit_delay * 3 / 4, (37 + 11) / 4);

	/* convert to delay times -> real clocks */
	*txd *= 4;
	*rxd_cent *= 4;
	*rxd_intra *= 4;
	*rxd_stop *= 4;
}

int main(int argc, char *argv[])
{
#define F_CPU	16000000

	int speed_table[] = {
		300, 600, 1200, 2400, 4800, 9600, 19200,
		38400, 57600, 115200, 230400,
	};
	int i;
	uint16_t _rx_delay_centering, _rx_delay_centering2;
	uint16_t _rx_delay_intrabit, _rx_delay_intrabit2;
	uint16_t _rx_delay_stopbit, _rx_delay_stopbit2;
	uint16_t _tx_delay, _tx_delay2;

	for (i = 0; i < sizeof(speed_table) / sizeof(int); i++) {
		calc(F_CPU, speed_table[i], &_tx_delay, &_rx_delay_centering,
		     &_rx_delay_intrabit, &_rx_delay_stopbit);
		calc2(F_CPU, speed_table[i], &_tx_delay2, &_rx_delay_centering2,
		     &_rx_delay_intrabit2, &_rx_delay_stopbit2);


		printf("%8d %6d %5d(%d) %5d(%d) %5d(%d) %5d(%d)\n",
		       F_CPU, speed_table[i],
		       _tx_delay, _tx_delay - _tx_delay2,
		       _rx_delay_centering, _rx_delay_centering - _rx_delay_centering2,
		       _rx_delay_intrabit, _rx_delay_intrabit - _rx_delay_intrabit2,
		       _rx_delay_stopbit, _rx_delay_stopbit - _rx_delay_stopbit2);
	}

	return 0;
}