r65emu/ps2drv.cpp

#include <Arduino.h>
#include "ps2drv.h"

#define BUFFER_SIZE 16
static volatile uint8_t buffer[BUFFER_SIZE];
static volatile uint8_t head, tail;
static uint8_t DataPin;

// The ISR for the external interrupt
void ps2interrupt(void)
{
	static uint8_t bitcount=0;
	static uint8_t incoming=0;
	static uint32_t prev_ms=0;
	uint32_t now_ms;
	uint8_t n, val;

	val = digitalRead(DataPin);
	now_ms = millis();
	if (now_ms - prev_ms > 250) {
		bitcount = 0;
		incoming = 0;
	}
	prev_ms = now_ms;
	n = bitcount - 1;
	if (n <= 7) {
		incoming |= (val << n);
	}
	bitcount++;
	if (bitcount == 11) {
		uint8_t i = head + 1;		
		if (i == BUFFER_SIZE) i = 0;
		if (i != tail) {
			buffer[i] = incoming;
			head = i;
		}
		bitcount = 0;
		incoming = 0;
	}
}

bool PS2Driver::available() {
	if (head == tail)
		return false;

	uint8_t i = tail+1;
	if (i == BUFFER_SIZE) i = 0;
	if (buffer[i] == 0xf0)
		return i != head;
	return true;
}

unsigned PS2Driver::read2() {
	if (head == tail)
		return 0;

	uint8_t i = tail+1;
	if (i == BUFFER_SIZE) i = 0;
	tail = i;
	if (buffer[i] != 0xf0)
		return buffer[i];
	return 0xf000 | read2();
}

unsigned PS2Driver::peek() {
	if (head == tail)
		return 0;

	uint8_t i = tail+1;
	if (i == BUFFER_SIZE) i = 0;
	if (buffer[i] == 0xf0) {
		if (++i == BUFFER_SIZE) i = 0;
		return 0xf000 | buffer[i];
	}
	return buffer[i];
}

void PS2Driver::begin(uint8_t data_pin, uint8_t irq_pin)
{
	DataPin = data_pin;
	pinMode(irq_pin, INPUT_PULLUP);
	pinMode(data_pin, INPUT_PULLUP);
	attachInterrupt(irq_pin, ps2interrupt, FALLING);
	head = tail = 0;
}