/*
-Copyright 2010,2011,2012,2013 Jun WAKO <wakojun@gmail.com>
+Copyright 2018 Jun WAKO <wakojun@gmail.com>
+Copyright 2016 Ethan Apodaca <papodaca@gmail.com>
This software is licensed with a Modified BSD License.
All of this is supposed to be Free Software, Open Source, DFSG-free,
POSSIBILITY OF SUCH DAMAGE.
*/
-/*
- * PS/2 protocol Pin interrupt version
- */
-
#include <stdbool.h>
#include <avr/interrupt.h>
#include <util/delay.h>
#include "pbuff.h"
#include "xt.h"
-#include "xt_io.h"
#include "wait.h"
#include "print.h"
void xt_host_init(void)
{
XT_INT_INIT();
+ XT_INT_OFF();
+
+ /* hard reset */
+#ifdef XT_RESET
+ XT_RESET();
+#endif
+
+ /* soft reset: pull clock line down for 20ms */
+ XT_DATA_LO();
+ XT_CLOCK_LO();
+ _delay_ms(20);
+
+ /* input mode with pullup */
+ XT_CLOCK_IN();
+ XT_DATA_IN();
+
XT_INT_ON();
}
ISR(XT_INT_VECT)
{
- static uint8_t state = 0;
+ /*
+ * XT signal format consits of 10 or 9 clocks and sends start bits and 8-bit data,
+ * which should be read on falling edge of clock.
+ *
+ * start(0), start(1), bit0, bit1, bit2, bit3, bit4, bit5, bit6, bit7
+ *
+ * Original IBM XT keyboard sends start(0) bit while some of clones don't.
+ * Start(0) bit is read as low on data line while start(1) as high.
+ *
+ * https://github.com/tmk/tmk_keyboard/wiki/IBM-PC-XT-Keyboard-Protocol
+ */
+ static enum {
+ START, BIT0, BIT1, BIT2, BIT3, BIT4, BIT5, BIT6, BIT7
+ } state = START;
static uint8_t data = 0;
- if (state == 0) {
- if (data_in())
- state++;
- } else if (state >= 1 && state <= 8) {
- wait_clock_lo(20);
- data >>= 1;
- if (data_in())
- data |= 0x80;
- if (state == 8)
- goto END;
- state++;
- } else {
- goto DONE;
+ uint8_t dbit = XT_DATA_READ();
+
+ // This is needed if using PCINT which can be called on both falling and rising edge
+ //if (XT_CLOCK_READ()) return;
+
+ switch (state) {
+ case START:
+ // ignore start(0) bit
+ if (!dbit) return;
+ break;
+ case BIT0 ... BIT7:
+ data >>= 1;
+ if (dbit)
+ data |= 0x80;
+ break;
+ }
+ if (state++ == BIT7) {
+ pbuf_enqueue(data);
+ state = START;
+ data = 0;
}
- goto RETURN;
-END:
- pbuf_enqueue(data);
-DONE:
- state = 0;
- data = 0;
-RETURN:
return;
}