// TODO: send using interrupt if available
uint8_t ps2_host_send(uint8_t data)
{
uint8_t res = 0;
bool parity = true;
ps2_error = PS2_ERR_NONE;
#ifdef PS2_USE_INT
PS2_INT_OFF();
#endif
/* terminate a transmission if we have */
inhibit();
_delay_us(200); // at least 100us
/* start bit [1] */
data_lo();
clock_hi();
WAIT(clock_lo, 20000, 10); // may take 15ms at most until device starts clocking
/* data [2-9] */
for (uint8_t i = 0; i < 8; i++) {
_delay_us(15);
if (data&(1<<i)) {
parity = !parity;
data_hi();
} else {
data_lo();
}
WAIT(clock_hi, 50, 2);
WAIT(clock_lo, 50, 3);
}
/* parity [10] */
_delay_us(15);
if (parity) { data_hi(); } else { data_lo(); }
WAIT(clock_hi, 50, 4);
WAIT(clock_lo, 50, 5);
/* stop bit [11] */
_delay_us(15);
data_hi();
/* ack [12] */
WAIT(data_lo, 50, 6);
WAIT(clock_lo, 50, 7);
/* wait for idle state */
WAIT(clock_hi, 50, 8);
WAIT(data_hi, 50, 9);
#ifdef PS2_USE_INT
PS2_INT_ON();
#endif
res = ps2_host_recv_response();
ERROR:
#ifdef PS2_USE_INT
PS2_INT_ON();
idle();
#else
inhibit();
#endif
return res;
}
uint8_t ps2_host_send(uint8_t data)
{
bool parity = true;
ps2_error = PS2_ERR_NONE;
PS2_INT_OFF();
/* terminate a transmission if we have */
inhibit();
_delay_us(100); // 100us [4]p.13, [5]p.50
/* 'Request to Send' and Start bit */
data_lo();
clock_hi();
WAIT(clock_lo, 10000, 10); // 10ms [5]p.50
/* Data bit[2-9] */
for (uint8_t i = 0; i < 8; i++) {
_delay_us(15);
if (data&(1<<i)) {
parity = !parity;
data_hi();
} else {
data_lo();
}
WAIT(clock_hi, 50, 2);
WAIT(clock_lo, 50, 3);
}
/* Parity bit */
_delay_us(15);
if (parity) { data_hi(); } else { data_lo(); }
WAIT(clock_hi, 50, 4);
WAIT(clock_lo, 50, 5);
/* Stop bit */
_delay_us(15);
data_hi();
/* Ack */
WAIT(data_lo, 50, 6);
WAIT(clock_lo, 50, 7);
/* wait for idle state */
WAIT(clock_hi, 50, 8);
WAIT(data_hi, 50, 9);
idle();
PS2_INT_ON();
return ps2_host_recv_response();
ERROR:
idle();
PS2_INT_ON();
return 0;
}
/* receive data when host want else inhibit communication */
uint8_t ps2_host_recv_response(void)
{
uint8_t data = 0;
#ifdef PS2_USE_INT
PS2_INT_OFF();
#endif
/* terminate a transmission if we have */
inhibit();
_delay_us(100);
/* release lines(idle state) */
idle();
/* wait start bit */
wait_clock_lo(25000); // command response may take 20 ms at most
data = recv_data();
inhibit();
return data;
}