void ibm4704_init(void)
{
+ inhibit(); // keep keyboard from sending
IBM4704_INT_INIT();
IBM4704_INT_ON();
- idle();
+ idle(); // allow keyboard sending
}
/*
| Start 0 1 2 3 4 5 6 7 P Stop
Request by host
-Start bit: can be long as 300-350us.
+Start bit: can be long as 300-350us during start up and upto 2500us while key scanning
Request: Host pulls Clock line down to request to send a command.
Timing: After Request keyboard pull up Data and down Clock line to low for start bit.
After request host release Clock line once Data line becomes hi.
clock_lo();
/* wait for Start bit(Clock:lo/Data:hi) */
- WAIT(data_hi, 300, 0x30);
+ WAIT(data_hi, 5000, 0x30);
/* Data bit */
for (uint8_t i = 0; i < 8; i++) {
return 0;
ERROR:
idle();
- if (ibm4704_error > 0x30) {
+ if (ibm4704_error >= 0x30) {
xprintf("S:%02X ", ibm4704_error);
}
IBM4704_INT_ON();
return rbuf_dequeue();
}
+uint8_t ibm4704_recv(void)
+{
+ if (rbuf_has_data()) {
+ return rbuf_dequeue();
+ } else {
+ return -1;
+ }
+}
+
/*
Keyboard to Host
----------------
Data bits are LSB first and Parity is odd. Clock has around 60us high and 30us low part.
- ____ __ __ __ __ __ __ __ __ __ ________
-Clock \____/ \_/ \_/ \_/ \_/ \_/ \_/ \_/ \_/ \_/
+ ____ __ __ __ __ __ __ __ __ __ _______
+Clock \_____/ \_/ \_/ \_/ \_/ \_/ \_/ \_/ \_/ \_/
____ ____ ____ ____ ____ ____ ____ ____ ____ ____
Data ____/ X____X____X____X____X____X____X____X____X____X________
Start 0 1 2 3 4 5 6 7 P Stop
Start bit: can be long as 300-350us.
Inhibit: Pull Data line down to inhibit keyboard to send.
-Timing: Host reads bit while Clock is hi.
+Timing: Host reads bit while Clock is hi.(rising edge)
Stop bit: Keyboard pulls down Data line to lo after 9th clock.
*/
-uint8_t ibm4704_recv(void)
-{
- if (rbuf_has_data()) {
- return rbuf_dequeue();
- } else {
- return -1;
- }
-}
-
ISR(IBM4704_INT_VECT)
{
static enum {
- INIT, START, BIT0, BIT1, BIT2, BIT3, BIT4, BIT5, BIT6, BIT7, PARITY,
- } state = INIT;
+ BIT0, BIT1, BIT2, BIT3, BIT4, BIT5, BIT6, BIT7, PARITY, STOP
+ } state = BIT0;
// LSB first
static uint8_t data = 0;
// Odd parity
static uint8_t parity = false;
ibm4704_error = 0;
- // return unless falling edge
- if (clock_in()) { goto RETURN; } // why this occurs?
- state++;
switch (state) {
- case START:
- // Data:Low
- WAIT(data_hi, 10, state);
- break;
case BIT0:
case BIT1:
case BIT2:
}
if (!parity)
goto ERROR;
+ break;
+ case STOP:
+ // Data:Low
+ WAIT(data_lo, 100, state);
rbuf_enqueue(data);
ibm4704_error = IBM4704_ERR_NONE;
goto DONE;
default:
goto ERROR;
}
+ state++;
goto RETURN;
ERROR:
ibm4704_error = state;
while (ibm4704_send(0xFE)) _delay_ms(1); // resend
xprintf("R:%02X%02X\n", state, data);
DONE:
- state = INIT;
+ state = BIT0;
data = 0;
parity = false;
RETURN: