void ibm4704_init(void)
{
- // POR
- //_delay_ms(2500);
- //while ( 0xA3 != ibm4704_recv() ) ;
-
inhibit();
- DDRD |= 1<<3;
- PORTD &= ~(1<<3);
}
+/*
+Host to Keyboard
+----------------
+Data bits are LSB first and Parity is odd. Clock has around 60us high and 30us low part.
+
+ ____ __ __ __ __ __ __ __ __ __ ________
+Clock \______/ \_/ \_/ \_/ \_/ \_/ \_/ \_/ \_/ \_/
+ ^ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ___
+Data ____|__/ X____X____X____X____X____X____X____X____X____X \___
+ | Start 0 1 2 3 4 5 6 7 P Stop
+ Request by host
+
+Start bit: can be long as 300-350us.
+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.
+ Host writes a bit while Clock is hi and Keyboard reads while low.
+Stop bit: Host releases or pulls up Data line to hi after 9th clock and waits for keyboard pull down the line to lo.
+*/
uint8_t ibm4704_send(uint8_t data)
{
bool parity = true; // odd parity
/* Request to send */
idle();
clock_lo();
-PIND |= 1<<3;
/* wait for Start bit(Clock:lo/Data:hi) */
WAIT(data_hi, 300, 0x30);
/* Data bit */
for (uint8_t i = 0; i < 8; i++) {
- WAIT(clock_hi, 100, 0x31);
+ WAIT(clock_hi, 100, 0x40+i);
//_delay_us(5);
-PIND |= 1<<3;
if (data&(1<<i)) {
parity = !parity;
data_hi();
} else {
data_lo();
}
- WAIT(clock_lo, 100, 0x32);
+ WAIT(clock_lo, 100, 0x48+i);
}
/* Parity bit */
- WAIT(clock_hi, 100, 4);
-PIND |= 1<<3;
+ WAIT(clock_hi, 100, 0x34);
if (parity) { data_hi(); } else { data_lo(); }
- WAIT(clock_lo, 100, 5);
+ WAIT(clock_lo, 100, 0x35);
/* Stop bit */
- WAIT(clock_hi, 100, 4);
+ WAIT(clock_hi, 100, 0x34);
data_hi();
/* End */
- WAIT(data_lo, 100, 6);
+ WAIT(data_lo, 100, 0x36);
inhibit();
_delay_us(200); // wait to recover clock to hi
return 0;
ERROR:
inhibit();
-xprintf("x%02X ", ibm4704_error);
+ if (ibm4704_error >= 0x30) {
+ xprintf("x%02X ", ibm4704_error);
+ }
_delay_us(200); // wait to recover clock to hi
return -1;
}
}
/*
-Keyboard to Host:
-Clock ~~~~___~~_~~_~~_~~_~~_~~_~~_~~_~~_~~~~~~~~ H:60us/L:30us
-
-Data ____~~X==X==X==X==X==X==X==X==X==X________
- | 0 1 2 3 4 5 6 7 P(odd)
- | LSB MSB
- Start bit(80us)
+Keyboard to Host
+----------------
+Data bits are LSB first and Parity is odd. Clock has around 60us high and 30us low part.
+
+ ____ __ __ __ __ __ __ __ __ __ ________
+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.
+Stop bit: Keyboard pulls down Data line to lo after 9th clock.
*/
uint8_t ibm4704_recv(void)
{
_delay_us(5); // wait for line settles
/* start bit */
- WAIT(clock_lo, 100, 1); // wait for keyboard to send
- WAIT(data_hi, 100, 2); // can be delayed that long
+ WAIT(clock_lo, 100, 0x11); // wait for keyboard to send
+ WAIT(data_hi, 100, 0x12); // can be delayed that long
- WAIT(clock_hi, 100, 3); // first rising edge which can take longer
+ WAIT(clock_hi, 100, 0x13); // first rising edge which can take longer
/* data */
for (uint8_t i = 0; i < 8; i++) {
WAIT(clock_hi, 100, 0x20+i);
}
/* parity */
- WAIT(clock_hi, 100, 7);
+ WAIT(clock_hi, 100, 0x17);
if (data_in() != parity) {
ibm4704_error = IBM4704_ERR_PARITY;
goto ERROR;
}
- WAIT(clock_lo, 150, 8);
+ WAIT(clock_lo, 150, 0x18);
/* stop bit */
- WAIT(clock_hi, 100, 9);
- WAIT(data_lo, 1, 9);
+ WAIT(clock_hi, 100, 0x19);
+ WAIT(data_lo, 1, 0x19);
inhibit();
_delay_us(200); // wait to recover clock to hi
return data;
ERROR:
- if (ibm4704_error > 2) {
+ if (ibm4704_error > 0x12) {
xprintf("x%02X ", ibm4704_error);
}
inhibit();