qmk_firmware/protocol/ibm4704.c

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/*
Copyright 2010,2011,2012,2013 Jun WAKO <wakojun@gmail.com>
*/
#include <stdbool.h>
#include <util/delay.h>
#include "debug.h"
#include "ibm4704.h"
#define WAIT(stat, us, err) do { \
if (!wait_##stat(us)) { \
ibm4704_error = err; \
goto ERROR; \
} \
} while (0)
uint8_t ibm4704_error = 0;
void ibm4704_init(void)
{
inhibit();
}
uint8_t ibm4704_send(uint8_t data)
{
bool parity = true; // odd parity
ibm4704_error = 0;
/* Request to send */
idle();
clock_lo();
/* wait for Start bit(Clock:lo/Data:hi) */
WAIT(data_hi, 300, 0x30);
/* Data bit */
for (uint8_t i = 0; i < 8; i++) {
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WAIT(clock_hi, 100, 0x40+i);
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//_delay_us(5);
if (data&(1<<i)) {
parity = !parity;
data_hi();
} else {
data_lo();
}
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WAIT(clock_lo, 100, 0x48+i);
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}
/* Parity bit */
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WAIT(clock_hi, 100, 0x34);
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if (parity) { data_hi(); } else { data_lo(); }
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WAIT(clock_lo, 100, 0x35);
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/* Stop bit */
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WAIT(clock_hi, 100, 0x34);
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data_hi();
/* End */
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WAIT(data_lo, 100, 0x36);
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inhibit();
_delay_us(200); // wait to recover clock to hi
return 0;
ERROR:
inhibit();
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if (ibm4704_error >= 0x30) {
xprintf("x%02X ", ibm4704_error);
}
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_delay_us(200); // wait to recover clock to hi
return -1;
}
/* receive data when host want else inhibit communication */
uint8_t ibm4704_recv_response(void)
{
// 250 * 100us(wait start bit in ibm4704_recv)
uint8_t data = 0;
uint8_t try = 250;
do {
data = ibm4704_recv();
} while (try-- && ibm4704_error);
return data;
}
/*
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)
*/
uint8_t ibm4704_recv(void)
{
uint8_t data = 0;
bool parity = true; // odd parity
ibm4704_error = IBM4704_ERR_NONE;
idle();
_delay_us(5); // wait for line settles
/* start bit */
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WAIT(clock_lo, 100, 0x11); // wait for keyboard to send
WAIT(data_hi, 100, 0x12); // can be delayed that long
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WAIT(clock_hi, 100, 0x13); // first rising edge which can take longer
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/* data */
for (uint8_t i = 0; i < 8; i++) {
WAIT(clock_hi, 100, 0x20+i);
//_delay_us(5);
if (data_in()) {
parity = !parity;
data |= (1<<i);
}
WAIT(clock_lo, 150, 0x28+i);
}
/* parity */
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WAIT(clock_hi, 100, 0x17);
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if (data_in() != parity) {
ibm4704_error = IBM4704_ERR_PARITY;
goto ERROR;
}
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WAIT(clock_lo, 150, 0x18);
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/* stop bit */
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WAIT(clock_hi, 100, 0x19);
WAIT(data_lo, 1, 0x19);
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inhibit();
_delay_us(200); // wait to recover clock to hi
return data;
ERROR:
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if (ibm4704_error > 0x12) {
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xprintf("x%02X ", ibm4704_error);
}
inhibit();
_delay_us(200); // wait to recover clock to hi
return -1;
}