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- /*
- Copyright 2010,2011,2012,2013 Jun WAKO <[email protected]>
- */
- #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();
- }
-
- /*
- 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
- 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++) {
- WAIT(clock_hi, 100, 0x40+i);
- //_delay_us(5);
- if (data&(1<<i)) {
- parity = !parity;
- data_hi();
- } else {
- data_lo();
- }
- WAIT(clock_lo, 100, 0x48+i);
- }
-
- /* Parity bit */
- WAIT(clock_hi, 100, 0x34);
- if (parity) { data_hi(); } else { data_lo(); }
- WAIT(clock_lo, 100, 0x35);
-
- /* Stop bit */
- WAIT(clock_hi, 100, 0x34);
- data_hi();
-
- /* End */
- WAIT(data_lo, 100, 0x36);
-
- inhibit();
- _delay_us(200); // wait to recover clock to hi
- return 0;
- ERROR:
- inhibit();
- if (ibm4704_error >= 0x30) {
- xprintf("x%02X ", ibm4704_error);
- }
- _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
- ----------------
- 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)
- {
- uint8_t data = 0;
- bool parity = true; // odd parity
- ibm4704_error = IBM4704_ERR_NONE;
-
- idle();
- _delay_us(5); // wait for line settles
-
- /* start bit */
- WAIT(clock_lo, 100, 0x11); // wait for keyboard to send
- WAIT(data_hi, 100, 0x12); // can be delayed that long
-
- 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);
- //_delay_us(5);
- if (data_in()) {
- parity = !parity;
- data |= (1<<i);
- }
- WAIT(clock_lo, 150, 0x28+i);
- }
-
- /* parity */
- WAIT(clock_hi, 100, 0x17);
- if (data_in() != parity) {
- ibm4704_error = IBM4704_ERR_PARITY;
- goto ERROR;
- }
- WAIT(clock_lo, 150, 0x18);
-
- /* stop bit */
- 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 > 0x12) {
- xprintf("x%02X ", ibm4704_error);
- }
- inhibit();
- _delay_us(200); // wait to recover clock to hi
- return -1;
- }
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