2 Copyright 2010,2011,2012,2013,2019 Jun WAKO <wakojun@gmail.com>
4 This software is licensed with a Modified BSD License.
5 All of this is supposed to be Free Software, Open Source, DFSG-free,
6 GPL-compatible, and OK to use in both free and proprietary applications.
7 Additions and corrections to this file are welcome.
10 Redistribution and use in source and binary forms, with or without
11 modification, are permitted provided that the following conditions are met:
13 * Redistributions of source code must retain the above copyright
14 notice, this list of conditions and the following disclaimer.
16 * Redistributions in binary form must reproduce the above copyright
17 notice, this list of conditions and the following disclaimer in
18 the documentation and/or other materials provided with the
21 * Neither the name of the copyright holders nor the names of
22 contributors may be used to endorse or promote products derived
23 from this software without specific prior written permission.
25 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
26 AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
27 IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
28 ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
29 LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
30 CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
31 SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
32 INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
33 CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
34 ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
35 POSSIBILITY OF SUCH DAMAGE.
39 * IBM PC keyboard protocol
43 #include <avr/interrupt.h>
44 #include <util/atomic.h>
51 #define WAIT(stat, us, err) do { \
52 if (!wait_##stat(us)) { \
59 volatile uint8_t ibmpc_protocol = IBMPC_PROTOCOL_AT;
60 volatile uint8_t ibmpc_error = IBMPC_ERR_NONE;
62 /* 2-byte buffer for data received from keyhboard
66 * sstt: two data(full)
67 * 0xFF can not be stored as data in buffer because it means empty or no data.
69 static volatile uint16_t recv_data = 0xFFFF;
70 /* internal state of receiving data */
71 static volatile uint16_t isr_state = 0x8000;
72 static uint8_t timer_start = 0;
74 void ibmpc_host_init(void)
76 // initialize reset pin to HiZ
83 void ibmpc_host_enable(void)
89 void ibmpc_host_disable(void)
95 int16_t ibmpc_host_send(uint8_t data)
98 ibmpc_error = IBMPC_ERR_NONE;
100 if (ibmpc_protocol == IBMPC_PROTOCOL_XT) return -1;
102 dprintf("w%02X ", data);
106 /* terminate a transmission if we have */
108 wait_us(100); // 100us [4]p.13, [5]p.50
110 /* 'Request to Send' and Start bit */
113 WAIT(clock_lo, 10000, 1); // 10ms [5]p.50
116 for (uint8_t i = 0; i < 8; i++) {
124 WAIT(clock_hi, 50, 2);
125 WAIT(clock_lo, 50, 3);
130 if (parity) { data_hi(); } else { data_lo(); }
131 WAIT(clock_hi, 50, 4);
132 WAIT(clock_lo, 50, 5);
139 WAIT(data_lo, 50, 6);
140 WAIT(clock_lo, 50, 7);
142 /* wait for idle state */
143 WAIT(clock_hi, 50, 8);
144 WAIT(data_hi, 50, 9);
146 // clear buffer to get response correctly
148 ibmpc_host_isr_clear();
152 return ibmpc_host_recv_response();
154 ibmpc_error |= IBMPC_ERR_SEND;
161 * Receive data from keyboard
163 int16_t ibmpc_host_recv(void)
168 ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
170 if ((data&0xFF00) != 0xFF00) { // recv_data:sstt -> recv_data:FFtt, ret:ss
171 ret = (data>>8)&0x00FF;
172 recv_data = data | 0xFF00;
173 } else if (data != 0xFFFF) { // recv_data:FFss -> recv_data:FFFF, ret:ss
175 recv_data = data | 0x00FF;
179 if (ret != 0xFF) dprintf("r%02X ", ret);
180 if (recv_data != 0xFFFF) dprintf("b%04X ", recv_data);
181 return ((ret != 0xFF) ? ret : -1);
185 int16_t ibmpc_host_recv_response(void)
187 // Command may take 25ms/20ms at most([5]p.46, [3]p.21)
190 while (retry-- && (data = ibmpc_host_recv()) == -1) {
196 void ibmpc_host_isr_clear(void)
202 // NOTE: With this ISR data line can be read within 2us after clock falling edge.
203 // To read data line early as possible:
204 // write naked ISR with asembly code to read the line and call C func to do other job?
208 dbit = IBMPC_DATA_PIN&(1<<IBMPC_DATA_BIT);
212 // use only the least byte of millisecond timer
213 asm("lds %0, %1" : "=r" (t) : "p" (&timer_count));
214 //t = (uint8_t)timer_count; // compiler uses four registers instead of one
215 if (isr_state == 0x8000) {
218 // should not take more than 1ms
219 if (timer_start != t && (uint8_t)(timer_start + 1) != t) {
220 ibmpc_error = IBMPC_ERR_TIMEOUT;
222 // timeout error recovery by clearing isr_state?
228 isr_state = isr_state>>1;
229 if (dbit) isr_state |= 0x8000;
231 // isr_state: state of receiving data from keyboard
233 // This should be initialized with 0x8000 before receiving data and
234 // the MSB '*1' works as marker to discrimitate between protocols.
235 // It stores sampled bit at MSB after right shift on each clock falling edge.
237 // XT protocol has two variants of signaling; XT_IBM and XT_Clone.
238 // XT_IBM uses two start bits 0 and 1 while XT_Clone uses just start bit 1.
239 // https://github.com/tmk/tmk_keyboard/wiki/IBM-PC-XT-Keyboard-Protocol
241 // 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
242 // -----------------------------------------------------
243 // *1 0 0 0 0 0 0 0 | 0 0 0 0 0 0 0 0 Initial state(0x8000)
245 // x x x x x x x x | 0 0 0 0 0 0 0 0 midway(0-7 bits received)
246 // x x x x x x x x | *1 0 0 0 0 0 0 0 midway(8 bits received)
247 // b6 b5 b4 b3 b2 b1 b0 1 | 0 *1 0 0 0 0 0 0 XT_IBM-midway ^1
248 // b7 b6 b5 b4 b3 b2 b1 b0 | 0 *1 0 0 0 0 0 0 AT-midway ^1
249 // b7 b6 b5 b4 b3 b2 b1 b0 | 1 *1 0 0 0 0 0 0 XT_Clone-done
250 // pr b7 b6 b5 b4 b3 b2 b1 | 0 0 *1 0 0 0 0 0 AT-midway[b0=0]
251 // b7 b6 b5 b4 b3 b2 b1 b0 | 1 0 *1 0 0 0 0 0 XT_IBM-done ^2
252 // pr b7 b6 b5 b4 b3 b2 b1 | 1 0 *1 0 0 0 0 0 AT-midway[b0=1] ^2
253 // x x x x x x x x | x 1 1 0 0 0 0 0 illegal
254 // st pr b7 b6 b5 b4 b3 b2 | b1 b0 0 *1 0 0 0 0 AT-done
255 // x x x x x x x x | x x 1 *1 0 0 0 0 illegal
256 // all other states than above illegal
258 // ^1: AT and XT_IBM takes same state.
259 // ^2: AT and XT_IBM takes same state in case that AT b0 is 1,
260 // we have to check AT stop bit to discriminate between the two protocol.
261 switch (isr_state & 0xFF) {
264 case 0b01000000: // ^1
271 isr_state = isr_state>>8;
274 case 0b10100000: // ^2
277 // wait for rising and falling edge of AT stop bit to discriminate between XT and AT
278 while (!(IBMPC_CLOCK_PIN&(1<<IBMPC_CLOCK_BIT)) && us) { wait_us(1); us--; }
279 while ( IBMPC_CLOCK_PIN&(1<<IBMPC_CLOCK_BIT) && us) { wait_us(1); us--; }
282 // found stop bit: AT-midway - process the stop bit in next ISR
285 // no stop bit: XT_IBM-done
286 isr_state = isr_state>>8;
296 // TODO: parity check?
297 isr_state = isr_state>>6;
306 default: // xxxx_oooo(any 1 in low nibble)
308 ibmpc_error = IBMPC_ERR_ILLEGAL;
315 recv_data = 0xFF00; // clear data and scancode of error 0x00
318 if ((isr_state & 0x00FF) == 0x00FF) {
319 // receive error code 0xFF
320 ibmpc_error = IBMPC_ERR_FF;
322 if ((recv_data & 0xFF00) != 0xFF00) {
323 // buffer full and overwritten
324 ibmpc_error = IBMPC_ERR_FULL;
326 recv_data = recv_data<<8;
327 recv_data |= isr_state & 0xFF;
328 isr_state = 0x8000; // clear to next data
333 /* send LED state to keyboard */
334 void ibmpc_host_set_led(uint8_t led)
336 ibmpc_host_send(0xED);
337 ibmpc_host_send(led);