xref: /btstack/src/hci_transport_h5.c (revision ab2c6ae4b737d5e801d3defe4117331eb244ebb7)
1 /*
2  * Copyright (C) 2016 BlueKitchen GmbH
3  *
4  * Redistribution and use in source and binary forms, with or without
5  * modification, are permitted provided that the following conditions
6  * are met:
7  *
8  * 1. Redistributions of source code must retain the above copyright
9  *    notice, this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright
11  *    notice, this list of conditions and the following disclaimer in the
12  *    documentation and/or other materials provided with the distribution.
13  * 3. Neither the name of the copyright holders nor the names of
14  *    contributors may be used to endorse or promote products derived
15  *    from this software without specific prior written permission.
16  * 4. Any redistribution, use, or modification is done solely for
17  *    personal benefit and not for any commercial purpose or for
18  *    monetary gain.
19  *
20  * THIS SOFTWARE IS PROVIDED BY BLUEKITCHEN GMBH AND CONTRIBUTORS
21  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
22  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
23  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL MATTHIAS
24  * RINGWALD OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
25  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
26  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
27  * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
28  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
29  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
30  * THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31  * SUCH DAMAGE.
32  *
33  * Please inquire about commercial licensing options at
34  * [email protected]
35  *
36  */
37 
38 #define __BTSTACK_FILE__ "hci_transport_h5.c"
39 
40 /*
41  *  hci_transport_h5.c
42  *
43  *  HCI Transport API implementation for basic H5 protocol
44  *
45  *  Created by Matthias Ringwald on 4/29/09.
46  */
47 
48 #include "hci.h"
49 #include "btstack_slip.h"
50 #include "btstack_debug.h"
51 #include "hci_transport.h"
52 #include "btstack_uart_block.h"
53 
54 typedef enum {
55     LINK_UNINITIALIZED,
56     LINK_INITIALIZED,
57     LINK_ACTIVE
58 } hci_transport_link_state_t;
59 
60 typedef enum {
61     HCI_TRANSPORT_LINK_SEND_SYNC            = 1 << 0,
62     HCI_TRANSPORT_LINK_SEND_SYNC_RESPONSE   = 1 << 1,
63     HCI_TRANSPORT_LINK_SEND_CONFIG          = 1 << 2,
64     HCI_TRANSPORT_LINK_SEND_CONFIG_RESPONSE = 1 << 3,
65     HCI_TRANSPORT_LINK_SEND_SLEEP           = 1 << 4,
66     HCI_TRANSPORT_LINK_SEND_WOKEN           = 1 << 5,
67     HCI_TRANSPORT_LINK_SEND_WAKEUP          = 1 << 6,
68     HCI_TRANSPORT_LINK_SEND_QUEUED_PACKET   = 1 << 7,
69     HCI_TRANSPORT_LINK_SEND_ACK_PACKET      = 1 << 8,
70     HCI_TRANSPORT_LINK_ENTER_SLEEP          = 1 << 9,
71 
72 } hci_transport_link_actions_t;
73 
74 // Configuration Field. No packet buffers -> sliding window = 1, no OOF flow control, support data integrity check
75 #define LINK_CONFIG_SLIDING_WINDOW_SIZE 1
76 #define LINK_CONFIG_OOF_FLOW_CONTROL 0
77 #define LINK_CONFIG_DATA_INTEGRITY_CHECK 1
78 #define LINK_CONFIG_VERSION_NR 0
79 #define LINK_CONFIG_FIELD (LINK_CONFIG_SLIDING_WINDOW_SIZE | (LINK_CONFIG_OOF_FLOW_CONTROL << 3) | (LINK_CONFIG_DATA_INTEGRITY_CHECK << 4) | (LINK_CONFIG_VERSION_NR << 5))
80 
81 // periodic sending during link establishment
82 #define LINK_PERIOD_MS 250
83 
84 // resend wakeup
85 #define LINK_WAKEUP_MS 50
86 
87 // additional packet types
88 #define LINK_ACKNOWLEDGEMENT_TYPE 0x00
89 #define LINK_CONTROL_PACKET_TYPE 0x0f
90 
91 // max size of write requests
92 #define LINK_SLIP_TX_CHUNK_LEN 64
93 
94 // ---
95 static const uint8_t link_control_sync[] =   { 0x01, 0x7e};
96 static const uint8_t link_control_sync_response[] = { 0x02, 0x7d};
97 static const uint8_t link_control_config[] = { 0x03, 0xfc, LINK_CONFIG_FIELD};
98 static const uint8_t link_control_config_prefix_len  = 2;
99 static const uint8_t link_control_config_response[] = { 0x04, 0x7b, LINK_CONFIG_FIELD};
100 static const uint8_t link_control_config_response_prefix_len  = 2;
101 static const uint8_t link_control_wakeup[] = { 0x05, 0xfa};
102 static const uint8_t link_control_woken[] =  { 0x06, 0xf9};
103 static const uint8_t link_control_sleep[] =  { 0x07, 0x78};
104 
105 // max size of link control messages
106 #define LINK_CONTROL_MAX_LEN 3
107 
108 // incoming pre-bufffer + 4 bytes H5 header + max(acl header + acl payload, event header + event data) + 2 bytes opt CRC
109 static uint8_t   hci_packet_with_pre_buffer[HCI_INCOMING_PRE_BUFFER_SIZE + 6 + HCI_PACKET_BUFFER_SIZE];
110 
111 // outgoing slip encoded buffer. +4 to assert that DIC fits in buffer. +1 to assert that last SOF fits in buffer.
112 static uint8_t   slip_outgoing_buffer[LINK_SLIP_TX_CHUNK_LEN+4+1];
113 static uint16_t  slip_outgoing_dic;
114 static uint16_t  slip_outgoing_dic_present;
115 static int       slip_write_active;
116 
117 // H5 Link State
118 static hci_transport_link_state_t link_state;
119 static btstack_timer_source_t link_timer;
120 static uint8_t  link_seq_nr;
121 static uint8_t  link_ack_nr;
122 static uint16_t link_resend_timeout_ms;
123 static uint8_t  link_peer_asleep;
124 static uint8_t  link_peer_supports_data_integrity_check;
125 
126 // auto sleep-mode
127 static btstack_timer_source_t inactivity_timer;
128 static uint16_t link_inactivity_timeout_ms; // auto-sleep if set
129 
130 // Outgoing packet
131 static uint8_t   hci_packet_type;
132 static uint16_t  hci_packet_size;
133 static uint8_t * hci_packet;
134 
135 // hci packet handler
136 static  void (*packet_handler)(uint8_t packet_type, uint8_t *packet, uint16_t size);
137 
138 static int hci_transport_link_actions;
139 
140 // UART Driver + Config
141 static const btstack_uart_block_t * btstack_uart;
142 static btstack_uart_config_t uart_config;
143 static btstack_uart_sleep_mode_t btstack_uart_sleep_mode;
144 
145 // Prototypes
146 static void hci_transport_h5_process_frame(uint16_t frame_size);
147 static int  hci_transport_link_have_outgoing_packet(void);
148 static void hci_transport_link_send_queued_packet(void);
149 static void hci_transport_link_set_timer(uint16_t timeout_ms);
150 static void hci_transport_link_timeout_handler(btstack_timer_source_t * timer);
151 static void hci_transport_link_run(void);
152 static void hci_transport_slip_init(void);
153 
154 // -----------------------------
155 // CRC16-CCITT Calculation - compromise: use 32 byte table - 512 byte table would be faster, but that's too large
156 
157 static const uint16_t crc16_ccitt_table[] ={
158     0x0000, 0x1081, 0x2102, 0x3183,
159     0x4204, 0x5285, 0x6306, 0x7387,
160     0x8408, 0x9489, 0xa50a, 0xb58b,
161     0xc60c, 0xd68d, 0xe70e, 0xf78f
162 };
163 
164 static uint16_t crc16_ccitt_update (uint16_t crc, uint8_t ch){
165     crc = (crc >> 4) ^ crc16_ccitt_table[(crc ^ ch) & 0x000f];
166     crc = (crc >> 4) ^ crc16_ccitt_table[(crc ^ (ch >> 4)) & 0x000f];
167     return crc;
168 }
169 
170 static uint16_t btstack_reverse_bits_16(uint16_t value){
171     int reverse = 0;
172     int i;
173     for (i = 0; i < 16; i++) {
174         reverse = reverse << 1;
175         reverse |= value & 1;
176         value = value >> 1;
177     }
178     return reverse;
179 }
180 
181 static uint16_t crc16_calc_for_slip_frame(const uint8_t * header, const uint8_t * payload, uint16_t len){
182     int i;
183     uint16_t crc = 0xffff;
184     for (i=0 ; i < 4 ; i++){
185         crc = crc16_ccitt_update(crc, header[i]);
186     }
187     for (i=0 ; i < len ; i++){
188         crc = crc16_ccitt_update(crc, payload[i]);
189     }
190     return btstack_reverse_bits_16(crc);
191 }
192 
193 // -----------------------------
194 static void hci_transport_inactivity_timeout_handler(btstack_timer_source_t * ts){
195     log_info("h5: inactivity timeout. link state %d, peer asleep %u, actions 0x%02x, outgoing packet %u",
196         link_state, link_peer_asleep, hci_transport_link_actions, hci_transport_link_have_outgoing_packet());
197     if (hci_transport_link_have_outgoing_packet()) return;
198     if (link_state != LINK_ACTIVE) return;
199     if (hci_transport_link_actions) return;
200     if (link_peer_asleep) return;
201     hci_transport_link_actions |= HCI_TRANSPORT_LINK_SEND_SLEEP;
202     hci_transport_link_run();
203 }
204 
205 static void hci_transport_inactivity_timer_set(void){
206     if (!link_inactivity_timeout_ms) return;
207     btstack_run_loop_set_timer_handler(&inactivity_timer, &hci_transport_inactivity_timeout_handler);
208     btstack_run_loop_set_timer(&inactivity_timer, link_inactivity_timeout_ms);
209     btstack_run_loop_remove_timer(&inactivity_timer);
210     btstack_run_loop_add_timer(&inactivity_timer);
211 }
212 
213 // -----------------------------
214 // SLIP Outgoing
215 
216 // Fill chunk and write
217 static void hci_transport_slip_encode_chunk_and_send(int pos){
218     while (btstack_slip_encoder_has_data() & (pos < LINK_SLIP_TX_CHUNK_LEN)) {
219         slip_outgoing_buffer[pos++] = btstack_slip_encoder_get_byte();
220     }
221 
222     if (!btstack_slip_encoder_has_data()){
223         // Payload encoded, append DIC if present.
224         // note: slip_outgoing_buffer is guaranteed to be big enough to add DIC + SOF after LINK_SLIP_TX_CHUNK_LEN
225         if (slip_outgoing_dic_present){
226             uint8_t dic_buffer[2];
227             big_endian_store_16(dic_buffer, 0, slip_outgoing_dic);
228             btstack_slip_encoder_start(dic_buffer, 2);
229             while (btstack_slip_encoder_has_data()){
230                 slip_outgoing_buffer[pos++] = btstack_slip_encoder_get_byte();
231             }
232         }
233         // Start of Frame
234         slip_outgoing_buffer[pos++] = BTSTACK_SLIP_SOF;
235     }
236     slip_write_active = 1;
237     log_info("hci_transport_slip: send %d bytes", pos);
238     btstack_uart->send_block(slip_outgoing_buffer, pos);
239 }
240 
241 static inline void hci_transport_slip_send_next_chunk(void){
242     hci_transport_slip_encode_chunk_and_send(0);
243 }
244 
245 // format: 0xc0 HEADER PACKET [DIC] 0xc0
246 // @param uint8_t header[4]
247 static void hci_transport_slip_send_frame(const uint8_t * header, const uint8_t * packet, uint16_t packet_size, uint16_t data_integrity_check){
248 
249     int pos = 0;
250 
251     // store data integrity check info
252     slip_outgoing_dic         = data_integrity_check;
253     slip_outgoing_dic_present = header[0] & 0x40;
254 
255     // Start of Frame
256     slip_outgoing_buffer[pos++] = BTSTACK_SLIP_SOF;
257 
258     // Header
259     btstack_slip_encoder_start(header, 4);
260     while (btstack_slip_encoder_has_data()){
261         slip_outgoing_buffer[pos++] = btstack_slip_encoder_get_byte();
262     }
263 
264     // Packet
265     btstack_slip_encoder_start(packet, packet_size);
266 
267     // Fill rest of chunk from packet and send
268     hci_transport_slip_encode_chunk_and_send(pos);
269 }
270 
271 // SLIP Incoming
272 
273 static void hci_transport_slip_init(void){
274     btstack_slip_decoder_init(&hci_packet_with_pre_buffer[HCI_INCOMING_PRE_BUFFER_SIZE], 6 + HCI_PACKET_BUFFER_SIZE);
275 }
276 
277 // H5 Three-Wire Implementation
278 
279 static void hci_transport_link_calc_header(uint8_t * header,
280     uint8_t  sequence_nr,
281     uint8_t  acknowledgement_nr,
282     uint8_t  data_integrity_check_present,
283     uint8_t  reliable_packet,
284     uint8_t  packet_type,
285     uint16_t payload_length){
286 
287     header[0] = sequence_nr | (acknowledgement_nr << 3) | (data_integrity_check_present << 6) | (reliable_packet << 7);
288     header[1] = packet_type | ((payload_length & 0x0f) << 4);
289     header[2] = payload_length >> 4;
290     header[3] = 0xff - (header[0] + header[1] + header[2]);
291 }
292 
293 static void hci_transport_link_send_control(const uint8_t * message, int message_len){
294     uint8_t header[4];
295     hci_transport_link_calc_header(header, 0, 0, link_peer_supports_data_integrity_check, 0, LINK_CONTROL_PACKET_TYPE, message_len);
296     uint16_t data_integrity_check = 0;
297     if (link_peer_supports_data_integrity_check){
298         data_integrity_check = crc16_calc_for_slip_frame(header, message, message_len);
299     }
300     log_info("hci_transport_link_send_control: size %u, append dic %u", message_len, link_peer_supports_data_integrity_check);
301     log_info_hexdump(message, message_len);
302     hci_transport_slip_send_frame(header, message, message_len, data_integrity_check);
303 }
304 
305 static void hci_transport_link_send_sync(void){
306     log_info("link: send sync");
307     hci_transport_link_send_control(link_control_sync, sizeof(link_control_sync));
308 }
309 
310 static void hci_transport_link_send_sync_response(void){
311     log_info("link: send sync response");
312     hci_transport_link_send_control(link_control_sync_response, sizeof(link_control_sync_response));
313 }
314 
315 static void hci_transport_link_send_config(void){
316     log_info("link: send config");
317     hci_transport_link_send_control(link_control_config, sizeof(link_control_config));
318 }
319 
320 static void hci_transport_link_send_config_response(void){
321     log_info("link: send config response");
322     hci_transport_link_send_control(link_control_config_response, sizeof(link_control_config_response));
323 }
324 
325 static void hci_transport_link_send_woken(void){
326     log_info("link: send woken");
327     hci_transport_link_send_control(link_control_woken, sizeof(link_control_woken));
328 }
329 
330 static void hci_transport_link_send_wakeup(void){
331     log_info("link: send wakeup");
332     hci_transport_link_send_control(link_control_wakeup, sizeof(link_control_wakeup));
333 }
334 
335 static void hci_transport_link_send_sleep(void){
336     log_info("link: send sleep");
337     hci_transport_link_send_control(link_control_sleep, sizeof(link_control_sleep));
338 }
339 
340 static void hci_transport_link_send_queued_packet(void){
341 
342     uint8_t header[4];
343     hci_transport_link_calc_header(header, link_seq_nr, link_ack_nr, link_peer_supports_data_integrity_check, 1, hci_packet_type, hci_packet_size);
344 
345     uint16_t data_integrity_check = 0;
346     if (link_peer_supports_data_integrity_check){
347         data_integrity_check = crc16_calc_for_slip_frame(header, hci_packet, hci_packet_size);
348     }
349     log_info("hci_transport_link_send_queued_packet: seq %u, ack %u, size %u. Append dic %u, dic = 0x%04x", link_seq_nr, link_ack_nr, hci_packet_size, link_peer_supports_data_integrity_check, data_integrity_check);
350     log_info_hexdump(hci_packet, hci_packet_size);
351 
352     hci_transport_slip_send_frame(header, hci_packet, hci_packet_size, data_integrity_check);
353 
354     // reset inactvitiy timer
355     hci_transport_inactivity_timer_set();
356 }
357 
358 static void hci_transport_link_send_ack_packet(void){
359     // Pure ACK package is without DIC as there is no payload either
360     log_info("link: send ack %u", link_ack_nr);
361     uint8_t header[4];
362     hci_transport_link_calc_header(header, 0, link_ack_nr, 0, 0, LINK_ACKNOWLEDGEMENT_TYPE, 0);
363     hci_transport_slip_send_frame(header, NULL, 0, 0);
364 }
365 
366 static void hci_transport_link_run(void){
367     // exit if outgoing active
368     if (slip_write_active) return;
369 
370     // process queued requests
371     if (hci_transport_link_actions & HCI_TRANSPORT_LINK_SEND_SYNC){
372         hci_transport_link_actions &= ~HCI_TRANSPORT_LINK_SEND_SYNC;
373         hci_transport_link_send_sync();
374         return;
375     }
376     if (hci_transport_link_actions & HCI_TRANSPORT_LINK_SEND_SYNC_RESPONSE){
377         hci_transport_link_actions &= ~HCI_TRANSPORT_LINK_SEND_SYNC_RESPONSE;
378         hci_transport_link_send_sync_response();
379         return;
380     }
381     if (hci_transport_link_actions & HCI_TRANSPORT_LINK_SEND_CONFIG){
382         hci_transport_link_actions &= ~HCI_TRANSPORT_LINK_SEND_CONFIG;
383         hci_transport_link_send_config();
384         return;
385     }
386     if (hci_transport_link_actions & HCI_TRANSPORT_LINK_SEND_CONFIG_RESPONSE){
387         hci_transport_link_actions &= ~HCI_TRANSPORT_LINK_SEND_CONFIG_RESPONSE;
388         hci_transport_link_send_config_response();
389         return;
390     }
391     if (hci_transport_link_actions & HCI_TRANSPORT_LINK_SEND_WOKEN){
392         hci_transport_link_actions &= ~HCI_TRANSPORT_LINK_SEND_WOKEN;
393         hci_transport_link_send_woken();
394         return;
395     }
396     if (hci_transport_link_actions & HCI_TRANSPORT_LINK_SEND_WAKEUP){
397         hci_transport_link_actions &= ~HCI_TRANSPORT_LINK_SEND_WAKEUP;
398         hci_transport_link_send_wakeup();
399         return;
400     }
401     if (hci_transport_link_actions & HCI_TRANSPORT_LINK_SEND_QUEUED_PACKET){
402         hci_transport_link_actions &= ~HCI_TRANSPORT_LINK_SEND_QUEUED_PACKET;
403         // packet already contains ack, no need to send addtitional one
404         hci_transport_link_actions &= ~HCI_TRANSPORT_LINK_SEND_ACK_PACKET;
405         hci_transport_link_send_queued_packet();
406         return;
407     }
408     if (hci_transport_link_actions & HCI_TRANSPORT_LINK_SEND_ACK_PACKET){
409         hci_transport_link_actions &= ~HCI_TRANSPORT_LINK_SEND_ACK_PACKET;
410         hci_transport_link_send_ack_packet();
411         return;
412     }
413     if (hci_transport_link_actions & HCI_TRANSPORT_LINK_SEND_SLEEP){
414         hci_transport_link_actions &= ~HCI_TRANSPORT_LINK_SEND_SLEEP;
415         hci_transport_link_actions |=  HCI_TRANSPORT_LINK_ENTER_SLEEP;
416         link_peer_asleep = 1;
417         hci_transport_link_send_sleep();
418         return;
419     }
420 }
421 
422 static void hci_transport_link_set_timer(uint16_t timeout_ms){
423     btstack_run_loop_set_timer_handler(&link_timer, &hci_transport_link_timeout_handler);
424     btstack_run_loop_set_timer(&link_timer, timeout_ms);
425     btstack_run_loop_add_timer(&link_timer);
426 }
427 
428 static void hci_transport_link_timeout_handler(btstack_timer_source_t * timer){
429     switch (link_state){
430         case LINK_UNINITIALIZED:
431             hci_transport_link_actions |= HCI_TRANSPORT_LINK_SEND_SYNC;
432             hci_transport_link_set_timer(LINK_PERIOD_MS);
433             break;
434         case LINK_INITIALIZED:
435             hci_transport_link_actions |= HCI_TRANSPORT_LINK_SEND_CONFIG;
436             hci_transport_link_set_timer(LINK_PERIOD_MS);
437             break;
438         case LINK_ACTIVE:
439             if (!hci_transport_link_have_outgoing_packet()){
440                 log_info("h5 timeout while active, but no outgoing packet");
441                 return;
442             }
443             if (link_peer_asleep){
444                 hci_transport_link_actions |= HCI_TRANSPORT_LINK_SEND_WAKEUP;
445                 hci_transport_link_set_timer(LINK_WAKEUP_MS);
446                 return;
447             }
448             // resend packet
449             hci_transport_link_actions |= HCI_TRANSPORT_LINK_SEND_QUEUED_PACKET;
450             hci_transport_link_set_timer(link_resend_timeout_ms);
451             break;
452         default:
453             break;
454     }
455 
456     hci_transport_link_run();
457 }
458 
459 static void hci_transport_link_init(void){
460     link_state = LINK_UNINITIALIZED;
461     link_peer_asleep = 0;
462     link_peer_supports_data_integrity_check = 0;
463 
464     // get started
465     hci_transport_link_actions |= HCI_TRANSPORT_LINK_SEND_SYNC;
466     hci_transport_link_set_timer(LINK_PERIOD_MS);
467     hci_transport_link_run();
468 }
469 
470 static int hci_transport_link_inc_seq_nr(int seq_nr){
471     return (seq_nr + 1) & 0x07;
472 }
473 
474 static int hci_transport_link_have_outgoing_packet(void){
475     return hci_packet != 0;
476 }
477 
478 static void hci_transport_link_clear_queue(void){
479     btstack_run_loop_remove_timer(&link_timer);
480     hci_packet = NULL;
481 }
482 
483 static void hci_transport_h5_queue_packet(uint8_t packet_type, uint8_t *packet, int size){
484     hci_packet = packet;
485     hci_packet_type = packet_type;
486     hci_packet_size = size;
487 }
488 
489 static void hci_transport_h5_emit_sleep_state(int sleep_active){
490     static int last_state = 0;
491     if (sleep_active == last_state) return;
492     last_state = sleep_active;
493 
494     log_info("hci_transport_h5_emit_sleep_state: %u", sleep_active);
495     uint8_t event[3];
496     event[0] = HCI_EVENT_TRANSPORT_SLEEP_MODE;
497     event[1] = sizeof(event) - 2;
498     event[2] = sleep_active;
499     packet_handler(HCI_EVENT_PACKET, &event[0], sizeof(event));
500 }
501 
502 static void hci_transport_h5_process_frame(uint16_t frame_size){
503 
504     if (frame_size < 4) return;
505 
506     uint8_t * slip_header  = &hci_packet_with_pre_buffer[HCI_INCOMING_PRE_BUFFER_SIZE];
507     uint8_t * slip_payload = &hci_packet_with_pre_buffer[HCI_INCOMING_PRE_BUFFER_SIZE + 4];
508     int       frame_size_without_header = frame_size - 4;
509 
510     uint8_t  seq_nr =  slip_header[0] & 0x07;
511     uint8_t  ack_nr = (slip_header[0] >> 3)    & 0x07;
512     uint8_t  data_integrity_check_present = (slip_header[0] & 0x40) != 0;
513     uint8_t  reliable_packet  = (slip_header[0] & 0x80) != 0;
514     uint8_t  link_packet_type = slip_header[1] & 0x0f;
515     uint16_t link_payload_len = (slip_header[1] >> 4) | (slip_header[2] << 4);
516 
517     log_info("hci_transport_h5_process_frame, reliable %u, packet type %u, seq_nr %u, ack_nr %u , dic %u", reliable_packet, link_packet_type, seq_nr, ack_nr, data_integrity_check_present);
518     log_info_hexdump(slip_header, 4);
519     log_info_hexdump(slip_payload, frame_size_without_header);
520 
521     // CSR 8811 does not seem to auto-detect H5 mode and sends data with even parity.
522     // if this byte sequence is detected, just enable even parity
523     const uint8_t sync_response_bcsp[] = {0x01, 0x7a, 0x06, 0x10};
524     if (memcmp(sync_response_bcsp, slip_header, 4) == 0){
525         log_info("h5: detected BSCP SYNC sent with Even Parity -> discard frame and enable Even Parity");
526         btstack_uart->set_parity(1);
527         return;
528     }
529 
530     // validate header checksum
531     uint8_t header_checksum = slip_header[0] + slip_header[1] + slip_header[2] + slip_header[3];
532     if (header_checksum != 0xff){
533         log_info("h5: header checksum 0x%02x (instead of 0xff)", header_checksum);
534         return;
535     }
536 
537     // validate payload length
538     int data_integrity_len = data_integrity_check_present ? 2 : 0;
539     uint16_t received_payload_len = frame_size_without_header - data_integrity_len;
540     if (link_payload_len != received_payload_len){
541         log_info("h5: expected payload len %u but got %u", link_payload_len, received_payload_len);
542         return;
543     }
544 
545     // validate data integrity check
546     if (data_integrity_check_present){
547         uint16_t dic_packet = big_endian_read_16(slip_payload, received_payload_len);
548         uint16_t dic_calculate = crc16_calc_for_slip_frame(slip_header, slip_payload, received_payload_len);
549         if (dic_packet != dic_calculate){
550             log_info("h5: expected dic value 0x%04x but got 0x%04x", dic_calculate, dic_packet);
551             return;
552         }
553     }
554 
555     switch (link_state){
556         case LINK_UNINITIALIZED:
557             if (link_packet_type != LINK_CONTROL_PACKET_TYPE) break;
558             if (memcmp(slip_payload, link_control_sync, sizeof(link_control_sync)) == 0){
559                 log_info("link: received sync");
560                 hci_transport_link_actions |= HCI_TRANSPORT_LINK_SEND_SYNC_RESPONSE;
561             }
562             if (memcmp(slip_payload, link_control_sync_response, sizeof(link_control_sync_response)) == 0){
563                 log_info("link: received sync response");
564                 link_state = LINK_INITIALIZED;
565                 btstack_run_loop_remove_timer(&link_timer);
566                 log_info("link initialized");
567                 //
568                 hci_transport_link_actions |= HCI_TRANSPORT_LINK_SEND_CONFIG;
569                 hci_transport_link_set_timer(LINK_PERIOD_MS);
570             }
571             break;
572         case LINK_INITIALIZED:
573             if (link_packet_type != LINK_CONTROL_PACKET_TYPE) break;
574             if (memcmp(slip_payload, link_control_sync, sizeof(link_control_sync)) == 0){
575                 log_info("link: received sync");
576                 hci_transport_link_actions |= HCI_TRANSPORT_LINK_SEND_SYNC_RESPONSE;
577             }
578             if (memcmp(slip_payload, link_control_config, link_control_config_prefix_len) == 0){
579                 log_info("link: received config, 0x%02x", slip_payload[2]);
580                 hci_transport_link_actions |= HCI_TRANSPORT_LINK_SEND_CONFIG_RESPONSE;
581             }
582             if (memcmp(slip_payload, link_control_config_response, link_control_config_response_prefix_len) == 0){
583                 uint8_t config = slip_payload[2];
584                 link_peer_supports_data_integrity_check = (config & 0x10) != 0;
585                 log_info("link: received config response 0x%02x, data integrity check supported %u", config, link_peer_supports_data_integrity_check);
586                 link_state = LINK_ACTIVE;
587                 btstack_run_loop_remove_timer(&link_timer);
588                 log_info("link activated");
589                 //
590                 link_seq_nr = 0;
591                 link_ack_nr = 0;
592                 // notify upper stack that it can start
593                 uint8_t event[] = { HCI_EVENT_TRANSPORT_PACKET_SENT, 0};
594                 packet_handler(HCI_EVENT_PACKET, &event[0], sizeof(event));
595             }
596             break;
597         case LINK_ACTIVE:
598 
599             // validate packet sequence nr in reliable packets (check for out of sequence error)
600             if (reliable_packet){
601                 if (seq_nr != link_ack_nr){
602                     log_info("expected seq nr %u, but received %u", link_ack_nr, seq_nr);
603                     hci_transport_link_actions |= HCI_TRANSPORT_LINK_SEND_ACK_PACKET;
604                     break;
605                 }
606                 // ack packet right away
607                 link_ack_nr = hci_transport_link_inc_seq_nr(link_ack_nr);
608                 hci_transport_link_actions |= HCI_TRANSPORT_LINK_SEND_ACK_PACKET;
609             }
610 
611             // Process ACKs in reliable packet and explicit ack packets
612             if (reliable_packet || link_packet_type == LINK_ACKNOWLEDGEMENT_TYPE){
613                 // our packet is good if the remote expects our seq nr + 1
614                 int next_seq_nr = hci_transport_link_inc_seq_nr(link_seq_nr);
615                 if (hci_transport_link_have_outgoing_packet() && next_seq_nr == ack_nr){
616                     log_info("h5: outoing packet with seq %u ack'ed", link_seq_nr);
617                     link_seq_nr = next_seq_nr;
618                     hci_transport_link_clear_queue();
619 
620                     // notify upper stack that it can send again
621                     uint8_t event[] = { HCI_EVENT_TRANSPORT_PACKET_SENT, 0};
622                     packet_handler(HCI_EVENT_PACKET, &event[0], sizeof(event));
623                 }
624             }
625 
626             switch (link_packet_type){
627                 case LINK_CONTROL_PACKET_TYPE:
628                     if (memcmp(slip_payload, link_control_config, sizeof(link_control_config)) == 0){
629                         log_info("link: received config");
630                         hci_transport_link_actions |= HCI_TRANSPORT_LINK_SEND_CONFIG_RESPONSE;
631                         break;
632                     }
633                     if (memcmp(slip_payload, link_control_sync, sizeof(link_control_sync)) == 0){
634                         log_info("link: received sync in ACTIVE STATE!");
635                         // TODO sync during active indicates peer reset -> full upper layer reset necessary
636                         break;
637                     }
638                     if (memcmp(slip_payload, link_control_sleep, sizeof(link_control_sleep)) == 0){
639                         if (btstack_uart_sleep_mode){
640                             log_info("link: received sleep message. Enabling UART Sleep.");
641                             btstack_uart->set_sleep(btstack_uart_sleep_mode);
642                             hci_transport_h5_emit_sleep_state(1);
643                         } else {
644                             log_info("link: received sleep message. UART Sleep not supported");
645                         }
646                         link_peer_asleep = 1;
647                         break;
648                     }
649                     if (memcmp(slip_payload, link_control_wakeup, sizeof(link_control_wakeup)) == 0){
650                         log_info("link: received wakupe message -> send woken");
651                         link_peer_asleep = 0;
652                         hci_transport_link_actions |= HCI_TRANSPORT_LINK_SEND_WOKEN;
653                         break;
654                     }
655                     if (memcmp(slip_payload, link_control_woken, sizeof(link_control_woken)) == 0){
656                         log_info("link: received woken message");
657                         link_peer_asleep = 0;
658                         // queued packet will be sent in hci_transport_link_run if needed
659                         break;
660                     }
661                     break;
662                 case HCI_EVENT_PACKET:
663                 case HCI_ACL_DATA_PACKET:
664                 case HCI_SCO_DATA_PACKET:
665                     // seems like peer is awake
666                     link_peer_asleep = 0;
667                     // forward packet to stack
668                     packet_handler(link_packet_type, slip_payload, link_payload_len);
669                     // reset inactvitiy timer
670                     hci_transport_inactivity_timer_set();
671                     break;
672             }
673 
674             break;
675         default:
676             break;
677     }
678 
679     hci_transport_link_run();
680 }
681 
682 // recommendet time until resend: 3 * time of largest packet
683 static uint16_t hci_transport_link_calc_resend_timeout(uint32_t baudrate){
684     uint32_t max_packet_size_in_bit = (HCI_PACKET_BUFFER_SIZE + 6) << 3;
685     uint32_t t_max_x3_ms = max_packet_size_in_bit * 3000 / baudrate;
686     log_info("resend timeout for %u baud: %u ms", baudrate, t_max_x3_ms);
687     return t_max_x3_ms;
688 }
689 
690 static void hci_transport_link_update_resend_timeout(uint32_t baudrate){
691     link_resend_timeout_ms = hci_transport_link_calc_resend_timeout(baudrate);
692 }
693 
694 /// H5 Interface
695 
696 static uint8_t hci_transport_link_read_byte;
697 
698 static void hci_transport_h5_read_next_byte(void){
699     log_debug("h5: rx nxt");
700     btstack_uart->receive_block(&hci_transport_link_read_byte, 1);
701 }
702 
703 static void hci_transport_h5_block_received(){
704     log_debug("slip: process 0x%02x", hci_transport_link_read_byte);
705     btstack_slip_decoder_process(hci_transport_link_read_byte);
706     uint16_t frame_size = btstack_slip_decoder_frame_size();
707     if (frame_size) {
708         hci_transport_h5_process_frame(frame_size);
709         hci_transport_slip_init();
710     }
711     hci_transport_h5_read_next_byte();
712 }
713 
714 static void hci_transport_h5_block_sent(void){
715 
716     // check if more data to send
717     if (btstack_slip_encoder_has_data()){
718         hci_transport_slip_send_next_chunk();
719         return;
720     }
721 
722     // done
723     slip_write_active = 0;
724 
725     // enter sleep mode after sending sleep message
726     if (hci_transport_link_actions & HCI_TRANSPORT_LINK_ENTER_SLEEP){
727         hci_transport_link_actions &= ~HCI_TRANSPORT_LINK_ENTER_SLEEP;
728         if (btstack_uart_sleep_mode){
729             log_info("link: sent sleep message. Enabling UART Sleep.");
730             btstack_uart->set_sleep(btstack_uart_sleep_mode);
731         } else {
732             log_info("link: sent sleep message. UART Sleep not supported");
733         }
734         hci_transport_h5_emit_sleep_state(1);
735     }
736 
737     hci_transport_link_run();
738 }
739 
740 static void hci_transport_h5_init(const void * transport_config){
741     // check for hci_transport_config_uart_t
742     if (!transport_config) {
743         log_error("hci_transport_h5: no config!");
744         return;
745     }
746     if (((hci_transport_config_t*)transport_config)->type != HCI_TRANSPORT_CONFIG_UART) {
747         log_error("hci_transport_h5: config not of type != HCI_TRANSPORT_CONFIG_UART!");
748         return;
749     }
750 
751     // extract UART config from transport config
752     hci_transport_config_uart_t * hci_transport_config_uart = (hci_transport_config_uart_t*) transport_config;
753     uart_config.baudrate    = hci_transport_config_uart->baudrate_init;
754     uart_config.flowcontrol = hci_transport_config_uart->flowcontrol;
755     uart_config.device_name = hci_transport_config_uart->device_name;
756 
757     // setup UART driver
758     btstack_uart->init(&uart_config);
759     btstack_uart->set_block_received(&hci_transport_h5_block_received);
760     btstack_uart->set_block_sent(&hci_transport_h5_block_sent);
761 }
762 
763 static int hci_transport_h5_open(void){
764     int res = btstack_uart->open();
765     if (res){
766         return res;
767     }
768 
769     // check if wake on RX can be used
770     btstack_uart_sleep_mode = BTSTACK_UART_SLEEP_OFF;
771     int supported_sleep_modes = 0;
772     if (btstack_uart->get_supported_sleep_modes){
773         supported_sleep_modes = btstack_uart->get_supported_sleep_modes();
774     }
775     if (supported_sleep_modes & BTSTACK_UART_SLEEP_MASK_RTS_LOW_WAKE_ON_RX_EDGE){
776         log_info("H5: using wake on RX");
777         btstack_uart_sleep_mode = BTSTACK_UART_SLEEP_RTS_LOW_WAKE_ON_RX_EDGE;
778     } else {
779         log_info("H5: UART driver does not provide compatible sleep mode");
780     }
781 
782     // setup resend timeout
783     hci_transport_link_update_resend_timeout(uart_config.baudrate);
784 
785     // init slip parser state machine
786     hci_transport_slip_init();
787 
788     // init link management - already starts syncing
789     hci_transport_link_init();
790 
791     // start receiving
792     hci_transport_h5_read_next_byte();
793 
794     return 0;
795 }
796 
797 static int hci_transport_h5_close(void){
798     return btstack_uart->close();
799     return 0;
800 }
801 
802 static void hci_transport_h5_register_packet_handler(void (*handler)(uint8_t packet_type, uint8_t *packet, uint16_t size)){
803     packet_handler = handler;
804 }
805 
806 static int hci_transport_h5_can_send_packet_now(uint8_t packet_type){
807     int res = !hci_transport_link_have_outgoing_packet() && link_state == LINK_ACTIVE;
808     // log_info("hci_transport_h5_can_send_packet_now: %u", res);
809     return res;
810 }
811 
812 static int hci_transport_h5_send_packet(uint8_t packet_type, uint8_t *packet, int size){
813     if (!hci_transport_h5_can_send_packet_now(packet_type)){
814         log_error("hci_transport_h5_send_packet called but in state %d", link_state);
815         return -1;
816     }
817 
818     // store request
819     hci_transport_h5_queue_packet(packet_type, packet, size);
820 
821     // send wakeup first
822     if (link_peer_asleep){
823         hci_transport_h5_emit_sleep_state(0);
824         if (btstack_uart_sleep_mode){
825             log_info("h5: disable UART sleep");
826             btstack_uart->set_sleep(BTSTACK_UART_SLEEP_OFF);
827         }
828         hci_transport_link_actions |= HCI_TRANSPORT_LINK_SEND_WAKEUP;
829         hci_transport_link_set_timer(LINK_WAKEUP_MS);
830     } else {
831         hci_transport_link_actions |= HCI_TRANSPORT_LINK_SEND_QUEUED_PACKET;
832         hci_transport_link_set_timer(link_resend_timeout_ms);
833     }
834     hci_transport_link_run();
835     return 0;
836 }
837 
838 static int hci_transport_h5_set_baudrate(uint32_t baudrate){
839 
840     log_info("hci_transport_h5_set_baudrate %u", baudrate);
841     int res = btstack_uart->set_baudrate(baudrate);
842 
843     if (res) return res;
844     hci_transport_link_update_resend_timeout(baudrate);
845     return 0;
846 }
847 
848 static void hci_transport_h5_reset_link(void){
849 
850     log_info("hci_transport_h5_reset_link");
851 
852     // clear outgoing queue
853     hci_transport_link_clear_queue();
854 
855     // init slip parser state machine
856     hci_transport_slip_init();
857 
858     // init link management - already starts syncing
859     hci_transport_link_init();
860 }
861 
862 static const hci_transport_t hci_transport_h5 = {
863     /* const char * name; */                                        "H5",
864     /* void   (*init) (const void *transport_config); */            &hci_transport_h5_init,
865     /* int    (*open)(void); */                                     &hci_transport_h5_open,
866     /* int    (*close)(void); */                                    &hci_transport_h5_close,
867     /* void   (*register_packet_handler)(void (*handler)(...); */   &hci_transport_h5_register_packet_handler,
868     /* int    (*can_send_packet_now)(uint8_t packet_type); */       &hci_transport_h5_can_send_packet_now,
869     /* int    (*send_packet)(...); */                               &hci_transport_h5_send_packet,
870     /* int    (*set_baudrate)(uint32_t baudrate); */                &hci_transport_h5_set_baudrate,
871     /* void   (*reset_link)(void); */                               &hci_transport_h5_reset_link,
872     /* void   (*set_sco_config)(uint16_t voice_setting, int num_connections); */ NULL,
873 };
874 
875 // configure and return h5 singleton
876 const hci_transport_t * hci_transport_h5_instance(const btstack_uart_block_t * uart_driver) {
877     btstack_uart = uart_driver;
878     return &hci_transport_h5;
879 }
880 
881 void hci_transport_h5_set_auto_sleep(uint16_t inactivity_timeout_ms){
882     link_inactivity_timeout_ms = inactivity_timeout_ms;
883 }
884