xref: /btstack/src/hci_transport_h5.c (revision bc37f7b0d0a3eaa5763a873c5730bc14b849aaa0)
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 /*
39  *  hci_transport_h5.c
40  *
41  *  HCI Transport API implementation for basic H5 protocol
42  *
43  *  Created by Matthias Ringwald on 4/29/09.
44  */
45 
46 #include "hci.h"
47 #include "btstack_slip.h"
48 #include "btstack_debug.h"
49 #include "hci_transport.h"
50 #include "btstack_uart_block.h"
51 
52 typedef enum {
53     LINK_UNINITIALIZED,
54     LINK_INITIALIZED,
55     LINK_ACTIVE
56 } hci_transport_link_state_t;
57 
58 typedef enum {
59     HCI_TRANSPORT_LINK_SEND_SYNC            = 1 << 0,
60     HCI_TRANSPORT_LINK_SEND_SYNC_RESPONSE   = 1 << 1,
61     HCI_TRANSPORT_LINK_SEND_CONFIG          = 1 << 2,
62     HCI_TRANSPORT_LINK_SEND_CONFIG_RESPONSE = 1 << 3,
63     HCI_TRANSPORT_LINK_SEND_SLEEP           = 1 << 4,
64     HCI_TRANSPORT_LINK_SEND_WOKEN           = 1 << 5,
65     HCI_TRANSPORT_LINK_SEND_WAKEUP          = 1 << 6,
66     HCI_TRANSPORT_LINK_SEND_QUEUED_PACKET   = 1 << 7,
67     HCI_TRANSPORT_LINK_SEND_ACK_PACKET      = 1 << 8,
68     HCI_TRANSPORT_LINK_ENTER_SLEEP          = 1 << 9,
69 
70 } hci_transport_link_actions_t;
71 
72 // Configuration Field. No packet buffers -> sliding window = 1, no OOF flow control, no data integrity check
73 #define LINK_CONFIG_SLIDING_WINDOW_SIZE 1
74 #define LINK_CONFIG_OOF_FLOW_CONTROL 0
75 #define LINK_CONFIG_DATA_INTEGRITY_CHECK 0
76 #define LINK_CONFIG_VERSION_NR 0
77 #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))
78 
79 // periodic sending during link establishment
80 #define LINK_PERIOD_MS 250
81 
82 // resend wakeup
83 #define LINK_WAKEUP_MS 50
84 
85 // additional packet types
86 #define LINK_ACKNOWLEDGEMENT_TYPE 0x00
87 #define LINK_CONTROL_PACKET_TYPE 0x0f
88 
89 // max size of write requests
90 #define LINK_SLIP_TX_CHUNK_LEN 64
91 
92 // ---
93 static const uint8_t link_control_sync[] =   { 0x01, 0x7e};
94 static const uint8_t link_control_sync_response[] = { 0x02, 0x7d};
95 static const uint8_t link_control_config[] = { 0x03, 0xfc, LINK_CONFIG_FIELD};
96 static const uint8_t link_control_config_prefix_len  = 2;
97 static const uint8_t link_control_config_response[] = { 0x04, 0x7b, LINK_CONFIG_FIELD};
98 static const uint8_t link_control_config_response_prefix_len  = 2;
99 static const uint8_t link_control_wakeup[] = { 0x05, 0xfa};
100 static const uint8_t link_control_woken[] =  { 0x06, 0xf9};
101 static const uint8_t link_control_sleep[] =  { 0x07, 0x78};
102 
103 // incoming pre-bufffer + 4 bytes H5 header + max(acl header + acl payload, event header + event data) + 2 bytes opt CRC
104 static uint8_t   hci_packet_with_pre_buffer[HCI_INCOMING_PRE_BUFFER_SIZE + 6 + HCI_PACKET_BUFFER_SIZE];
105 
106 // outgoing slip encoded buffer. +1 to assert that last SOF fits in buffer
107 static uint8_t slip_outgoing_buffer[LINK_SLIP_TX_CHUNK_LEN+1];
108 static int     slip_write_active;
109 
110 // H5 Link State
111 static hci_transport_link_state_t link_state;
112 static btstack_timer_source_t link_timer;
113 static uint8_t  link_seq_nr;
114 static uint8_t  link_ack_nr;
115 static uint16_t link_resend_timeout_ms;
116 static uint8_t  link_peer_asleep;
117 
118 // auto sleep-mode
119 static btstack_timer_source_t inactivity_timer;
120 static uint16_t link_inactivity_timeout_ms; // auto-sleep if set
121 
122 // Outgoing packet
123 static uint8_t   hci_packet_type;
124 static uint16_t  hci_packet_size;
125 static uint8_t * hci_packet;
126 
127 // hci packet handler
128 static  void (*packet_handler)(uint8_t packet_type, uint8_t *packet, uint16_t size);
129 
130 static int hci_transport_link_actions;
131 
132 // UART Driver + Config
133 static const btstack_uart_block_t * btstack_uart;
134 static btstack_uart_config_t uart_config;
135 static btstack_uart_sleep_mode_t btstack_uart_sleep_mode;
136 
137 // Prototypes
138 static void hci_transport_h5_process_frame(uint16_t frame_size);
139 static int  hci_transport_link_have_outgoing_packet(void);
140 static void hci_transport_link_send_queued_packet(void);
141 static void hci_transport_link_set_timer(uint16_t timeout_ms);
142 static void hci_transport_link_timeout_handler(btstack_timer_source_t * timer);
143 static void hci_transport_link_run(void);
144 static void hci_transport_slip_init(void);
145 
146 // -----------------------------
147 static void hci_transport_inactivity_timeout_handler(btstack_timer_source_t * ts){
148     log_info("h5: inactivity timeout. link state %u, peer asleep %u, actions 0x%02x, outgoing packet %u",
149         link_state, link_peer_asleep, hci_transport_link_actions, hci_transport_link_have_outgoing_packet());
150     if (hci_transport_link_have_outgoing_packet()) return;
151     if (link_state != LINK_ACTIVE) return;
152     if (hci_transport_link_actions) return;
153     if (link_peer_asleep) return;
154     hci_transport_link_actions |= HCI_TRANSPORT_LINK_SEND_SLEEP;
155     hci_transport_link_run();
156 }
157 
158 static void hci_transport_inactivity_timer_set(void){
159     if (!link_inactivity_timeout_ms) return;
160     btstack_run_loop_set_timer_handler(&inactivity_timer, &hci_transport_inactivity_timeout_handler);
161     btstack_run_loop_set_timer(&inactivity_timer, link_inactivity_timeout_ms);
162     btstack_run_loop_remove_timer(&inactivity_timer);
163     btstack_run_loop_add_timer(&inactivity_timer);
164 }
165 
166 // -----------------------------
167 // SLIP Outgoing
168 
169 // Fill chunk and write
170 static void hci_transport_slip_encode_chunk_and_send(int pos){
171     while (btstack_slip_encoder_has_data() & (pos < LINK_SLIP_TX_CHUNK_LEN)) {
172         slip_outgoing_buffer[pos++] = btstack_slip_encoder_get_byte();
173     }
174     if (!btstack_slip_encoder_has_data()){
175         // Start of Frame
176         slip_outgoing_buffer[pos++] = BTSTACK_SLIP_SOF;
177     }
178     slip_write_active = 1;
179     log_info("hci_transport_slip: send %u bytes", pos);
180     btstack_uart->send_block(slip_outgoing_buffer, pos);
181 }
182 
183 static inline void hci_transport_slip_send_next_chunk(void){
184     hci_transport_slip_encode_chunk_and_send(0);
185 }
186 
187 // format: 0xc0 HEADER PACKER 0xc0
188 // @param uint8_t header[4]
189 static void hci_transport_slip_send_frame(const uint8_t * header, const uint8_t * packet, uint16_t packet_size){
190 
191     int pos = 0;
192 
193     // Start of Frame
194     slip_outgoing_buffer[pos++] = BTSTACK_SLIP_SOF;
195 
196     // Header
197     btstack_slip_encoder_start(header, 4);
198     while (btstack_slip_encoder_has_data()){
199         slip_outgoing_buffer[pos++] = btstack_slip_encoder_get_byte();
200     }
201 
202     // Packet
203     btstack_slip_encoder_start(packet, packet_size);
204 
205     // Fill rest of chunk from packet and send
206     hci_transport_slip_encode_chunk_and_send(pos);
207 }
208 
209 // SLIP Incoming
210 
211 static void hci_transport_slip_init(void){
212     btstack_slip_decoder_init(&hci_packet_with_pre_buffer[HCI_INCOMING_PRE_BUFFER_SIZE], 6 + HCI_PACKET_BUFFER_SIZE);
213 }
214 
215 // H5 Three-Wire Implementation
216 
217 static void hci_transport_link_calc_header(uint8_t * header,
218     uint8_t  sequence_nr,
219     uint8_t  acknowledgement_nr,
220     uint8_t  data_integrity_check_present,
221     uint8_t  reliable_packet,
222     uint8_t  packet_type,
223     uint16_t payload_length){
224 
225     // reset data integrity flag
226     if (data_integrity_check_present){
227         log_error("hci_transport_link_calc_header: data integrity not supported, dropping flag");
228         data_integrity_check_present = 0;
229     }
230 
231     header[0] = sequence_nr | (acknowledgement_nr << 3) | (data_integrity_check_present << 6) | (reliable_packet << 7);
232     header[1] = packet_type | ((payload_length & 0x0f) << 4);
233     header[2] = payload_length >> 4;
234     header[3] = 0xff - (header[0] + header[1] + header[2]);
235 }
236 
237 static void hci_transport_link_send_control(const uint8_t * message, int message_len){
238     uint8_t header[4];
239     hci_transport_link_calc_header(header, 0, 0, 0, 0, LINK_CONTROL_PACKET_TYPE, message_len);
240     hci_transport_slip_send_frame(header, message, message_len);
241 }
242 
243 static void hci_transport_link_send_sync(void){
244     log_info("link: send sync");
245     hci_transport_link_send_control(link_control_sync, sizeof(link_control_sync));
246 }
247 
248 static void hci_transport_link_send_sync_response(void){
249     log_info("link: send sync response");
250     hci_transport_link_send_control(link_control_sync_response, sizeof(link_control_sync_response));
251 }
252 
253 static void hci_transport_link_send_config(void){
254     log_info("link: send config");
255     hci_transport_link_send_control(link_control_config, sizeof(link_control_config));
256 }
257 
258 static void hci_transport_link_send_config_response(void){
259     log_info("link: send config response");
260     hci_transport_link_send_control(link_control_config_response, sizeof(link_control_config_response));
261 }
262 
263 static void hci_transport_link_send_woken(void){
264     log_info("link: send woken");
265     hci_transport_link_send_control(link_control_woken, sizeof(link_control_woken));
266 }
267 
268 static void hci_transport_link_send_wakeup(void){
269     log_info("link: send wakeup");
270     hci_transport_link_send_control(link_control_wakeup, sizeof(link_control_wakeup));
271 }
272 
273 static void hci_transport_link_send_sleep(void){
274     log_info("link: send sleep");
275     hci_transport_link_send_control(link_control_sleep, sizeof(link_control_sleep));
276 }
277 
278 static void hci_transport_link_send_queued_packet(void){
279     log_info("hci_transport_link_send_queued_packet: seq %u, ack %u, size %u", link_seq_nr, link_ack_nr, hci_packet_size);
280     log_info_hexdump(hci_packet, hci_packet_size);
281 
282     uint8_t header[4];
283     hci_transport_link_calc_header(header, link_seq_nr, link_ack_nr, 0, 1, hci_packet_type, hci_packet_size);
284     hci_transport_slip_send_frame(header, hci_packet, hci_packet_size);
285 
286     // reset inactvitiy timer
287     hci_transport_inactivity_timer_set();
288 }
289 
290 static void hci_transport_link_send_ack_packet(void){
291     log_info("link: send ack %u", link_ack_nr);
292     uint8_t header[4];
293     hci_transport_link_calc_header(header, 0, link_ack_nr, 0, 0, LINK_ACKNOWLEDGEMENT_TYPE, 0);
294     hci_transport_slip_send_frame(header, NULL, 0);
295 }
296 
297 static void hci_transport_link_run(void){
298     // exit if outgoing active
299     if (slip_write_active) return;
300 
301     // process queued requests
302     if (hci_transport_link_actions & HCI_TRANSPORT_LINK_SEND_SYNC){
303         hci_transport_link_actions &= ~HCI_TRANSPORT_LINK_SEND_SYNC;
304         hci_transport_link_send_sync();
305         return;
306     }
307     if (hci_transport_link_actions & HCI_TRANSPORT_LINK_SEND_SYNC_RESPONSE){
308         hci_transport_link_actions &= ~HCI_TRANSPORT_LINK_SEND_SYNC_RESPONSE;
309         hci_transport_link_send_sync_response();
310         return;
311     }
312     if (hci_transport_link_actions & HCI_TRANSPORT_LINK_SEND_CONFIG){
313         hci_transport_link_actions &= ~HCI_TRANSPORT_LINK_SEND_CONFIG;
314         hci_transport_link_send_config();
315         return;
316     }
317     if (hci_transport_link_actions & HCI_TRANSPORT_LINK_SEND_CONFIG_RESPONSE){
318         hci_transport_link_actions &= ~HCI_TRANSPORT_LINK_SEND_CONFIG_RESPONSE;
319         hci_transport_link_send_config_response();
320         return;
321     }
322     if (hci_transport_link_actions & HCI_TRANSPORT_LINK_SEND_WOKEN){
323         hci_transport_link_actions &= ~HCI_TRANSPORT_LINK_SEND_WOKEN;
324         hci_transport_link_send_woken();
325         return;
326     }
327     if (hci_transport_link_actions & HCI_TRANSPORT_LINK_SEND_WAKEUP){
328         hci_transport_link_actions &= ~HCI_TRANSPORT_LINK_SEND_WAKEUP;
329         hci_transport_link_send_wakeup();
330         return;
331     }
332     if (hci_transport_link_actions & HCI_TRANSPORT_LINK_SEND_QUEUED_PACKET){
333         hci_transport_link_actions &= ~HCI_TRANSPORT_LINK_SEND_QUEUED_PACKET;
334         // packet already contains ack, no need to send addtitional one
335         hci_transport_link_actions &= ~HCI_TRANSPORT_LINK_SEND_ACK_PACKET;
336         hci_transport_link_send_queued_packet();
337         return;
338     }
339     if (hci_transport_link_actions & HCI_TRANSPORT_LINK_SEND_ACK_PACKET){
340         hci_transport_link_actions &= ~HCI_TRANSPORT_LINK_SEND_ACK_PACKET;
341         hci_transport_link_send_ack_packet();
342         return;
343     }
344     if (hci_transport_link_actions & HCI_TRANSPORT_LINK_SEND_SLEEP){
345         hci_transport_link_actions &= ~HCI_TRANSPORT_LINK_SEND_SLEEP;
346         hci_transport_link_actions |=  HCI_TRANSPORT_LINK_ENTER_SLEEP;
347         link_peer_asleep = 1;
348         hci_transport_link_send_sleep();
349         return;
350     }
351 }
352 
353 static void hci_transport_link_set_timer(uint16_t timeout_ms){
354     btstack_run_loop_set_timer_handler(&link_timer, &hci_transport_link_timeout_handler);
355     btstack_run_loop_set_timer(&link_timer, timeout_ms);
356     btstack_run_loop_add_timer(&link_timer);
357 }
358 
359 static void hci_transport_link_timeout_handler(btstack_timer_source_t * timer){
360     switch (link_state){
361         case LINK_UNINITIALIZED:
362             hci_transport_link_actions |= HCI_TRANSPORT_LINK_SEND_SYNC;
363             hci_transport_link_set_timer(LINK_PERIOD_MS);
364             break;
365         case LINK_INITIALIZED:
366             hci_transport_link_actions |= HCI_TRANSPORT_LINK_SEND_CONFIG;
367             hci_transport_link_set_timer(LINK_PERIOD_MS);
368             break;
369         case LINK_ACTIVE:
370             if (!hci_transport_link_have_outgoing_packet()){
371                 log_info("h5 timeout while active, but no outgoing packet");
372                 return;
373             }
374             if (link_peer_asleep){
375                 hci_transport_link_actions |= HCI_TRANSPORT_LINK_SEND_WAKEUP;
376                 hci_transport_link_set_timer(LINK_WAKEUP_MS);
377                 return;
378             }
379             // resend packet
380             hci_transport_link_actions |= HCI_TRANSPORT_LINK_SEND_QUEUED_PACKET;
381             hci_transport_link_set_timer(link_resend_timeout_ms);
382             break;
383         default:
384             break;
385     }
386 
387     hci_transport_link_run();
388 }
389 
390 static void hci_transport_link_init(void){
391     link_state = LINK_UNINITIALIZED;
392     link_peer_asleep = 0;
393 
394     // get started
395     hci_transport_link_actions |= HCI_TRANSPORT_LINK_SEND_SYNC;
396     hci_transport_link_set_timer(LINK_PERIOD_MS);
397     hci_transport_link_run();
398 }
399 
400 static int hci_transport_link_inc_seq_nr(int seq_nr){
401     return (seq_nr + 1) & 0x07;
402 }
403 
404 static int hci_transport_link_have_outgoing_packet(void){
405     return hci_packet != 0;
406 }
407 
408 static void hci_transport_link_clear_queue(void){
409     btstack_run_loop_remove_timer(&link_timer);
410     hci_packet = NULL;
411 }
412 
413 static void hci_transport_h5_queue_packet(uint8_t packet_type, uint8_t *packet, int size){
414     hci_packet = packet;
415     hci_packet_type = packet_type;
416     hci_packet_size = size;
417 }
418 
419 static void hci_transport_h5_process_frame(uint16_t frame_size){
420 
421     if (frame_size < 4) return;
422 
423     uint8_t * slip_header  = &hci_packet_with_pre_buffer[HCI_INCOMING_PRE_BUFFER_SIZE];
424     uint8_t * slip_payload = &hci_packet_with_pre_buffer[HCI_INCOMING_PRE_BUFFER_SIZE + 4];
425     int       frame_size_without_header = frame_size - 4;
426 
427     int      seq_nr =  slip_header[0] & 0x07;
428     int      ack_nr = (slip_header[0] >> 3)    & 0x07;
429     int      data_integrity_check_present = (slip_header[0] & 0x40) != 0;
430     int      reliable_packet  = (slip_header[0] & 0x80) != 0;
431     uint8_t  link_packet_type = slip_header[1] & 0x0f;
432     uint16_t link_payload_len = (slip_header[1] >> 4) | (slip_header[2] << 4);
433 
434     log_info("hci_transport_h5_process_frame, reliable %u, packet type %u, seq_nr %u, ack_nr %u", reliable_packet, link_packet_type, seq_nr, ack_nr);
435     log_info_hexdump(slip_header, 4);
436     log_info_hexdump(slip_payload, frame_size_without_header);
437 
438     // CSR 8811 does not seem to auto-detect H5 mode and sends data with even parity.
439     // if this byte sequence is detected, just enable even parity
440     const uint8_t sync_response_bcsp[] = {0x01, 0x7a, 0x06, 0x10};
441     if (memcmp(sync_response_bcsp, slip_header, 4) == 0){
442         log_info("h5: detected BSCP SYNC sent with Even Parity -> discard frame and enable Even Parity");
443         btstack_uart->set_parity(1);
444         return;
445     }
446 
447     // validate header checksum
448     uint8_t header_checksum = slip_header[0] + slip_header[1] + slip_header[2] + slip_header[3];
449     if (header_checksum != 0xff){
450         log_info("h5: header checksum 0x%02x (instead of 0xff)", header_checksum);
451         return;
452     }
453 
454     // validate payload length
455     int data_integrity_len = data_integrity_check_present ? 2 : 0;
456     uint16_t received_payload_len = frame_size_without_header - data_integrity_len;
457     if (link_payload_len != received_payload_len){
458         log_info("h5: expected payload len %u but got %u", link_payload_len, received_payload_len);
459         return;
460     }
461 
462     // (TODO data integrity check)
463 
464     switch (link_state){
465         case LINK_UNINITIALIZED:
466             if (link_packet_type != LINK_CONTROL_PACKET_TYPE) break;
467             if (memcmp(slip_payload, link_control_sync, sizeof(link_control_sync)) == 0){
468                 log_info("link: received sync");
469                 hci_transport_link_actions |= HCI_TRANSPORT_LINK_SEND_SYNC_RESPONSE;
470             }
471             if (memcmp(slip_payload, link_control_sync_response, sizeof(link_control_sync_response)) == 0){
472                 log_info("link: received sync response");
473                 link_state = LINK_INITIALIZED;
474                 btstack_run_loop_remove_timer(&link_timer);
475                 log_info("link initialized");
476                 //
477                 hci_transport_link_actions |= HCI_TRANSPORT_LINK_SEND_CONFIG;
478                 hci_transport_link_set_timer(LINK_PERIOD_MS);
479             }
480             break;
481         case LINK_INITIALIZED:
482             if (link_packet_type != LINK_CONTROL_PACKET_TYPE) break;
483             if (memcmp(slip_payload, link_control_sync, sizeof(link_control_sync)) == 0){
484                 log_info("link: received sync");
485                 hci_transport_link_actions |= HCI_TRANSPORT_LINK_SEND_SYNC_RESPONSE;
486             }
487             if (memcmp(slip_payload, link_control_config, link_control_config_prefix_len) == 0){
488                 log_info("link: received config");
489                 hci_transport_link_actions |= HCI_TRANSPORT_LINK_SEND_CONFIG_RESPONSE;
490             }
491             if (memcmp(slip_payload, link_control_config_response, link_control_config_response_prefix_len) == 0){
492                 log_info("link: received config response");
493                 link_state = LINK_ACTIVE;
494                 btstack_run_loop_remove_timer(&link_timer);
495                 log_info("link activated");
496                 //
497                 link_seq_nr = 0;
498                 link_ack_nr = 0;
499                 // notify upper stack that it can start
500                 uint8_t event[] = { HCI_EVENT_TRANSPORT_PACKET_SENT, 0};
501                 packet_handler(HCI_EVENT_PACKET, &event[0], sizeof(event));
502             }
503             break;
504         case LINK_ACTIVE:
505 
506             // validate packet sequence nr in reliable packets (check for out of sequence error)
507             if (reliable_packet){
508                 if (seq_nr != link_ack_nr){
509                     log_info("expected seq nr %u, but received %u", link_ack_nr, seq_nr);
510                     hci_transport_link_actions |= HCI_TRANSPORT_LINK_SEND_ACK_PACKET;
511                     break;
512                 }
513                 // ack packet right away
514                 link_ack_nr = hci_transport_link_inc_seq_nr(link_ack_nr);
515                 hci_transport_link_actions |= HCI_TRANSPORT_LINK_SEND_ACK_PACKET;
516             }
517 
518             // Process ACKs in reliable packet and explicit ack packets
519             if (reliable_packet || link_packet_type == LINK_ACKNOWLEDGEMENT_TYPE){
520                 // our packet is good if the remote expects our seq nr + 1
521                 int next_seq_nr = hci_transport_link_inc_seq_nr(link_seq_nr);
522                 if (hci_transport_link_have_outgoing_packet() && next_seq_nr == ack_nr){
523                     log_info("h5: outoing packet with seq %u ack'ed", link_seq_nr);
524                     link_seq_nr = next_seq_nr;
525                     hci_transport_link_clear_queue();
526 
527                     // notify upper stack that it can send again
528                     uint8_t event[] = { HCI_EVENT_TRANSPORT_PACKET_SENT, 0};
529                     packet_handler(HCI_EVENT_PACKET, &event[0], sizeof(event));
530                 }
531             }
532 
533             switch (link_packet_type){
534                 case LINK_CONTROL_PACKET_TYPE:
535                     if (memcmp(slip_payload, link_control_config, sizeof(link_control_config)) == 0){
536                         log_info("link: received config");
537                         hci_transport_link_actions |= HCI_TRANSPORT_LINK_SEND_CONFIG_RESPONSE;
538                         break;
539                     }
540                     if (memcmp(slip_payload, link_control_sync, sizeof(link_control_sync)) == 0){
541                         log_info("link: received sync in ACTIVE STATE!");
542                         // TODO sync during active indicates peer reset -> full upper layer reset necessary
543                         break;
544                     }
545                     if (memcmp(slip_payload, link_control_sleep, sizeof(link_control_sleep)) == 0){
546                         if (btstack_uart_sleep_mode){
547                             log_info("link: received sleep message. Enabling UART Sleep.");
548                             btstack_uart->set_sleep(btstack_uart_sleep_mode);
549                         } else {
550                             log_info("link: received sleep message. UART Sleep not supported");
551                         }
552                         link_peer_asleep = 1;
553                         break;
554                     }
555                     if (memcmp(slip_payload, link_control_wakeup, sizeof(link_control_wakeup)) == 0){
556                         log_info("link: received wakupe message -> send woken");
557                         link_peer_asleep = 0;
558                         hci_transport_link_actions |= HCI_TRANSPORT_LINK_SEND_WOKEN;
559                         break;
560                     }
561                     if (memcmp(slip_payload, link_control_woken, sizeof(link_control_woken)) == 0){
562                         log_info("link: received woken message");
563                         link_peer_asleep = 0;
564                         // queued packet will be sent in hci_transport_link_run if needed
565                         break;
566                     }
567                     break;
568                 case HCI_EVENT_PACKET:
569                 case HCI_ACL_DATA_PACKET:
570                 case HCI_SCO_DATA_PACKET:
571                     // seems like peer is awake
572                     link_peer_asleep = 0;
573                     // forward packet to stack
574                     packet_handler(link_packet_type, slip_payload, link_payload_len);
575                     // reset inactvitiy timer
576                     hci_transport_inactivity_timer_set();
577                     break;
578             }
579 
580             break;
581         default:
582             break;
583     }
584 
585     hci_transport_link_run();
586 }
587 
588 // recommendet time until resend: 3 * time of largest packet
589 static uint16_t hci_transport_link_calc_resend_timeout(uint32_t baudrate){
590     uint32_t max_packet_size_in_bit = (HCI_PACKET_BUFFER_SIZE + 6) << 3;
591     uint32_t t_max_x3_ms = max_packet_size_in_bit * 3000 / baudrate;
592     log_info("resend timeout for %u baud: %u ms", baudrate, t_max_x3_ms);
593     return t_max_x3_ms;
594 }
595 
596 static void hci_transport_link_update_resend_timeout(uint32_t baudrate){
597     link_resend_timeout_ms = hci_transport_link_calc_resend_timeout(baudrate);
598 }
599 
600 /// H5 Interface
601 
602 static uint8_t hci_transport_link_read_byte;
603 
604 static void hci_transport_h5_read_next_byte(void){
605     log_debug("h5: rx nxt");
606     btstack_uart->receive_block(&hci_transport_link_read_byte, 1);
607 }
608 
609 static void hci_transport_h5_block_received(){
610     log_debug("slip: process 0x%02x", hci_transport_link_read_byte);
611     btstack_slip_decoder_process(hci_transport_link_read_byte);
612     uint16_t frame_size = btstack_slip_decoder_frame_size();
613     if (frame_size) {
614         hci_transport_h5_process_frame(frame_size);
615         hci_transport_slip_init();
616     }
617     hci_transport_h5_read_next_byte();
618 }
619 
620 static void hci_transport_h5_block_sent(void){
621 
622     // check if more data to send
623     if (btstack_slip_encoder_has_data()){
624         hci_transport_slip_send_next_chunk();
625         return;
626     }
627 
628     // done
629     slip_write_active = 0;
630 
631     // enter sleep mode after sending sleep message
632     if (hci_transport_link_actions & HCI_TRANSPORT_LINK_ENTER_SLEEP){
633         hci_transport_link_actions &= ~HCI_TRANSPORT_LINK_ENTER_SLEEP;
634         if (btstack_uart_sleep_mode){
635             log_info("link: sent sleep message. Enabling UART Sleep.");
636             btstack_uart->set_sleep(btstack_uart_sleep_mode);
637         } else {
638             log_info("link: sent sleep message. UART Sleep not supported");
639         }
640     }
641 
642     hci_transport_link_run();
643 }
644 
645 static void hci_transport_h5_init(const void * transport_config){
646     // check for hci_transport_config_uart_t
647     if (!transport_config) {
648         log_error("hci_transport_h5: no config!");
649         return;
650     }
651     if (((hci_transport_config_t*)transport_config)->type != HCI_TRANSPORT_CONFIG_UART) {
652         log_error("hci_transport_h5: config not of type != HCI_TRANSPORT_CONFIG_UART!");
653         return;
654     }
655 
656     // extract UART config from transport config
657     hci_transport_config_uart_t * hci_transport_config_uart = (hci_transport_config_uart_t*) transport_config;
658     uart_config.baudrate    = hci_transport_config_uart->baudrate_init;
659     uart_config.flowcontrol = hci_transport_config_uart->flowcontrol;
660     uart_config.device_name = hci_transport_config_uart->device_name;
661 
662     // setup UART driver
663     btstack_uart->init(&uart_config);
664     btstack_uart->set_block_received(&hci_transport_h5_block_received);
665     btstack_uart->set_block_sent(&hci_transport_h5_block_sent);
666 }
667 
668 static int hci_transport_h5_open(void){
669     int res = btstack_uart->open();
670     if (res){
671         return res;
672     }
673 
674     // check if wake on RX can be used
675     btstack_uart_sleep_mode = BTSTACK_UART_SLEEP_OFF;
676     int supported_sleep_modes = 0;
677     if (btstack_uart->get_supported_sleep_modes){
678         supported_sleep_modes = btstack_uart->get_supported_sleep_modes();
679     }
680     if (supported_sleep_modes & BTSTACK_UART_SLEEP_MASK_RTS_LOW_WAKE_ON_RX_EDGE){
681         log_info("H5: using wake on RX");
682         btstack_uart_sleep_mode = BTSTACK_UART_SLEEP_RTS_LOW_WAKE_ON_RX_EDGE;
683     } else {
684         log_info("H5: UART driver does not provide compatible sleep mode");
685     }
686 
687     // setup resend timeout
688     hci_transport_link_update_resend_timeout(uart_config.baudrate);
689 
690     // init slip parser state machine
691     hci_transport_slip_init();
692 
693     // init link management - already starts syncing
694     hci_transport_link_init();
695 
696     // start receiving
697     hci_transport_h5_read_next_byte();
698 
699     return 0;
700 }
701 
702 static int hci_transport_h5_close(void){
703     return btstack_uart->close();
704     return 0;
705 }
706 
707 static void hci_transport_h5_register_packet_handler(void (*handler)(uint8_t packet_type, uint8_t *packet, uint16_t size)){
708     packet_handler = handler;
709 }
710 
711 static int hci_transport_h5_can_send_packet_now(uint8_t packet_type){
712     int res = !hci_transport_link_have_outgoing_packet() && link_state == LINK_ACTIVE;
713     // log_info("hci_transport_h5_can_send_packet_now: %u", res);
714     return res;
715 }
716 
717 static int hci_transport_h5_send_packet(uint8_t packet_type, uint8_t *packet, int size){
718     if (!hci_transport_h5_can_send_packet_now(packet_type)){
719         log_error("hci_transport_h5_send_packet called but in state %u", link_state);
720         return -1;
721     }
722 
723     // store request
724     hci_transport_h5_queue_packet(packet_type, packet, size);
725 
726     // send wakeup first
727     if (link_peer_asleep){
728         if (btstack_uart_sleep_mode){
729             log_info("h5: disable UART sleep");
730             btstack_uart->set_sleep(BTSTACK_UART_SLEEP_OFF);
731         }
732         hci_transport_link_actions |= HCI_TRANSPORT_LINK_SEND_WAKEUP;
733         hci_transport_link_set_timer(LINK_WAKEUP_MS);
734     } else {
735         hci_transport_link_actions |= HCI_TRANSPORT_LINK_SEND_QUEUED_PACKET;
736         hci_transport_link_set_timer(link_resend_timeout_ms);
737     }
738     hci_transport_link_run();
739     return 0;
740 }
741 
742 static int hci_transport_h5_set_baudrate(uint32_t baudrate){
743 
744     log_info("hci_transport_h5_set_baudrate %u", baudrate);
745     int res = btstack_uart->set_baudrate(baudrate);
746 
747     if (res) return res;
748     hci_transport_link_update_resend_timeout(baudrate);
749     return 0;
750 }
751 
752 static void hci_transport_h5_reset_link(void){
753 
754     log_info("hci_transport_h5_reset_link");
755 
756     // clear outgoing queue
757     hci_transport_link_clear_queue();
758 
759     // init slip parser state machine
760     hci_transport_slip_init();
761 
762     // init link management - already starts syncing
763     hci_transport_link_init();
764 }
765 
766 static const hci_transport_t hci_transport_h5 = {
767     /* const char * name; */                                        "H5",
768     /* void   (*init) (const void *transport_config); */            &hci_transport_h5_init,
769     /* int    (*open)(void); */                                     &hci_transport_h5_open,
770     /* int    (*close)(void); */                                    &hci_transport_h5_close,
771     /* void   (*register_packet_handler)(void (*handler)(...); */   &hci_transport_h5_register_packet_handler,
772     /* int    (*can_send_packet_now)(uint8_t packet_type); */       &hci_transport_h5_can_send_packet_now,
773     /* int    (*send_packet)(...); */                               &hci_transport_h5_send_packet,
774     /* int    (*set_baudrate)(uint32_t baudrate); */                &hci_transport_h5_set_baudrate,
775     /* void   (*reset_link)(void); */                               &hci_transport_h5_reset_link,
776 };
777 
778 // configure and return h5 singleton
779 const hci_transport_t * hci_transport_h5_instance(const btstack_uart_block_t * uart_driver) {
780     btstack_uart = uart_driver;
781     return &hci_transport_h5;
782 }
783 
784 void hci_transport_h5_set_auto_sleep(uint16_t inactivity_timeout_ms){
785     link_inactivity_timeout_ms = inactivity_timeout_ms;
786 }
787