Merge branch 'master' of https://github.com/bluekitchen/btstack

README.md

@@ -5,8 +5,8 @@ It is well suited for small, resource-constraint devices
 such as 8 or 16 bit embedded systems as it is highly configurable and comes with an ultra small memory footprint. 
 A minimal configuration for an SPP server on a MSP430 can run in 32 kB FLASH and only 4 kB of RAM.
 
-It connects to the Bluetooth modules via different Bluetooth HCI transport layers (e.g., HCI H4 UART and 
+It connects to the Bluetooth modules via a different Bluetooth HCI transport layers (e.g., HCI H4 UART and 
-H5 the "Tree-Wire" protocol). The various platforms can be easily targeted by providing the necessary 
+H5 the "Tree-Wire" protocol, HCI H2 USB). Various platforms can be easily targeted by providing the necessary 
 UART, CPU, and CLOCK implementations. 
 
 On smaller embedded systems, a minimal run loop implementation allows to use BTstack without a Real Time OS (RTOS). 
@@ -15,17 +15,15 @@ If a RTOS is already provided, BTstack can be integrated and run as a single thr
 On larger systems, BTstack provides a daemon that connects to a Bluetooth module. 
 Multiple applications can communicate with this daemon over different inter-process communication methods.
 
-BTstack supports both, the Central and the Peripheral Role of Bluetooth 4.0 Low Energy specification. 
+BTstack supports both, the Central and the Peripheral Role of Bluetooth 4.2 Low Energy specification. 
 It can be configures as both a single mode or a dual mode stack.
 
 BTstack is free for non-commercial use. For commercial use, <a href="mailto:contact@bluekitchen-gmbh.com">tell us</a> 
 a bit about your project to get a quote.
-The Serial Port Profile (SPP) and the Bluetooth 4.0 Low Energy Peripheral role (LE Peripheral) have been qualified with 
+It has been qualified with the the Bluetooth SIG for GAP, IOP, HFP, HSP, SPP, PAN profiles and 
-the Bluetooth SIG (QD ID 54558). This summer, we plan to qualify for Bluetooth Core 4.2,
+GATT, SM of the Bluetooth 4.2 LE Central and Peripheral roles (QD ID 25340).
-together with LE Central, PAN/BNEP and HSP.
 
 ## Documentation
-For starters, check the BTstack Manual 
 - [HTML](http://bluekitchen-gmbh.com/btstack/)
 - [PDF](http://bluekitchen-gmbh.com/btstack.pdf)
 
@@ -41,11 +39,13 @@ For starters, check the BTstack Manual
 ## Supported Profiles
 * GAP              
 * IOP              
+* HFP
+* HSP
 * SPP              
 * PAN              
 * GATT             
 
-Coming soon: HSP, HFP, and more.
+Coming next: HID, HOGP, A2DP, and more.
 
 ## Evaluation Platforms
 
@@ -73,13 +73,13 @@ Status               | Platform
 ## Supported Chipsets
 Chipsets             | Status
 --------------       | ------ 
-TI CC256x, WL183x    | complete incl. eHCIll support (chipset-cc256x)
+TI CC256x, WL183x    | complete incl. eHCIll support and SCO-over-HCI (chipset-cc256x)
-CSR 8811, 8510       | H4 only (chipset-csr)
+CSR 8x10, 8x11       | H4 only (chipset-csr), SCO-over-HCI missing
 STM STLC2500D        | working, no support for custom deep sleep management (chipset-stlc2500d)
 TC35661              | working, BLE patches missing (chipset-tc3566x)
-EM 9301              | experimental use on Arduino Shield (chipset-em9301)
+EM 9301 (LE-only)    | working, used on Arduino Shield (chipset-em9301)
-CSR USB Dongles      | complete
+CSR USB Dongles      | complete, incl. SCO-over-HCI 
-Broadcom USB Dongles | complete
+Broadcom USB Dongles | complete, SCO-over-HCI not working
 
 ## Discussion and Community Support
 [BTstack Google Group](http://groups.google.com/group/btstack-dev)

ble/compile-gatt.py

@@ -441,6 +441,49 @@ def parseCharacteristicAggregateFormat(fout, parts):
     fout.write("\n")
     handle = handle + 1
 
+def parseReportReference(fout, parts):
+    global handle
+    global total_size
+
+    property_read = property_flags['READ'];
+    size = 2 + 2 + 2 + 2 + 1 + 1
+
+    report_id = parts[1]
+    report_type = parts[2]
+
+    write_indent(fout)
+    fout.write('// 0x%04x REPORT_REFERENCE-%s\n' % (handle, '-'.join(parts[1:])))
+    write_indent(fout)
+    write_16(fout, size)
+    write_16(fout, property_read)
+    write_16(fout, handle)
+    write_16(fout, 0x2908)
+    write_sequence(fout, report_id)
+    write_sequence(fout, report_type)
+    fout.write("\n")
+    handle = handle + 1
+
+
+def parseNumberOfDigitals(fout, parts):
+    global handle
+    global total_size
+
+    property_read = property_flags['READ'];
+    size = 2 + 2 + 2 + 2 + 1
+
+    no_of_digitals = parts[1]
+
+    write_indent(fout)
+    fout.write('// 0x%04x NUMBER_OF_DIGITALS-%s\n' % (handle, '-'.join(parts[1:])))
+    write_indent(fout)
+    write_16(fout, size)
+    write_16(fout, property_read)
+    write_16(fout, handle)
+    write_16(fout, 0x2909)
+    write_sequence(fout, no_of_digitals)
+    fout.write("\n")
+    handle = handle + 1
+
 
 def parse(fname_in, fin, fname_out, fout):
     global handle
@@ -478,26 +521,81 @@ def parse(fname_in, fin, fname_out, fout):
                 parseIncludeService(fout, parts)
                 continue
 
+            # 2803
             if parts[0] == 'CHARACTERISTIC':
                 parseCharacteristic(fout, parts)
                 continue
-            
+
+            # 2900 Characteristic Extended Properties
+
+            # 2901
             if parts[0] == 'CHARACTERISTIC_USER_DESCRIPTION':
                 parseCharacteristicUserDescription(fout, parts)
                 continue
 
+            # 2902 Client Characteristic Configuration - included in Characteristic if
+            # notification / indication is supported
+
+            # 2903
             if parts[0] == 'SERVER_CHARACTERISTIC_CONFIGURATION':
                 parseServerCharacteristicConfiguration(fout, parts)
                 continue
 
+            # 2904
             if parts[0] == 'CHARACTERISTIC_FORMAT':
                 parseCharacteristicFormat(fout, parts)
                 continue
 
+            # 2905
             if parts[0] == 'CHARACTERISTIC_AGGREGATE_FORMAT':
                 parseCharacteristicAggregateFormat(fout, parts)
                 continue
 
+            # 2906 
+            if parts[0] == 'VALID_RANGE':
+                print("WARNING: %s not implemented yet\n" % (parts[0]))
+                continue
+
+            # 2907 
+            if parts[0] == 'EXTERNAL_REPORT_REFERENCE':
+                print("WARNING: %s not implemented yet\n" % (parts[0]))
+                continue
+
+            # 2908
+            if parts[0] == 'REPORT_REFERENCE':
+                parseReportReference(fout, parts)
+                continue
+
+            # 2909
+            if parts[0] == 'NUMBER_OF_DIGITALS':
+                parseNumberOfDigitals(fout, parts)
+                continue
+
+            # 290A
+            if parts[0] == 'VALUE_TRIGGER_SETTING':
+                print("WARNING: %s not implemented yet\n" % (parts[0]))
+                continue
+
+            # 290B
+            if parts[0] == 'ENVIRONMENTAL_SENSING_CONFIGURATION':
+                print("WARNING: %s not implemented yet\n" % (parts[0]))
+                continue
+
+            # 290C
+            if parts[0] == 'ENVIRONMENTAL_SENSING_MEASUREMENT':
+                print("WARNING: %s not implemented yet\n" % (parts[0]))
+                continue
+
+            # 290D 
+            if parts[0] == 'ENVIRONMENTAL_SENSING_TRIGGER_SETTING':
+                print("WARNING: %s not implemented yet\n" % (parts[0]))
+                continue
+
+            # 2906 
+            if parts[0] == 'VALID_RANGE':
+                print("WARNING: %s not implemented yet\n" % (parts[0]))
+                continue
+
             print("WARNING: unknown token: %s\n" % (parts[0]))
 
     write_indent(fout)

example/embedded/hsp_hs_test.c

@@ -43,12 +43,19 @@
 //
 // Tested working setups: 
 // - Ubuntu 14 64-bit, CC2564B connected via FTDI USB-2-UART adapter, 921600 baud
-//
+// - Ubuntu 14 64-bit, CSR dongle
-// Non working setups:
+// - OS X 10.11, CSR dongle
+
+// Broken setups:
 // - OS X 10.11, CC2564B connected via FDTI USB-2-UART adapter, 921600 baud
 //   - select(..) blocks > 400 ms -> num completed is received to late -> gaps between audio
 //   - looks like bug in select->FTDI driver as it works correct on Linux
-// - OS X 10.11, USB Bluetooth Dongles...
+// 
+// SCO not routed over HCI (yet)
+// - CSR UART dongle 
+// - Broadcom USB dongle
+// - Broadcom UART chipset
+// - ..
 // *****************************************************************************
 
 #include "btstack-config.h"
@@ -115,20 +122,24 @@ static void try_send_sco(void){
         // printf("try_send_sco, cannot send now\n");
         return;
     }
-    const int frames_per_packet = 180;
+
+    const int sco_packet_length = hci_get_sco_packet_length();
+    const int sco_payload_length = sco_packet_length - 3;
+    const int frames_per_packet = sco_payload_length;    // for 8-bit data. for 16-bit data it's /2
+
     hci_reserve_packet_buffer();
     uint8_t * sco_packet = hci_get_outgoing_packet_buffer();
     // set handle + flags
     bt_store_16(sco_packet, 0, sco_handle);
     // set len
-    sco_packet[2] = frames_per_packet;
+    sco_packet[2] = sco_payload_length;
     int i;
     for (i=0;i<frames_per_packet;i++){
         sco_packet[3+i] = sine[phase];
         phase++;
         if (phase >= sizeof(sine)) phase = 0;
     }
-    hci_send_sco_packet_buffer(3 + frames_per_packet);
+    hci_send_sco_packet_buffer(sco_packet_length);
     static int count = 0;
     count++;
     if ((count & 15) == 0) printf("Sent %u\n", count);
@@ -216,6 +227,10 @@ int btstack_main(int argc, const char * argv[]){
     compute_signal();
 #endif
 
+    // 8-bit, 2's complement (== int8_t)
+    // 16-bit samples probably required for USB: 
+    // hci_set_sco_voice_setting(0x0060);
+
     hci_register_sco_packet_handler(&sco_packet_handler);
 
     hci_discoverable_control(1);

platforms/libusb/btstack-config.h

@@ -21,6 +21,7 @@
 #define HAVE_HCI_DUMP
 #define SDP_DES_DUMP
 
-// #define HAVE_SCO
+#define HAVE_SCO
+#define HAVE_SCO_OVER_HCI
 
 #endif

platforms/posix/src/hci_transport_h2_libusb.c

@@ -65,16 +65,44 @@
 #include "hci.h"
 #include "hci_transport.h"
 
-// #define HAVE_SCO
-
 #if (USB_VENDOR_ID != 0) && (USB_PRODUCT_ID != 0)
 #define HAVE_USB_VENDOR_ID_AND_PRODUCT_ID
 #endif
 
+#define ASYNC_BUFFERS 2
+#define AYSNC_POLLING_INTERVAL_MS 1
+
+//
+// Bluetooth USB Transprot Alternate Settings:
+//
+// 0: No active voice channels (for USB compliance)
+// 1: One 8 kHz voice channel with 8-bit encoding
+// 2: Two 8 kHz voice channels with 8-bit encoding or one 8 kHz voice channel with 16-bit encoding
+// 3: Three 8 kHz voice channels with 8-bit encoding
+// 4: Two 8 kHz voice channels with 16-bit encoding or one 16 kHz voice channel with 16-bit encoding
+// 5: Three 8 kHz voice channels with 16-bit encoding or one 8 kHz voice channel with 16-bit encoding and one 16 kHz voice channel with 16-bit encoding
+// --> support only a single SCO connection
+#define ALT_SETTING (2)
+
+// for ALT_SETTING >= 1 and 8-bit channel, we need the following isochronous packets
+// One complete SCO packet with 24 frames every 3 frames (== 3 ms)
+#define NUM_ISO_PACKETS (3)
+// results in 9 bytes per frame
+#define ISO_PACKET_SIZE (9)
+
+// 49 bytes is the max usb packet size for alternate setting 5 (Three 8 kHz 16-bit channels or one 8 kHz 16-bit channel and one 16 kHz 16-bit channel)
+// note: alt setting 6 has max packet size of 63 every 7.5 ms = 472.5 bytes / HCI packet, while max SCO packet has 255 byte payload
+#define SCO_PACKET_SIZE  (49)
+
+// Outgoing SCO packet queue
+// simplified ring buffer implementation
+#define SCO_RING_BUFFER_COUNT  (8)
+#define SCO_RING_BUFFER_SIZE (SCO_RING_BUFFER_COUNT * SCO_PACKET_SIZE)
+
 // prototypes
 static void dummy_handler(uint8_t packet_type, uint8_t *packet, uint16_t size); 
-static int usb_close(void *transport_config);
+static int usb_close(void *transport_config);    
-    
+
 typedef enum {
     LIB_USB_CLOSED = 0,
     LIB_USB_OPENED,
@@ -103,28 +131,32 @@ static libusb_device        * dev;
 #endif
 static libusb_device_handle * handle;
 
-#define ASYNC_BUFFERS 2
-#define AYSNC_POLLING_INTERVAL_MS 1
-#define NUM_ISO_PACKETS 16
-#define SCO_PACKET_SIZE 49
-
 static struct libusb_transfer *command_out_transfer;
 static struct libusb_transfer *acl_out_transfer;
 static struct libusb_transfer *event_in_transfer[ASYNC_BUFFERS];
 static struct libusb_transfer *acl_in_transfer[ASYNC_BUFFERS];
 
+#ifdef HAVE_SCO
+
+// incoming SCO
 static H2_SCO_STATE sco_state;
 static uint8_t  sco_buffer[255+3 + SCO_PACKET_SIZE];
 static uint16_t sco_read_pos;
 static uint16_t sco_bytes_to_read;
-
-#ifdef HAVE_SCO
-static struct  libusb_transfer *sco_out_transfer;
 static struct  libusb_transfer *sco_in_transfer[ASYNC_BUFFERS];
-static uint8_t hci_sco_in_buffer[ASYNC_BUFFERS][NUM_ISO_PACKETS * SCO_PACKET_SIZE]; 
+static uint8_t hci_sco_in_buffer[ASYNC_BUFFERS][SCO_PACKET_SIZE]; 
+
+// outgoing SCO
+static uint8_t  sco_ring_buffer[SCO_RING_BUFFER_SIZE];
+static int      sco_ring_write;  // packet idx
+static int      sco_ring_transfers_active;
+static struct libusb_transfer *sco_ring_transfers[SCO_RING_BUFFER_COUNT];
 #endif
 
+// outgoing buffer for HCI Command packets
 static uint8_t hci_cmd_buffer[3 + 256 + LIBUSB_CONTROL_SETUP_SIZE];
+
+// incoming buffer for HCI Events and ACL Packets
 static uint8_t hci_event_in_buffer[ASYNC_BUFFERS][HCI_ACL_BUFFER_SIZE]; // bigger than largest packet
 static uint8_t hci_acl_in_buffer[ASYNC_BUFFERS][HCI_INCOMING_PRE_BUFFER_SIZE + HCI_ACL_BUFFER_SIZE]; 
 
@@ -138,7 +170,6 @@ static timer_source_t usb_timer;
 static int usb_timer_active;
 
 static int usb_acl_out_active = 0;
-static int usb_sco_out_active = 0;
 static int usb_command_active = 0;
 
 // endpoint addresses
@@ -149,6 +180,17 @@ static int sco_in_addr;
 static int sco_out_addr;
 
 
+static void sco_ring_init(void){
+    sco_ring_write = 0;
+    sco_ring_transfers_active = 0;
+}
+
+static int sco_ring_have_space(void){
+    return sco_ring_transfers_active < SCO_RING_BUFFER_COUNT;
+}
+
+
+//
 static void queue_transfer(struct libusb_transfer *transfer){
 
     // log_info("queue_transfer %p, endpoint %x size %u", transfer, transfer->endpoint, transfer->actual_length);
@@ -198,6 +240,48 @@ static void async_callback(struct libusb_transfer *transfer)
     // log_info("end async_callback");
 }
 
+
+static int usb_send_sco_packet(uint8_t *packet, int size){
+#ifdef HAVE_SCO
+    int r;
+
+    if (libusb_state != LIB_USB_TRANSFERS_ALLOCATED) return -1;
+
+    // log_info("usb_send_acl_packet enter, size %u", size);
+
+    // store packet in free slot
+    int tranfer_index = sco_ring_write;
+    uint8_t * data = &sco_ring_buffer[tranfer_index * SCO_PACKET_SIZE];
+    memcpy(data, packet, size);
+
+    // setup transfer
+    struct libusb_transfer * sco_transfer = sco_ring_transfers[tranfer_index];
+    libusb_fill_iso_transfer(sco_transfer, handle, sco_out_addr, data, size, NUM_ISO_PACKETS, async_callback, NULL, 0);
+    libusb_set_iso_packet_lengths(sco_transfer, ISO_PACKET_SIZE);
+    r = libusb_submit_transfer(sco_transfer);
+    if (r < 0) {
+        log_error("Error submitting sco transfer, %d", r);
+        return -1;
+    }
+
+    // mark slot as full
+    sco_ring_write++;
+    if (sco_ring_write == SCO_RING_BUFFER_COUNT){
+        sco_ring_write = 0;
+    }
+    sco_ring_transfers_active++;
+
+    // log_info("H2: queued packet at index %u, num active %u", tranfer_index, sco_ring_transfers_active);
+
+    // notify upper stack that packet processed and that it might be possible to send again
+    if (sco_ring_have_space()){
+        uint8_t event[] = { DAEMON_EVENT_HCI_PACKET_SENT, 0};
+        packet_handler(HCI_EVENT_PACKET, &event[0], sizeof(event));
+    } 
+#endif
+    return 0;
+}
+
 static void sco_state_machine_init(void){
     sco_state = H2_W4_SCO_HEADER;
     sco_read_pos = 0;
@@ -247,7 +331,7 @@ static void handle_completed_transfer(struct libusb_transfer *transfer){
         packet_handler(HCI_ACL_DATA_PACKET, transfer-> buffer, transfer->actual_length);
         resubmit = 1;
     } else if (transfer->endpoint == sco_in_addr) {
-        // log_info("handle_completed_transfer for SCO IN! num packets %u", transfer->num_iso_packets);
+        // log_info("handle_completed_transfer for SCO IN! num packets %u", transfer->NUM_ISO_PACKETS);
         int i;
         for (i = 0; i < transfer->num_iso_packets; i++) {
             struct libusb_iso_packet_descriptor *pack = &transfer->iso_packet_desc[i];
@@ -258,7 +342,7 @@ static void handle_completed_transfer(struct libusb_transfer *transfer){
             if (!pack->actual_length) continue;
             uint8_t * data = libusb_get_iso_packet_buffer_simple(transfer, i);
             // printf_hexdump(data, pack->actual_length);
-            // log_debug("handle_isochronous_data,size %u/%u", pack->length, pack->actual_length);
+            // log_info("handle_isochronous_data,size %u/%u", pack->length, pack->actual_length);
             handle_isochronous_data(data, pack->actual_length);
         }
         resubmit = 1;
@@ -271,10 +355,17 @@ static void handle_completed_transfer(struct libusb_transfer *transfer){
         usb_acl_out_active = 0;
         signal_done = 1;
     } else if (transfer->endpoint == sco_out_addr){
-        log_info("sco out done, size %u/%u - status %x", transfer->actual_length, 
+        log_info("sco out done, {{ %u/%u (%x)}, { %u/%u (%x)}, { %u/%u (%x)}}", 
-            transfer->iso_packet_desc[0].actual_length, transfer->iso_packet_desc[0].status);
+            transfer->iso_packet_desc[0].actual_length, transfer->iso_packet_desc[0].length, transfer->iso_packet_desc[0].status,
-        usb_sco_out_active = 0;
+            transfer->iso_packet_desc[1].actual_length, transfer->iso_packet_desc[1].length, transfer->iso_packet_desc[1].status,
-        signal_done = 1;
+            transfer->iso_packet_desc[2].actual_length, transfer->iso_packet_desc[2].length, transfer->iso_packet_desc[2].status);
+        if (!sco_ring_have_space()) {
+            // if there isn't space, the last SCO send didn't emit a packet sent event
+            signal_done = 1;
+        }
+        // decrease tab
+        sco_ring_transfers_active--;
+        // log_info("H2: sco out complete, num active num active %u", sco_ring_transfers_active);
     } else {
         log_info("usb_process_ds endpoint unknown %x", transfer->endpoint);
     }
@@ -527,9 +618,10 @@ static int prepare_device(libusb_device_handle * aHandle){
         libusb_close(aHandle);
         return r;
     }
-    r = libusb_set_interface_alt_setting(aHandle, 1, 5); // 3 x 8 kHz voice channels
+    log_info("Switching to setting %u on interface 1..", ALT_SETTING);
+    r = libusb_set_interface_alt_setting(aHandle, 1, ALT_SETTING); 
     if (r < 0) {
-        fprintf(stderr, "Error setting alternative setting 5 for interface 1: %s\n", libusb_error_name(r));
+        fprintf(stderr, "Error setting alternative setting %u for interface 1: %s\n", ALT_SETTING, libusb_error_name(r));
         libusb_close(aHandle);
         return r;
     }
@@ -542,6 +634,7 @@ static int usb_open(void *transport_config){
     int r;
 
     sco_state_machine_init();
+    sco_ring_init();
     handle_packet = NULL;
 
     // default endpoint addresses
@@ -666,6 +759,7 @@ static int usb_open(void *transport_config){
 
 #ifdef HAVE_SCO
 
+    // incoming
     for (c = 0 ; c < ASYNC_BUFFERS ; c++) {
         sco_in_transfer[c] = libusb_alloc_transfer(NUM_ISO_PACKETS); // isochronous transfers SCO in
         log_info("Alloc iso transfer");
@@ -673,14 +767,10 @@ static int usb_open(void *transport_config){
             usb_close(handle);
             return LIBUSB_ERROR_NO_MEM;
         }
-       // configure sco_in handlers
+        // configure sco_in handlers
         libusb_fill_iso_transfer(sco_in_transfer[c], handle, sco_in_addr, 
-                hci_sco_in_buffer[c], NUM_ISO_PACKETS * SCO_PACKET_SIZE, NUM_ISO_PACKETS, async_callback, NULL, 0) ;
+            hci_sco_in_buffer[c], SCO_PACKET_SIZE, NUM_ISO_PACKETS, async_callback, NULL, 0);
-        libusb_set_iso_packet_lengths(sco_in_transfer[c], SCO_PACKET_SIZE);
+        libusb_set_iso_packet_lengths(sco_in_transfer[c], ISO_PACKET_SIZE);
-        // one of the following is relevant! find out which one
-        sco_in_transfer[c]->type = LIBUSB_TRANSFER_TYPE_ISOCHRONOUS;
-        sco_in_transfer[c]->num_iso_packets = NUM_ISO_PACKETS;
-        // sco_in_transfer[c]->iso_packet_desc[0].length = 300;
         r = libusb_submit_transfer(sco_in_transfer[c]);
         log_info("Submit iso transfer res = %d", r);
         if (r) {
@@ -689,7 +779,11 @@ static int usb_open(void *transport_config){
             return r;
         }
     }
-    sco_out_transfer = libusb_alloc_transfer(1); // 1 isochronous transfers SCO out
+
+    // outgoing
+    for (c=0; c < SCO_RING_BUFFER_COUNT ; c++){
+        sco_ring_transfers[c] = libusb_alloc_transfer(NUM_ISO_PACKETS); // 1 isochronous transfers SCO out - up to 3 parts
+    }
 #endif
 
     for (c = 0 ; c < ASYNC_BUFFERS ; c++) {
@@ -876,35 +970,6 @@ static int usb_send_acl_packet(uint8_t *packet, int size){
     return 0;
 }
 
-static int usb_send_sco_packet(uint8_t *packet, int size){
-#ifdef HAVE_SCO
-    int r;
-
-    if (libusb_state != LIB_USB_TRANSFERS_ALLOCATED) return -1;
-
-    // log_info("usb_send_acl_packet enter, size %u", size);
-    
-    // prepare transfer
-    int completed = 0;
-    libusb_fill_iso_transfer(sco_out_transfer, handle, sco_out_addr, packet, size, 1,
-        async_callback, &completed, 0);
-    libusb_set_iso_packet_lengths(sco_out_transfer, size);
-    sco_out_transfer->type = LIBUSB_TRANSFER_TYPE_ISOCHRONOUS;
-    sco_out_transfer->iso_packet_desc[0].length = size;
-
-    // update state before submitting transfer
-    usb_sco_out_active = 1;
-
-    r = libusb_submit_transfer(sco_out_transfer);
-    if (r < 0) {
-        usb_sco_out_active = 0;
-        log_error("Error submitting sco transfer, %d", r);
-        return -1;
-    }
-#endif
-    return 0;
-}
-
 static int usb_can_send_packet_now(uint8_t packet_type){
     switch (packet_type){
         case HCI_COMMAND_DATA_PACKET:
@@ -912,7 +977,7 @@ static int usb_can_send_packet_now(uint8_t packet_type){
         case HCI_ACL_DATA_PACKET:
             return !usb_acl_out_active;
         case HCI_SCO_DATA_PACKET:
-            return !usb_sco_out_active;
+            return sco_ring_have_space();
         default:
             return 0;
     }

src/hci.c

@@ -3458,6 +3458,16 @@ uint16_t hci_get_sco_voice_setting(){
     return hci_stack->sco_voice_setting;
 }
 
+/** @brief Get SCO packet length for current SCO Voice setting
+ *  @note  Using SCO packets of the exact length is required for USB transfer
+ *  @return Length of SCO packets in bytes (not audio frames)
+ */
+int hci_get_sco_packet_length(void){
+    // see Core Spec for H2 USB Transfer. 
+    if (hci_stack->sco_voice_setting & 0x0020) return 51;
+    return 27;
+}
+
 /**
  * @brief Set callback for Bluetooth Hardware Error
  */

src/hci.h

@@ -970,6 +970,12 @@ void hci_set_sco_voice_setting(uint16_t voice_setting);
  */
 uint16_t hci_get_sco_voice_setting(void);
 
+/** @brief Get SCO packet length for current SCO Voice setting
+ *  @note  Using SCO packets of the exact length is required for USB transfer
+ *  @return Length of SCO packets in bytes (not audio frames) incl. 3 byte header
+ */
+int hci_get_sco_packet_length(void);
+
 /* API_END */
 
 /**