Mike R
USB device stack, with KL25Z fixes for USB 3.0 hosts and sleep/resume interrupt handling
Dependents: frdm_Slider_Keyboard idd_hw2_figlax_PanType idd_hw2_appachu_finger_chording idd_hw3_AngieWangAntonioDeLimaFernandesDanielLim_BladeSymphony ... more
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USBDevice
by 
mbed official
This is an overhauled version of the standard mbed USB device-side driver library, with bug fixes for KL25Z devices. It greatly improves reliability and stability of USB on the KL25Z, especially with devices using multiple endpoints concurrently.
I've had some nagging problems with the base mbed implementation for a long time, manifesting as occasional random disconnects that required rebooting the device. Recently (late 2015), I started implementing a USB device on the KL25Z that used multiple endpoints, and suddenly the nagging, occasional problems turned into frequent and predictable crashes. This forced me to delve into the USB stack and figure out what was really going on. Happily, the frequent crashes made it possible to track down and fix the problems. This new version is working very reliably in my testing - the random disconnects seem completely eradicated, even under very stressful conditions for the device.
Summary
- Overall stability improvements
- USB 3.0 host support
- Stalled endpoint fixes
- Sleep/resume notifications
- Smaller memory footprint
- General code cleanup
Update - 2/15/2016
My recent fixes introduced a new problem that made the initial connection fail most of the time on certain hosts. It's not clear if the common thread was a particular type of motherboard or USB chip set, or a specific version of Windows, or what, but several people ran into it. We tracked the problem down to the "stall" fixes in the earlier updates, which we now know weren't quite the right fixes after all. The latest update (2/15/2016) fixes this. It has new and improved "unstall" handling that so far works well with diverse hosts.
Race conditions and overall stability
The base mbed KL25Z implementation has a lot of problems with "race conditions" - timing problems that can happen when hardware interrupts occur at inopportune moments. The library shares a bunch of static variable data between interrupt handler context and regular application context. This isn't automatically a bad thing, but it does require careful coordination to make sure that the interrupt handler doesn't corrupt data that the other code was in the middle of updating when an interrupt occurs. The base mbed code, though, doesn't do any of the necessary coordination. This makes it kind of amazing that the base code worked at all for anyone, but I guess the interrupt rate is low enough in most applications that the glitch rate was below anyone's threshold to seriously investigate.
This overhaul adds the necessary coordination for the interrupt handlers to protect against these data corruptions. I think it's very solid now, and hopefully entirely free of the numerous race conditions in the old code. It's always hard to be certain that you've fixed every possible bug like this because they strike (effectively) at random, but I'm pretty confident: my test application was reliably able to trigger glitches in the base code in a matter of minutes, but the same application (with the overhauled library) now runs for days on end without dropping the connection.
Stalled endpoint fixes
USB has a standard way of handling communications errors called a "stall", which basically puts the connection into an error mode to let both sides know that they need to reset their internal states and sync up again. The original mbed version of the USB device library doesn't seem to have the necessary code to recover from this condition properly. The KL25Z hardware does some of the work, but it also seems to require the software to take some steps to "un-stall" the connection. (I keep saying "seems to" because the hardware reference material is very sketchy about all of this. Most of what I've figured out is from observing the device in action with a Windows host.) This new version adds code to do the necessary re-syncing and get the connection going again, automatically, and transparently to the user.
USB 3.0 Hosts
The original mbed code sometimes didn't work when connecting to hosts with USB 3.0 ports. This didn't affect every host, but it affected many of them. The common element seemed to be the Intel Haswell chip set on the host, but there may be other chip sets affected as well. In any case, the problem affected many PCs from the Windows 7 and 8 generation, as well as many Macs. It was possible to work around the problem by avoiding USB 3.0 ports - you could use a USB 2 port on the host, or plug a USB 2 hub between the host and device. But I wanted to just fix the problem and eliminate the need for such workarounds. This modified version of the library has such a fix, which so far has worked for everyone who's tried.
Sleep/resume notifications
This modified version also contains an innocuous change to the KL25Z USB HAL code to handle sleep and resume interrupts with calls to suspendStateChanged(). The original KL25Z code omitted these calls (and in fact didn't even enable the interrupts), but I think this was an unintentional oversight - the notifier function is part of the generic API, and other supported boards all implement it. I use this feature in my own application so that I can distinguish sleep mode from actual disconnects and handle the two conditions correctly.
Smaller memory footprint
The base mbed version of the code allocates twice as much memory for USB buffers as it really needed to. It looks like the original developers intended to implement the KL25Z USB hardware's built-in double-buffering mechanism, but they ultimately abandoned that effort. But they left in the double memory allocation. This version removes that and allocates only what's actually needed. The USB buffers aren't that big (128 bytes per endpoint), so this doesn't save a ton of memory, but even a little memory is pretty precious on this machine given that it only has 16K.
(I did look into adding the double-buffering support that the original developers abandoned, but after some experimentation I decided they were right to skip it. It just doesn't seem to mesh well with the design of the rest of the mbed USB code. I think it would take a major rewrite to make it work, and it doesn't seem worth the effort given that most applications don't need it - it would only benefit applications that are moving so much data through USB that they're pushing the limits of the CPU. And even for those, I think it would be a lot simpler to build a purely software-based buffer rotation mechanism.)
General code cleanup
The KL25Z HAL code in this version has greatly expanded commentary and a lot of general cleanup. Some of the hardware constants were given the wrong symbolic names (e.g., EVEN and ODD were reversed), and many were just missing (written as hard-coded numbers without explanation). I fixed the misnomers and added symbolic names for formerly anonymous numbers. Hopefully the next person who has to overhaul this code will at least have an easier time understanding what I thought I was doing!
USBAudio/USBAudio.cpp
- Committer:
- mjr
- Date:
- 2017-03-17
- Revision:
- 54:2e181d51495a
- Parent:
- 49:03527ce6840e
File content as of revision 54:2e181d51495a:
/* Copyright (c) 2010-2011 mbed.org, MIT License
*
* Permission is hereby granted, free of charge, to any person obtaining a copy of this software
* and associated documentation files (the "Software"), to deal in the Software without
* restriction, including without limitation the rights to use, copy, modify, merge, publish,
* distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all copies or
* substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING
* BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
* DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/
#include "stdint.h"
#include "USBAudio.h"
#include "USBAudio_Types.h"
USBAudio::USBAudio(uint32_t frequency_in, uint8_t channel_nb_in, uint32_t frequency_out, uint8_t channel_nb_out, uint16_t vendor_id, uint16_t product_id, uint16_t product_release): USBDevice(vendor_id, product_id, product_release) {
mute = 0;
volCur = 0x0080;
volMin = 0x0000;
volMax = 0x0100;
volRes = 0x0004;
available = false;
FREQ_IN = frequency_in;
FREQ_OUT = frequency_out;
this->channel_nb_in = channel_nb_in;
this->channel_nb_out = channel_nb_out;
// stereo -> *2, mono -> *1
PACKET_SIZE_ISO_IN = (FREQ_IN / 500) * channel_nb_in;
PACKET_SIZE_ISO_OUT = (FREQ_OUT / 500) * channel_nb_out;
// STEREO -> left and right
channel_config_in = (channel_nb_in == 1) ? CHANNEL_M : CHANNEL_L + CHANNEL_R;
channel_config_out = (channel_nb_out == 1) ? CHANNEL_M : CHANNEL_L + CHANNEL_R;
SOF_handler = false;
buf_stream_out = NULL;
buf_stream_in = NULL;
interruptOUT = false;
writeIN = false;
interruptIN = false;
available = false;
volume = 0;
// connect the device
USBDevice::connect();
}
bool USBAudio::read(uint8_t * buf) {
buf_stream_in = buf;
SOF_handler = false;
while (!available || !SOF_handler);
available = false;
return true;
}
bool USBAudio::readNB(uint8_t * buf) {
buf_stream_in = buf;
SOF_handler = false;
while (!SOF_handler);
if (available) {
available = false;
buf_stream_in = NULL;
return true;
}
return false;
}
bool USBAudio::readWrite(uint8_t * buf_read, uint8_t * buf_write) {
buf_stream_in = buf_read;
SOF_handler = false;
writeIN = false;
if (interruptIN) {
USBDevice::writeNB(EP3IN, buf_write, PACKET_SIZE_ISO_OUT, PACKET_SIZE_ISO_OUT);
} else {
buf_stream_out = buf_write;
}
while (!available);
if (interruptIN) {
while (!writeIN);
}
while (!SOF_handler);
return true;
}
bool USBAudio::write(uint8_t * buf) {
writeIN = false;
SOF_handler = false;
if (interruptIN) {
USBDevice::writeNB(EP3IN, buf, PACKET_SIZE_ISO_OUT, PACKET_SIZE_ISO_OUT);
} else {
buf_stream_out = buf;
}
while (!SOF_handler);
if (interruptIN) {
while (!writeIN);
}
return true;
}
float USBAudio::getVolume() {
return (mute) ? 0.0 : volume;
}
bool USBAudio::EP3_OUT_callback() {
uint32_t size = 0;
interruptOUT = true;
if (buf_stream_in != NULL) {
readEP(EP3OUT, (uint8_t *)buf_stream_in, &size, PACKET_SIZE_ISO_IN);
available = true;
buf_stream_in = NULL;
}
readStart(EP3OUT, PACKET_SIZE_ISO_IN);
return false;
}
bool USBAudio::EP3_IN_callback() {
interruptIN = true;
writeIN = true;
return true;
}
// Called in ISR context on each start of frame
void USBAudio::SOF(int frameNumber) {
uint32_t size = 0;
if (!interruptOUT) {
// read the isochronous endpoint
if (buf_stream_in != NULL) {
if (USBDevice::readEP_NB(EP3OUT, (uint8_t *)buf_stream_in, &size, PACKET_SIZE_ISO_IN)) {
if (size) {
available = true;
readStart(EP3OUT, PACKET_SIZE_ISO_IN);
buf_stream_in = NULL;
}
}
}
}
if (!interruptIN) {
// write if needed
if (buf_stream_out != NULL) {
USBDevice::writeNB(EP3IN, (uint8_t *)buf_stream_out, PACKET_SIZE_ISO_OUT, PACKET_SIZE_ISO_OUT);
buf_stream_out = NULL;
}
}
SOF_handler = true;
}
// Called in ISR context
// Set configuration. Return false if the configuration is not supported.
bool USBAudio::USBCallback_setConfiguration(uint8_t configuration) {
if (configuration != DEFAULT_CONFIGURATION) {
return false;
}
// Configure isochronous endpoint
realiseEndpoint(EP3OUT, PACKET_SIZE_ISO_IN, ISOCHRONOUS);
realiseEndpoint(EP3IN, PACKET_SIZE_ISO_OUT, ISOCHRONOUS);
// activate readings on this endpoint
readStart(EP3OUT, PACKET_SIZE_ISO_IN);
return true;
}
// Called in ISR context
// Set alternate setting. Return false if the alternate setting is not supported
bool USBAudio::USBCallback_setInterface(uint16_t interface, uint8_t alternate) {
if (interface == 0 && alternate == 0) {
return true;
}
if (interface == 1 && (alternate == 0 || alternate == 1)) {
return true;
}
if (interface == 2 && (alternate == 0 || alternate == 1)) {
return true;
}
return false;
}
// Called in ISR context
// Called by USBDevice on Endpoint0 request
// This is used to handle extensions to standard requests and class specific requests.
// Return true if class handles this request
bool USBAudio::USBCallback_request() {
bool success = false;
CONTROL_TRANSFER * transfer = getTransferPtr();
// Process class-specific requests
if (transfer->setup.bmRequestType.Type == CLASS_TYPE) {
// Feature Unit: Interface = 0, ID = 2
if (transfer->setup.wIndex == 0x0200) {
// Master Channel
if ((transfer->setup.wValue & 0xff) == 0) {
switch (transfer->setup.wValue >> 8) {
case MUTE_CONTROL:
switch (transfer->setup.bRequest) {
case REQUEST_GET_CUR:
transfer->remaining = 1;
transfer->ptr = &mute;
transfer->direction = DEVICE_TO_HOST;
success = true;
break;
case REQUEST_SET_CUR:
transfer->remaining = 1;
transfer->notify = true;
transfer->direction = HOST_TO_DEVICE;
success = true;
break;
default:
break;
}
break;
case VOLUME_CONTROL:
switch (transfer->setup.bRequest) {
case REQUEST_GET_CUR:
transfer->remaining = 2;
transfer->ptr = (uint8_t *)&volCur;
transfer->direction = DEVICE_TO_HOST;
success = true;
break;
case REQUEST_GET_MIN:
transfer->remaining = 2;
transfer->ptr = (uint8_t *)&volMin;
transfer->direction = DEVICE_TO_HOST;
success = true;
break;
case REQUEST_GET_MAX:
transfer->remaining = 2;
transfer->ptr = (uint8_t *)&volMax;
transfer->direction = DEVICE_TO_HOST;
success = true;
break;
case REQUEST_GET_RES:
transfer->remaining = 2;
transfer->ptr = (uint8_t *)&volRes;
transfer->direction = DEVICE_TO_HOST;
success = true;
break;
case REQUEST_SET_CUR:
transfer->remaining = 2;
transfer->notify = true;
transfer->direction = HOST_TO_DEVICE;
success = true;
break;
case REQUEST_SET_MIN:
transfer->remaining = 2;
transfer->notify = true;
transfer->direction = HOST_TO_DEVICE;
success = true;
break;
case REQUEST_SET_MAX:
transfer->remaining = 2;
transfer->notify = true;
transfer->direction = HOST_TO_DEVICE;
success = true;
break;
case REQUEST_SET_RES:
transfer->remaining = 2;
transfer->notify = true;
transfer->direction = HOST_TO_DEVICE;
success = true;
break;
}
break;
default:
break;
}
}
}
}
return success;
}
// Called in ISR context when a data OUT stage has been performed
void USBAudio::USBCallback_requestCompleted(uint8_t * buf, uint32_t length) {
if ((length == 1) || (length == 2)) {
uint16_t data = (length == 1) ? *buf : *((uint16_t *)buf);
CONTROL_TRANSFER * transfer = getTransferPtr();
switch (transfer->setup.wValue >> 8) {
case MUTE_CONTROL:
switch (transfer->setup.bRequest) {
case REQUEST_SET_CUR:
mute = data & 0xff;
updateVol.call();
break;
default:
break;
}
break;
case VOLUME_CONTROL:
switch (transfer->setup.bRequest) {
case REQUEST_SET_CUR:
volCur = data;
volume = (float)volCur/(float)volMax;
updateVol.call();
break;
default:
break;
}
break;
default:
break;
}
}
}
#define TOTAL_DESCRIPTOR_LENGTH ((1 * CONFIGURATION_DESCRIPTOR_LENGTH) \
+ (5 * INTERFACE_DESCRIPTOR_LENGTH) \
+ (1 * CONTROL_INTERFACE_DESCRIPTOR_LENGTH + 1) \
+ (2 * INPUT_TERMINAL_DESCRIPTOR_LENGTH) \
+ (1 * FEATURE_UNIT_DESCRIPTOR_LENGTH) \
+ (2 * OUTPUT_TERMINAL_DESCRIPTOR_LENGTH) \
+ (2 * STREAMING_INTERFACE_DESCRIPTOR_LENGTH) \
+ (2 * FORMAT_TYPE_I_DESCRIPTOR_LENGTH) \
+ (2 * (ENDPOINT_DESCRIPTOR_LENGTH + 2)) \
+ (2 * STREAMING_ENDPOINT_DESCRIPTOR_LENGTH) )
#define TOTAL_CONTROL_INTF_LENGTH (CONTROL_INTERFACE_DESCRIPTOR_LENGTH + 1 + \
2*INPUT_TERMINAL_DESCRIPTOR_LENGTH + \
FEATURE_UNIT_DESCRIPTOR_LENGTH + \
2*OUTPUT_TERMINAL_DESCRIPTOR_LENGTH)
const uint8_t *USBAudio::configurationDesc() {
static const uint8_t configDescriptor[] = {
// Configuration 1
CONFIGURATION_DESCRIPTOR_LENGTH, // bLength
CONFIGURATION_DESCRIPTOR, // bDescriptorType
LSB(TOTAL_DESCRIPTOR_LENGTH), // wTotalLength (LSB)
MSB(TOTAL_DESCRIPTOR_LENGTH), // wTotalLength (MSB)
0x03, // bNumInterfaces
DEFAULT_CONFIGURATION, // bConfigurationValue
0x00, // iConfiguration
0x80, // bmAttributes
50, // bMaxPower
// Interface 0, Alternate Setting 0, Audio Control
INTERFACE_DESCRIPTOR_LENGTH, // bLength
INTERFACE_DESCRIPTOR, // bDescriptorType
0x00, // bInterfaceNumber
0x00, // bAlternateSetting
0x00, // bNumEndpoints
AUDIO_CLASS, // bInterfaceClass
SUBCLASS_AUDIOCONTROL, // bInterfaceSubClass
0x00, // bInterfaceProtocol
0x00, // iInterface
// Audio Control Interface
CONTROL_INTERFACE_DESCRIPTOR_LENGTH + 1,// bLength
INTERFACE_DESCRIPTOR_TYPE, // bDescriptorType
CONTROL_HEADER, // bDescriptorSubtype
LSB(0x0100), // bcdADC (LSB)
MSB(0x0100), // bcdADC (MSB)
LSB(TOTAL_CONTROL_INTF_LENGTH), // wTotalLength
MSB(TOTAL_CONTROL_INTF_LENGTH), // wTotalLength
0x02, // bInCollection
0x01, // baInterfaceNr
0x02, // baInterfaceNr
// Audio Input Terminal (Speaker)
INPUT_TERMINAL_DESCRIPTOR_LENGTH, // bLength
INTERFACE_DESCRIPTOR_TYPE, // bDescriptorType
CONTROL_INPUT_TERMINAL, // bDescriptorSubtype
0x01, // bTerminalID
LSB(TERMINAL_USB_STREAMING), // wTerminalType
MSB(TERMINAL_USB_STREAMING), // wTerminalType
0x00, // bAssocTerminal
channel_nb_in, // bNrChannels
(uint8_t)(LSB(channel_config_in)), // wChannelConfig
(uint8_t)(MSB(channel_config_in)), // wChannelConfig
0x00, // iChannelNames
0x00, // iTerminal
// Audio Feature Unit (Speaker)
FEATURE_UNIT_DESCRIPTOR_LENGTH, // bLength
INTERFACE_DESCRIPTOR_TYPE, // bDescriptorType
CONTROL_FEATURE_UNIT, // bDescriptorSubtype
0x02, // bUnitID
0x01, // bSourceID
0x01, // bControlSize
CONTROL_MUTE |
CONTROL_VOLUME, // bmaControls(0)
0x00, // bmaControls(1)
0x00, // iTerminal
// Audio Output Terminal (Speaker)
OUTPUT_TERMINAL_DESCRIPTOR_LENGTH, // bLength
INTERFACE_DESCRIPTOR_TYPE, // bDescriptorType
CONTROL_OUTPUT_TERMINAL, // bDescriptorSubtype
0x03, // bTerminalID
LSB(TERMINAL_SPEAKER), // wTerminalType
MSB(TERMINAL_SPEAKER), // wTerminalType
0x00, // bAssocTerminal
0x02, // bSourceID
0x00, // iTerminal
// Audio Input Terminal (Microphone)
INPUT_TERMINAL_DESCRIPTOR_LENGTH, // bLength
INTERFACE_DESCRIPTOR_TYPE, // bDescriptorType
CONTROL_INPUT_TERMINAL, // bDescriptorSubtype
0x04, // bTerminalID
LSB(TERMINAL_MICROPHONE), // wTerminalType
MSB(TERMINAL_MICROPHONE), // wTerminalType
0x00, // bAssocTerminal
channel_nb_out, // bNrChannels
(uint8_t)(LSB(channel_config_out)), // wChannelConfig
(uint8_t)(MSB(channel_config_out)), // wChannelConfig
0x00, // iChannelNames
0x00, // iTerminal
// Audio Output Terminal (Microphone)
OUTPUT_TERMINAL_DESCRIPTOR_LENGTH, // bLength
INTERFACE_DESCRIPTOR_TYPE, // bDescriptorType
CONTROL_OUTPUT_TERMINAL, // bDescriptorSubtype
0x05, // bTerminalID
LSB(TERMINAL_USB_STREAMING), // wTerminalType
MSB(TERMINAL_USB_STREAMING), // wTerminalType
0x00, // bAssocTerminal
0x04, // bSourceID
0x00, // iTerminal
// Interface 1, Alternate Setting 0, Audio Streaming - Zero Bandwith
INTERFACE_DESCRIPTOR_LENGTH, // bLength
INTERFACE_DESCRIPTOR, // bDescriptorType
0x01, // bInterfaceNumber
0x00, // bAlternateSetting
0x00, // bNumEndpoints
AUDIO_CLASS, // bInterfaceClass
SUBCLASS_AUDIOSTREAMING, // bInterfaceSubClass
0x00, // bInterfaceProtocol
0x00, // iInterface
// Interface 1, Alternate Setting 1, Audio Streaming - Operational
INTERFACE_DESCRIPTOR_LENGTH, // bLength
INTERFACE_DESCRIPTOR, // bDescriptorType
0x01, // bInterfaceNumber
0x01, // bAlternateSetting
0x01, // bNumEndpoints
AUDIO_CLASS, // bInterfaceClass
SUBCLASS_AUDIOSTREAMING, // bInterfaceSubClass
0x00, // bInterfaceProtocol
0x00, // iInterface
// Audio Streaming Interface
STREAMING_INTERFACE_DESCRIPTOR_LENGTH, // bLength
INTERFACE_DESCRIPTOR_TYPE, // bDescriptorType
STREAMING_GENERAL, // bDescriptorSubtype
0x01, // bTerminalLink
0x00, // bDelay
LSB(FORMAT_PCM), // wFormatTag
MSB(FORMAT_PCM), // wFormatTag
// Audio Type I Format
FORMAT_TYPE_I_DESCRIPTOR_LENGTH, // bLength
INTERFACE_DESCRIPTOR_TYPE, // bDescriptorType
STREAMING_FORMAT_TYPE, // bDescriptorSubtype
FORMAT_TYPE_I, // bFormatType
channel_nb_in, // bNrChannels
0x02, // bSubFrameSize
16, // bBitResolution
0x01, // bSamFreqType
(uint8_t)(LSB(FREQ_IN)), // tSamFreq
(uint8_t)((FREQ_IN >> 8) & 0xff), // tSamFreq
(uint8_t)((FREQ_IN >> 16) & 0xff), // tSamFreq
// Endpoint - Standard Descriptor
ENDPOINT_DESCRIPTOR_LENGTH + 2, // bLength
ENDPOINT_DESCRIPTOR, // bDescriptorType
PHY_TO_DESC(EPISO_OUT), // bEndpointAddress
E_ISOCHRONOUS, // bmAttributes
(uint8_t)(LSB(PACKET_SIZE_ISO_IN)), // wMaxPacketSize
(uint8_t)(MSB(PACKET_SIZE_ISO_IN)), // wMaxPacketSize
0x01, // bInterval
0x00, // bRefresh
0x00, // bSynchAddress
// Endpoint - Audio Streaming
STREAMING_ENDPOINT_DESCRIPTOR_LENGTH, // bLength
ENDPOINT_DESCRIPTOR_TYPE, // bDescriptorType
ENDPOINT_GENERAL, // bDescriptor
0x00, // bmAttributes
0x00, // bLockDelayUnits
LSB(0x0000), // wLockDelay
MSB(0x0000), // wLockDelay
// Interface 1, Alternate Setting 0, Audio Streaming - Zero Bandwith
INTERFACE_DESCRIPTOR_LENGTH, // bLength
INTERFACE_DESCRIPTOR, // bDescriptorType
0x02, // bInterfaceNumber
0x00, // bAlternateSetting
0x00, // bNumEndpoints
AUDIO_CLASS, // bInterfaceClass
SUBCLASS_AUDIOSTREAMING, // bInterfaceSubClass
0x00, // bInterfaceProtocol
0x00, // iInterface
// Interface 1, Alternate Setting 1, Audio Streaming - Operational
INTERFACE_DESCRIPTOR_LENGTH, // bLength
INTERFACE_DESCRIPTOR, // bDescriptorType
0x02, // bInterfaceNumber
0x01, // bAlternateSetting
0x01, // bNumEndpoints
AUDIO_CLASS, // bInterfaceClass
SUBCLASS_AUDIOSTREAMING, // bInterfaceSubClass
0x00, // bInterfaceProtocol
0x00, // iInterface
// Audio Streaming Interface
STREAMING_INTERFACE_DESCRIPTOR_LENGTH, // bLength
INTERFACE_DESCRIPTOR_TYPE, // bDescriptorType
SUBCLASS_AUDIOCONTROL, // bDescriptorSubtype
0x05, // bTerminalLink (output terminal microphone)
0x01, // bDelay
0x01, // wFormatTag
0x00, // wFormatTag
// Audio Type I Format
FORMAT_TYPE_I_DESCRIPTOR_LENGTH, // bLength
INTERFACE_DESCRIPTOR_TYPE, // bDescriptorType
SUBCLASS_AUDIOSTREAMING, // bDescriptorSubtype
FORMAT_TYPE_I, // bFormatType
channel_nb_out, // bNrChannels
0x02, // bSubFrameSize
0x10, // bBitResolution
0x01, // bSamFreqType
(uint8_t)(LSB(FREQ_OUT)), // tSamFreq
(uint8_t)((FREQ_OUT >> 8) & 0xff), // tSamFreq
(uint8_t)((FREQ_OUT >> 16) & 0xff), // tSamFreq
// Endpoint - Standard Descriptor
ENDPOINT_DESCRIPTOR_LENGTH + 2, // bLength
ENDPOINT_DESCRIPTOR, // bDescriptorType
PHY_TO_DESC(EPISO_IN), // bEndpointAddress
E_ISOCHRONOUS, // bmAttributes
(uint8_t)(LSB(PACKET_SIZE_ISO_OUT)), // wMaxPacketSize
(uint8_t)(MSB(PACKET_SIZE_ISO_OUT)), // wMaxPacketSize
0x01, // bInterval
0x00, // bRefresh
0x00, // bSynchAddress
// Endpoint - Audio Streaming
STREAMING_ENDPOINT_DESCRIPTOR_LENGTH, // bLength
ENDPOINT_DESCRIPTOR_TYPE, // bDescriptorType
ENDPOINT_GENERAL, // bDescriptor
0x00, // bmAttributes
0x00, // bLockDelayUnits
LSB(0x0000), // wLockDelay
MSB(0x0000), // wLockDelay
// Terminator
0 // bLength
};
return configDescriptor;
}
const uint8_t *USBAudio::stringIinterfaceDesc() {
static const uint8_t stringIinterfaceDescriptor[] = {
0x0c, //bLength
STRING_DESCRIPTOR, //bDescriptorType 0x03
'A',0,'u',0,'d',0,'i',0,'o',0 //bString iInterface - Audio
};
return stringIinterfaceDescriptor;
}
const uint8_t *USBAudio::stringIproductDesc() {
static const uint8_t stringIproductDescriptor[] = {
0x16, //bLength
STRING_DESCRIPTOR, //bDescriptorType 0x03
'M',0,'b',0,'e',0,'d',0,' ',0,'A',0,'u',0,'d',0,'i',0,'o',0 //bString iProduct - Mbed Audio
};
return stringIproductDescriptor;
}