我正在 Atmega32U4 上实现 USB 网络摄像头。
我想我设法在控制端点上实现了事务，或多或少正确，因为所有描述符都在系统中传输并且设备报告正确。
问题是当我尝试从设备发送视频数据时，似乎什么都没有通过。
我实现数据传输的方式（根据datasheet的22.14节）如下：
while (len > 0) {
while (1) {
cli();
_select_endpoint(VIDEO_STREAMING_ENDPOINT);
if (bit_is_set(UEINTX, TXINI) && bit_is_set(UEINTX, FIFOCON))
break;
sei();
_delay_ms(1);
}
_clear_TXINI();
while (bit_is_set(UEINTX, RWAL) && len > 0) {
UEDATX = *buff++;
--len;
}
_clear_FIFOCON();
sei();
}
在调试时，我注意到在第一个循环期间银行充满了数据，但数据没有传输到主机。它在 TXINI,FIFOCON 部分永远循环。Wireshark 中除了控制请求外，什么都没有显示。我不确定我是否在 MCU 寄存器上配置错误，所以它没有根据请求向主机发送数据，或者在描述符、状态等中，所以主机没有请求数据。
我可能搞砸了什么？
lsusb -v
Bus 001 Device 077: ID 6431:deb2 majkrzak majkrzak
Device Descriptor:
bLength 18
bDescriptorType 1
bcdUSB 2.00
bDeviceClass 239 Miscellaneous Device
bDeviceSubClass 2
bDeviceProtocol 1 Interface Association
bMaxPacketSize0 32
idVendor 0x6431
idProduct 0xdeb2
bcdDevice 0.00
iManufacturer 1 majkrzak
iProduct 1 majkrzak
iSerial 1 majkrzak
bNumConfigurations 1
Configuration Descriptor:
bLength 9
bDescriptorType 2
wTotalLength 0x00a0
bNumInterfaces 2
bConfigurationValue 1
iConfiguration 1 majkrzak
bmAttributes 0x80
(Bus Powered)
MaxPower 500mA
Interface Association:
bLength 8
bDescriptorType 11
bFirstInterface 0
bInterfaceCount 2
bFunctionClass 14 Video
bFunctionSubClass 3 Video Interface Collection
bFunctionProtocol 0
iFunction 1 majkrzak
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 0
bAlternateSetting 0
bNumEndpoints 0
bInterfaceClass 14 Video
bInterfaceSubClass 1 Video Control
bInterfaceProtocol 1
iInterface 1 majkrzak
VideoControl Interface Descriptor:
bLength 13
bDescriptorType 36
bDescriptorSubtype 1 (HEADER)
bcdUVC 1.50
wTotalLength 0x0028
dwClockFrequency 16.000000MHz
bInCollection 1
baInterfaceNr( 0) 1
VideoControl Interface Descriptor:
bLength 18
bDescriptorType 36
bDescriptorSubtype 2 (INPUT_TERMINAL)
bTerminalID 1
wTerminalType 0x0201 Camera Sensor
bAssocTerminal 2
iTerminal 1 majkrzak
wObjectiveFocalLengthMin 0
wObjectiveFocalLengthMax 0
wOcularFocalLength 0
bControlSize 3
bmControls 0x00000000
VideoControl Interface Descriptor:
bLength 9
bDescriptorType 36
bDescriptorSubtype 3 (OUTPUT_TERMINAL)
bTerminalID 2
wTerminalType 0x0101 USB Streaming
bAssocTerminal 1
bSourceID 1
iTerminal 1 majkrzak
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 1
bAlternateSetting 0
bNumEndpoints 1
bInterfaceClass 14 Video
bInterfaceSubClass 2 Video Streaming
bInterfaceProtocol 1
iInterface 1 majkrzak
VideoStreaming Interface Descriptor:
bLength 13
bDescriptorType 36
bDescriptorSubtype 1 (INPUT_HEADER)
bNumFormats 1
wTotalLength 0x0055
bEndpointAddress 0x81 EP 1 IN
bmInfo 0
bTerminalLink 2
bStillCaptureMethod 0
bTriggerSupport 0
bTriggerUsage 0
bControlSize 0
bmaControls( 0) 27
VideoStreaming Interface Descriptor:
bLength 27
bDescriptorType 36
bDescriptorSubtype 4 (FORMAT_UNCOMPRESSED)
bFormatIndex 1
bNumFrameDescriptors 1
guidFormat {32595559-0000-0010-8000-00aa00389b71}
bBitsPerPixel 8
bDefaultFrameIndex 0
bAspectRatioX 1
bAspectRatioY 1
bmInterlaceFlags 0x00
Interlaced stream or variable: No
Fields per frame: 2 fields
Field 1 first: No
Field pattern: Field 1 only
bCopyProtect 0
VideoStreaming Interface Descriptor:
bLength 38
bDescriptorType 36
bDescriptorSubtype 5 (FRAME_UNCOMPRESSED)
bFrameIndex 1
bmCapabilities 0x02
Still image unsupported
Fixed frame-rate
wWidth 16
wHeight 16
dwMinBitRate 262144
dwMaxBitRate 262144
dwMaxVideoFrameBufferSize 768
dwDefaultFrameInterval 1000000
bFrameIntervalType 0
dwMinFrameInterval 1000000
dwMaxFrameInterval 1000000
dwFrameIntervalStep 0
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x81 EP 1 IN
bmAttributes 2
Transfer Type Bulk
Synch Type None
Usage Type Data
wMaxPacketSize 0x0020 1x 32 bytes
bInterval 1
Device Status: 0x0000
(Bus Powered)
编辑
我制作了一个简单的脚本，pyusb用于从端点提取数据并且它可以工作。Wireshark 正在显示交易，因此这意味着在这种uvcvideo情况下根本不会提取数据。我当时肯定搞砸了描述符。