83 lines
3.5 KiB
ReStructuredText
83 lines
3.5 KiB
ReStructuredText
usbd_video
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===============
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本节主要演示 USB UAC 功能，支持 YUYV, MJPEG, H264 格式。为了方便演示，都采用的静态图。
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demo 包含 **video_static_yuyv_template**, **video_static_mjpeg_template**, **video_static_h264_template**, 仅描述符和图片数据不同。
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- 在高速模式下，默认最大是1024字节，但是如果芯片支持 additional transcations，可以配置为最高 2048字节或者3072字节，这样可以提高传输效率。
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.. code-block:: C
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#ifdef CONFIG_USB_HS
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#define MAX_PAYLOAD_SIZE 1024 // for high speed with one transcations every one micro frame
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#define VIDEO_PACKET_SIZE (unsigned int)(((MAX_PAYLOAD_SIZE / 1)) | (0x00 << 11))
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// #define MAX_PAYLOAD_SIZE 2048 // for high speed with two transcations every one micro frame
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// #define VIDEO_PACKET_SIZE (unsigned int)(((MAX_PAYLOAD_SIZE / 2)) | (0x01 << 11))
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// #define MAX_PAYLOAD_SIZE 3072 // for high speed with three transcations every one micro frame
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// #define VIDEO_PACKET_SIZE (unsigned int)(((MAX_PAYLOAD_SIZE / 3)) | (0x02 << 11))
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#else
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#define MAX_PAYLOAD_SIZE 1020
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#define VIDEO_PACKET_SIZE (unsigned int)(((MAX_PAYLOAD_SIZE / 1)) | (0x00 << 11))
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#endif
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- 通常只需要修改 WIDTH 和 HEIGHT
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.. code-block:: C
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#define WIDTH (unsigned int)(640)
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#define HEIGHT (unsigned int)(480)
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#define CAM_FPS (30)
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#define INTERVAL (unsigned long)(10000000 / CAM_FPS)
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#define MIN_BIT_RATE (unsigned long)(WIDTH * HEIGHT * 16 * CAM_FPS) //16 bit
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#define MAX_BIT_RATE (unsigned long)(WIDTH * HEIGHT * 16 * CAM_FPS)
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#define MAX_FRAME_SIZE (unsigned long)(WIDTH * HEIGHT * 2)
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- USB 端点配置，默认 interval 为 1，也就是全速模式下 1ms，高速模式下 125us。同步类型使用异步模式。
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.. code-block:: C
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/* 1.2.2.2 Standard VideoStream Isochronous Video Data Endpoint Descriptor */
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USB_ENDPOINT_DESCRIPTOR_INIT(VIDEO_IN_EP, 0x05, VIDEO_PACKET_SIZE, 0x01),
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- 使用 `usbd_video_stream_start_write` 传输数据
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1，传输采用双缓冲的形式， **MAX_PACKETS_IN_ONE_TRANSFER** 表示一次传输可以携带多少个 **MAX_PAYLOAD_SIZE**，通常 IP 只能为 1。
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2，在中断完成中，调用 `usbd_video_stream_split_transfer` 继续下一次传输，直到返回为 true 表示传输完成。这边的分裂传输只是表示将图片数据拆成 **MAX_PACKETS_IN_ONE_TRANSFER * MAX_PAYLOAD_SIZE** 份传输。
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3，通常 IP 不支持一次传输非常大的数据，比如传输 1MB，因此需要做分裂传输，但是会增加中断次数。并且一次传输非常大数据也是需要足够的 RAM。
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.. code-block:: C
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void usbd_video_iso_callback(uint8_t busid, uint8_t ep, uint32_t nbytes)
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{
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if (usbd_video_stream_split_transfer(busid, ep)) {
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/* one frame has done */
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iso_tx_busy = false;
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}
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}
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USB_NOCACHE_RAM_SECTION USB_MEM_ALIGNX uint8_t packet_buffer[2][MAX_PACKETS_IN_ONE_TRANSFER * MAX_PAYLOAD_SIZE];
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void video_test(uint8_t busid)
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{
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memset(packet_buffer, 0, sizeof(packet_buffer));
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while (1) {
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if (tx_flag) {
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iso_tx_busy = true;
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usbd_video_stream_start_write(busid, VIDEO_IN_EP, &packet_buffer[0][0], &packet_buffer[1][0], MAX_PACKETS_IN_ONE_TRANSFER * MAX_PAYLOAD_SIZE, (uint8_t *)cherryusb_mjpeg, sizeof(cherryusb_mjpeg));
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while (iso_tx_busy) {
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if (tx_flag == 0) {
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break;
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}
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}
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}
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}
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} |