在本篇blog中，我们学习如何在UVC 应用中实现对图像属性的控制。本篇笔记中应用到的 固件 为 第四篇笔记 的附件，硬件 为 CX3 Denebola 板。
从 UVC 1.5 协议上可以看到，亮度控制属于 processing unit的内容，必需支持的控制命令有 SET_CUR、GET_CUR、GET_MIN、GET_MAX、GET_RES、GET_INFO 和 GET_DEF。
首先，在cycx3_uvcdscr.c 描述符文件中找到 processing unit 描述符部分
/* Processing Unit Descriptor */
0x0D, /* Descriptor size */
CX3_CS_INTRFC_DESCR, /* Class specific interface desc type */
0x05, /* Processing Unit Descriptor type: VC_PROCESSING_UNIT*/
0x02, /* ID of this unit */
0x01, /* Source ID: 1: Conencted to input terminal */
0x00, 0x40, /* Digital multiplier */
0x03, /* Size of controls field for this terminal: 3 bytes */
0x00, 0x00, 0x00, /* No controls supported */
0x00, /* String desc index: Not used */
0x00, /* Analog Video Standards Supported: None */
查询 UVC 协议可以看到，Byte 8/9/10 用来指定UVC支持哪些控制属性。
可以看到，bit[0] 用来指定是否支持亮度控制，所以这里我们将 bit[0] 设置为1.
/* Processing Unit Descriptor */
0x0D, /* Descriptor size */
CX3_CS_INTRFC_DESCR, /* Class specific interface desc type */
0x05, /* Processing Unit Descriptor type: VC_PROCESSING_UNIT*/
0x02, /* ID of this unit */
0x01, /* Source ID: 1: Conencted to input terminal */
0x00, 0x40, /* Digital multiplier */
0x03, /* Size of controls field for this terminal: 3 bytes */
0x01, 0x00, 0x00, /* Brigntness control is supported */
0x00, /* String desc index: Not used */
0x00, /* Analog Video Standards Supported: None */
在函数 CyCx3UvcAppUSBSetupCB 中添加如下代码
#ifdef Add_brightness_control
/* Handle Video control commands here*/
status = HandleVCInterfaceRequest(wIndex, wValue, bRequest);
if (status != CY_U3P_SUCCESS)
{
CyU3PDebugPrint (4, "\n\rUSBStpCB:VCI SendEP0Data = %d", status);
isHandled=CyFalse;
}
else
isHandled = CyTrue;
#endif
添加 定义
#ifdef Add_brightness_control
CyU3PReturnStatus_t HandleVCInterfaceRequest(uint16_t wIndex, uint16_t wValue,uint8_t bRequest)
{
CyU3PReturnStatus_t status = CY_U3P_ERROR_BAD_ARGUMENT;
if (CY_U3P_GET_MSB(wIndex) == CX3_UVC_VC_PROCESSING_UNIT_ID) /*Video Control- Camera Teminal*/
{
CyU3PDebugPrint(4,"\n\r\n\rLine:%d\tVC:T ID 0x%x CS 0x%x Req 0x%x ", __LINE__,CY_U3P_GET_MSB(wIndex), wValue, bRequest);
switch (wValue)
{
case CX3_UVC_PU_BRIGHTNESS_CONTROL: /*LED control*/
CyU3PDebugPrint(4,"\r\n Brightness control\n");
status = HandleBrightnessControlReq(bRequest);
break;
default:
// glerrorstatus = VC_ERROR_CODE_INVALID_CONTROL;
break;
}
}
return status;
}
CyU3PReturnStatus_t HandleBrightnessControlReq(uint8_t bRequest)
{
CyU3PReturnStatus_t status=1;
uint16_t readCount;
uint8_t WrBuff[2]={0,0},RdBuff;
switch(bRequest)
{
case CX3_USB_UVC_GET_CUR_REQ:
WrBuff[0] = Brightness.CurrentVal;
CyU3PDebugPrint(4,"\r\nLine:%d UVC Brightness get cur %d\n",__LINE__,WrBuff);
break;
case CX3_USB_UVC_SET_CUR_REQ:
status = CyU3PUsbGetEP0Data (2, &WrBuff[0], &readCount);
CyU3PDebugPrint(4,"\r\n Line:%d UVC brightness set cur %d\n",__LINE__,WrBuff);
return status;
break;
case CX3_USB_UVC_GET_MIN_REQ:
WrBuff[0] = Brightness.MinVal;
CyU3PDebugPrint(4,"\r\n Line:%d UVC brightness get Min %d\n",__LINE__,WrBuff);
break;
case CX3_USB_UVC_GET_MAX_REQ:
WrBuff[0] = Brightness.MinVal;
CyU3PDebugPrint(4,"\r\n Line:%d UVC brightness get Max %d\n",__LINE__,WrBuff);
break;
case CX3_USB_UVC_GET_RES_REQ:
WrBuff[0] = Brightness.Res;
CyU3PDebugPrint(4,"\r\n Line:%d UVC brightness get RES %d\n",__LINE__,WrBuff);
break;
case CX3_USB_UVC_GET_INFO_REQ:
WrBuff[0] = Brightness.Info;
CyU3PDebugPrint(4,"\r\n Line:%d UVC brightness get INFO %d\n",__LINE__,WrBuff);
break;
case CX3_USB_UVC_GET_DEF_REQ:
WrBuff[0] = Brightness.DefaultVal;
CyU3PDebugPrint(4,"\r\n Line:%d UVC brightness get default %d\n",__LINE__,WrBuff);
break;
case CX3_USB_UVC_GET_LEN_REQ:
WrBuff[0] = 2;
CyU3PDebugPrint(4,"\r\n Line:%d UVC brightness get len %d\n",__LINE__,WrBuff);
break;
default:
CyU3PUsbStall(0,CyTrue,CyFalse);
break;
}
status = CyU3PUsbSendEP0Data(2,(uint8_t*)&WrBuff);
if (status != 0)
{
CyU3PDebugPrint(4,"\n\r Send EP0 Data failed = 0x%X", status);
}
return status;
}
#endif
关于其他必要的变量定义和函数声明，请参考附件工程。编译工程并下载到Demo板中，在E-cam viewer属性面板中我们可以看到 亮度控制已经使能。
更多细节信息，请参考附件工程。
添加其他控制属性的步骤和亮度控制的步骤方法一致，这里就不再重复。