DIY - PIC：PIC18F4550 USB PIC 端程式 (六十八)

DIY - PIC：PIC18F4550 USB PIC 端程式 (六十八)：

Microchip 18F4550 單片機系列晶片有提供了面向不同客戶群的 DEMO 程式，可以減輕了系統開發人員的負擔，同時縮短了開發週期。

USB Framework 固件網址：Microchip Application Libraries v2010-10-19 

程式選用了 USB Device - HID - Custom Demos程式。HID (Human Interface Devices，人機接口設備）是一類的 USB 設備，讓結構的數據，將在設備之間傳輸和主機電腦。在枚舉過程，設備描述信息，它可以接收和發送。USB 通信都是通過中斷來完成的，在 USB 中斷服務程式內，要實現輸入／輸出介面，允許大多數的USB程式在後台完成，電腦主機處理的數據接收從 USB 設備而不需要一個特別設計的設備驅動程序。

USB Device - HID - Custom Demos (目錄下的子目錄) 
└ Generic HID – Firmware 
└ Generic HID - HID DLL - PC Software 
└ Generic HID - PnP Demo - PC Software 
└ Generic HID - Simple Demo - PC Software

USB 程式的設計就是在 Microchip 公司提供的 DEMO 程式的基礎上，進行必要的修改來完成的。

Generic HID – Firmware (子目錄下的文件) 
└ main.c 
└ usb_config.c 
└ usb_descriptors.c 
└ HardwareProfile - PICDEM FSUSB.c 
└ USB Device - HID - Simple Custom Demo - C18 - PICDEM FSUSB.mcw 

Microchip (微芯) 提供了一系列的 USB 寄存器，使用這些寄存器可以完成 USB 通信。大多數的 USB 通信都是通過中斷來完成的，在 USB 中斷服務程式內，要實現輸入／輸出介面，允許大多數的 USB 程式在後台完成。從應用的觀點來看，枚舉過程和資料通信的發生好像沒有聯繫。 

在系統主程序 (main.c) 內的 ProcessIO修改， 18F4550 的 USB 接收到 PC 送來的指令，18F4550 便會作出不同的操作，如 開關 LED、讀 ADC 數值或讀出控鍵狀態。
 

void ProcessIO(void) {       //Blink the LEDs according to the USB device status     if(blinkStatusValid)     {         BlinkUSBStatus();     }     // User Application USB tasks     if((USBDeviceState < CONFIGURED_STATE)||(USBSuspendControl==1)) return;         if(!HIDRxHandleBusy(USBOutHandle))     //Check if data was received from the host.     {           switch(ReceivedDataBuffer[0])                //Look at the data the host sent, to see what kind                                                                                  of application specific command it sent.         {             case 0x80:  //Toggle LEDs command                 blinkStatusValid = FALSE;            //Stop blinking the LEDs automatically, going to                                                                               manually control them now.                 if(mGetLED_1() == mGetLED_2())                 {                     mLED_1_Toggle();                     mLED_2_Toggle();                 }                 else                 {                     if(mGetLED_1())                     {                         mLED_2_On();                     }                     else                     {                         mLED_2_Off();                     }                 }                                 break;             case 0x81:  //Get push button state                 ToSendDataBuffer[0] = 0x81;                //Echo back to the host PC the command we are                                                                                       fulfilling in the first byte.  In this case, the Get                                                                                       Pushbutton State command.                 if(sw3 == 1)                            //pushbutton not pressed, pull up resistor on circuit                                                                    board is pulling the PORT pin high                 {                     ToSendDataBuffer[1] = 0x01;                            }                 else        //sw3 must be == 0, pushbutton is pressed and overpowering the pull up resistor                 {                     ToSendDataBuffer[1] = 0x00;                 }                 if(!HIDTxHandleBusy(USBInHandle))                 {                     USBInHandle = HIDTxPacket(HID_EP,(BYTE*)&ToSendDataBuffer[0],64);                 }                 break;             case 0x37:    //Read POT command.  Uses ADC to measure an analog voltage                                     on one of the ANxx I/O pins, and returns the result to the host                 {                     WORD_VAL w;                     if(!HIDTxHandleBusy(USBInHandle))                     {                         mInitPOT();                         w = ReadPOT();    //Use ADC to read the I/O pin voltage.  See the relevant                                                             HardwareProfile - xxxxx.h file for the I/O pin that it will measure.                                                         //Some demo boards, like the PIC18F87J50 FS USB Plug-In                                                            Module board, do not have a potentiometer (when used stand alone).                                                         //This function call will still measure the analog voltage on the                                                            I/O pin however.  To make the demo more interesting, it                                                         //is suggested that an external adjustable analog voltage should be applied to this pin.                         ToSendDataBuffer[0] = 0x37;      //Echo back to the host the command we are fulfilling in the first byte.  In this case, the Read POT (analog voltage) command.                         ToSendDataBuffer[1] = w.v[0];      //Measured analog voltage LSB                         ToSendDataBuffer[2] = w.v[1];      //Measured analog voltage MSB                         USBInHandle = HIDTxPacket(HID_EP,(BYTE*)&ToSendDataBuffer[0],64);         LcdSetLine2();                        // Put cursor on start of line 2         printf("D=%04i",w);                     }                                    }                 break;         }         //Re-arm the OUT endpoint for the next packet         USBOutHandle = HIDRxPacket(HID_EP,(BYTE*)&ReceivedDataBuffer,64);     }     }//end ProcessIO

▲  ProcessIO 子程式

▲ 紅圈是 USB 主要的控制設備

▲ LCD1602 顯示 ADC 的數據

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