---
tags: 單晶片
---
# 2020單晶片課程：USBHost解答
## USB - 簡介
Universal Serial Bus 簡稱USB，中文稱之通用性串列匯流排，目前此介面已經非常廣泛運用在PC/NB的周邊裝置，甚至是移動式裝置對外設備輸出/輸入的應用。它的價值可以透過業界的泛用與使用者的愛戴，已經有很多文件與相關網路充分說明其優勢，其身影可從電腦周邊裝置的HID (Human Interface Device) 鍵盤滑鼠、隨身碟（USB Memory Stick、Pen Storage Drive、Flash Drive）到各種影像/聲音輸出入裝置(Webcam、Microphone、DVB-T Receiver)，更擴大應用至其它通訊裝置與外掛裝置(Bluetooth, Infrared, DVD burner)，甚至是取代和模擬舊式通訊Serial Port (如:RS232/422/485、PS/2)，進而作為當代PC的基本配備。
## How usb works
USB Host & USB device
## Library
[USBHost](https://os.mbed.com/users/mbed_official/code/USBHost/)
## LAB 1
Mouse 顯示滑鼠資訊，並控制LED燈

**左鍵led1 ; 右鍵led2 ; 中鍵led3**

**hint : 使用 Thread 、 attachEvent()**

{%youtube Pu2uWSzeQ7w %}
{%youtube Ur8RQOxKqvI %}

code

#include "mbed.h"
#include "USBHostMouse.h"

DigitalOut led1(LED1);
DigitalOut led2(LED2);
DigitalOut led3(LED3);

int status = 0;

void onMouseEvent(uint8_t buttons, int8_t x, int8_t y, int8_t z) {
    printf("buttons: %d, x: %d, y: %d, z: %d\r\n", buttons, x, y, z);
    status = buttons;
}
 
void mouse_task(void const *) {

    USBHostMouse mouse;
    printf("mouse started\n");
    while(1) {
       
        // try to connect a USB mouse
        while(!mouse.connect())
            Thread::wait(500);

        // when connected, attach handler called on mouse event
        mouse.attachEvent(onMouseEvent);

        // wait until the mouse is disconnected
        while(mouse.connected())
            Thread::wait(500);
        printf("mouse seen disconnected\n");
    }
}

int main() {
    Thread mouseTask(mouse_task);
    
    while(1) {
        if (status == 1){
            led1=1; led2=0; led3=0;
        }else if (status == 2){
            led1=0; led2=1; led3=0;
        }
        else if (status == 4){
            led1=0; led2=0; led3=1;
        }else{
            led1=0; led2=0; led3=0;    
        }
        Thread::wait(100);
    }
}

## LAB 2
Keyboard 顯示使用者輸入字母或符號

**hint : attach()**

{%youtube TFmp9rXsdCM %}

code

#include "mbed.h"
#include "USBHostKeyboard.h"

void onKey(uint8_t key) {
    printf("Key: %c\r\n", key);
}

void keyboard_task(void const *) {
    
    USBHostKeyboard keyboard;
    
    while(1) {
        // try to connect a USB keyboard
        while(!keyboard.connect())
            Thread::wait(500);
    
        // when connected, attach handler called on keyboard event
        keyboard.attach(onKey);
        
        // wait until the keyboard is disconnected
        while(keyboard.connected())
            Thread::wait(500);
    }
}

int main() {
    Thread keyboardTask(keyboard_task);
    
    while(1) {

    }
}