Embedded Lab

USB HID

Most of the common devices like keyboards, mice, printers, scanners, barcode readers, gamepads, etc that we use with our PCs and laptops in regular life are USB HID devices. We can use our MSP430F5529 microcontroller to make USB HID devices and in this example, we will use our MSP430 microcontroller to make a rudimentary mouse. Unlike conventional mice, our mouse will be using a keypad joystick instead of optoelectronics or mechanical trackball.

Code Example

#include "driverlib.h"
#include "delay.h"
#include "lcd.h"
#include "lcd_print.h"

#include "USB_config/descriptors.h"
#include "USB_API/USB_Common/device.h"
#include "USB_API/USB_Common/usb.h"
#include "USB_API/USB_HID_API/UsbHid.h"

#include "hal.h"

#define LED_PORT            GPIO_PORT_P4
#define LED_PIN             GPIO_PIN7

#define MOUSE_PORT          GPIO_PORT_P6
#define MOUSE_UP_PIN        GPIO_PIN0
#define MOUSE_DOWN_PIN      GPIO_PIN1
#define MOUSE_LEFT_PIN      GPIO_PIN2
#define MOUSE_RIGHT_PIN     GPIO_PIN3
#define MOUSE_BUTTON_PIN    GPIO_PIN4

#define change_amount       1

typedef struct
{
    int8_t buttons;
    int8_t dX;
    int8_t dY;
    int8_t dZ;
}MOUSE_REPORT;

MOUSE_REPORT mouseReport = {0x00, 0x00, 0x00, 0x00};

void DIO_init(void);

#pragma vector = UNMI_VECTOR
__interrupt void UNMI_ISR (void)
{
    switch (__even_in_range(SYSUNIV, SYSUNIV_BUSIFG ))
    {
        case SYSUNIV_NONE:
        {
            __no_operation();
            break;
        }

        case SYSUNIV_NMIIFG:
        {
            __no_operation();
            break;
        }

        case SYSUNIV_OFIFG:
        {
            UCS_clearFaultFlag(UCS_XT2OFFG);
            UCS_clearFaultFlag(UCS_DCOFFG);
            SFR_clearInterrupt(SFR_OSCILLATOR_FAULT_INTERRUPT);
            break;
        }

        case SYSUNIV_ACCVIFG:
        {
            __no_operation();
            break;
        }
        case SYSUNIV_BUSIFG:
        {
            SYSBERRIV = 0;
            USB_disable();
        }
    }
}

void main (void)
{
    unsigned char t = 0x0000;

    WDT_A_hold(WDT_A_BASE);

    LCD_init();
    LCD_clear_home();

    LCD_goto(1, 0);
    LCD_putstr("MSP430 USB HID");

    LCD_goto(0, 1);
    LCD_putstr("X: ");

    LCD_goto(6, 1);
    LCD_putstr("Y:");

    LCD_goto(12, 1);
    LCD_putstr("B:");

    PMM_setVCore(PMM_CORE_LEVEL_2);
    USBHAL_initPorts();
    USBHAL_initClocks(8000000);
    USB_setup(TRUE, TRUE);

    DIO_init();

    __enable_interrupt();

    while (1)
    {
        if(GPIO_getInputPinValue(MOUSE_PORT,
                                 MOUSE_UP_PIN) == false)
        {
            mouseReport.dY += change_amount;
        }

        if(GPIO_getInputPinValue(MOUSE_PORT,
                                 MOUSE_DOWN_PIN) == false)
        {
            mouseReport.dY -= change_amount;
        }

        if(mouseReport.dY > 127)
        {
            mouseReport.dY = 127;
        }

        if(mouseReport.dY  127)
        {
            mouseReport.dX = 127;
        }

        if(mouseReport.dX  40)
        {
            t = 0;
            mouseReport.dX = 0;
            mouseReport.dY = 0;
            mouseReport.buttons = 0;
        }
    }
}


void DIO_init(void)
{
    GPIO_setAsInputPinWithPullUpResistor(MOUSE_PORT,
                                         MOUSE_UP_PIN);

    GPIO_setAsInputPinWithPullUpResistor(MOUSE_PORT,
                                         MOUSE_DOWN_PIN);

    GPIO_setAsInputPinWithPullUpResistor(MOUSE_PORT,
                                         MOUSE_LEFT_PIN);

    GPIO_setAsInputPinWithPullUpResistor(MOUSE_PORT,
                                         MOUSE_RIGHT_PIN);

    GPIO_setAsInputPinWithPullUpResistor(MOUSE_PORT,
                                         MOUSE_BUTTON_PIN);
}

Hardware Setup

Explanation

Just like the past example, again we are interested in the main loop as everything is done here. On each press of joystick buttons x and y coordinates are changed by 1 unit. We are not using mouse coordinate acceleration as with any regular mouse and that is why the change amount is 1 unit only. On PC screen, the mouse cursor will appear to move slowly as if the PC is busy doing some other works. We are also assuming that the x and y coordinate boundaries range from -127 to +127 units. In the code, we have to take care that these extremes are not exceeded. We are not using typical mouse click buttons although I coded the joystick middle button for clicking. This is not very important here as mouse cursor movement is all that is needed for USB HID demo. In the ST_ENUM_ACTIVE case, the location of cursor and button state are reported to host PC. The PC then uses these to change the position of the mouse cursor.

while (1)
{
    if(GPIO_getInputPinValue(MOUSE_PORT, MOUSE_UP_PIN) == false)
    {
        mouseReport.dY += change_amount;
    }

    if(GPIO_getInputPinValue(MOUSE_PORT, MOUSE_DOWN_PIN) == false)
    {
        mouseReport.dY -= change_amount;
    }
   
    if(mouseReport.dY > 127)
    {
        mouseReport.dY = 127;
    }

    if(mouseReport.dY  127)
    {
        mouseReport.dX = 127;
    }

    if(mouseReport.dX  40)
     {
         t = 0;
         mouseReport.dX = 0;
         mouseReport.dY = 0;
         mouseReport.buttons = 0;
      }
}

For 40 times, the mouse’s coordinate changes and button states are not reset automatically and this is so because we don’t want to keep holding the joystick buttons for movement once our desired speed is achieved. Remember no acceleration is used.

Demo

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