USB HID Mouse Driver using LPC2148

Tsuneo,

I'm soon going to be looking at USB on ARM.

Thank you so much for those links - Some very good bedtime reading :)

Hi Tsuneo,

Thanks for those documents.

I tried both the ways...

1. Changed all the descriptor tables as mentioned in the HID1_1.pdf like:

const U8 HID_ReportDescriptor[] = {
        0x05,0x01,
        0x09,0x02,
        0xA1,0x01,
        0x09,0x01,
        0xA1,0x00,
        0x05,0x09,
        0x19,0x01,
        0x29,0x03,
        0x15,0x00,
        0x25,0x01,
        0x95,0x03,
        0x75,0x01,
        0x81,0x02,
        0x95,0x01,
        0x75,0x05,
        0x81,0x01,
        0x05,0x01,
        0x09,0x30,
        0x09,0x31,
        0x15,0x81,
        0x25,0x7F,
        0x75,0x08,
        0x95,0x02,
        0x81,0x06,
        0xC0,
        0xC0
};

const U16 HID_ReportDescSize = sizeof(HID_ReportDescriptor);


/* USB Standard Device Descriptor */
const U8 USB_DeviceDescriptor[] = {
        0x12,
        0x01,
        WBVAL(0x100),
        0x00,
        0x00,
        0x00,
        0x08,
        WBVAL(0xFFFF),
        WBVAL(0x0001),
        WBVAL(0x0100),
        0x04,
        0x0E,
        0x30,
        0x01
};

/* USB Configuration Descriptor */
/*   All Descriptors (Configuration, Interface, Endpoint, Class, Vendor) */
const U8 USB_ConfigDescriptor[] = {
/* Configuration 1 */
        0x09,
        0x02,
        WBVAL(0x003),
        0x02,
        0x01,
        0x00,
        0xA0,
        0x32,
/* Interface 0, Alternate Setting 0, HID Class */
        0x09,
        0x04,
        0x01,
        0x00,
        0x01,
        0x03,
        0x01,
        0x02,
        0x00,
/* HID Class Descriptor */
/* HID_DESC_OFFSET = 0x0012 */
        0x09,
        0x21,
        WBVAL(0x101),
        0x00,
        0x01,
        0x22,
        0x32,
/* Endpoint, HID Interrupt In */
        0x07,
        0x05,
        0x82,
        0x03,
        WBVAL(0x0008),
        0x0A,
/* Terminator */
  0                                  /* bLength */
};

2. I kept the the other descriptor as it is and changed only Report, Interface, HID, Endpoint descriptor.
String Descriptor remains the same.
Both the ways windows could not detect the board as HID Mouse.

Am I missing something?

One more question, How should i send the mouse data to pc ? What should be its format?

Hi Tsuneo,

I made the Report Descriptor in readable format now:-)

const U8 HID_ReportDescriptor[] = {
        HID_UsagePage(HID_USAGE_PAGE_GENERIC),
        HID_Usage(HID_USAGE_GENERIC_MOUSE),
        HID_Collection (HID_Application),
          HID_Usage (HID_USAGE_GENERIC_POINTER),
          HID_Collection (HID_Physical),
            HID_ReportCount (3),
            HID_ReportSize (1),
            HID_UsagePage (HID_USAGE_PAGE_BUTTON),
            HID_UsageMin (1),
            HID_UsageMax (3),
            HID_LogicalMin (0),
            HID_LogicalMax (1),
            HID_Input (HID_Data | HID_Variable | HID_Absolute),
            HID_ReportCount (1),
            HID_ReportSize (5),
            HID_Input (HID_Constant),
            HID_ReportSize (8),
            HID_ReportCount (2),
            HID_UsagePage(HID_USAGE_PAGE_GENERIC),
            HID_Usage(HID_USAGE_GENERIC_X),
            HID_Usage(HID_USAGE_GENERIC_Y),
            HID_LogicalMin(0x81),
            HID_LogicalMax (0x7F),
            HID_Input (HID_Data | HID_Variable | HID_Relative),
          HID_EndCollection,
        HID_EndCollection
};

As the USB mouse protocol requires 3 bytes of Data (Button, X Displacement, Y Displacement), I declared U8 InReport as

U8 InReport[3] = {0};

void GetInReport (void) function does nothing (Code stubing will be done later)

I feel by doing so, it should work but....:-( It is still not working...

Are there any other changes i need to take care ?

Thanks & Regards,
Kamal Joshi

Are you working on Keil HID example?

Then, you don't need to swap entire descriptors.
Replace just the report descriptor.

I see some errors on the config descriptor set in above post, for example, wTotalLength field. But it's pain to examine the figures without any comment for the fields.
I recomend you to recover the original descriptors from the example.

For other change,

demo.c

BYTE InReport[3];      /* HID Input Report - 3 bytes for mouse */

/*
 *  Get HID Input Report -> InReport
 */

void GetInReport (void) {
  //
  //  Fill InReport[]
  //
  //   InReport[0]    mouse buttons, bit 0: left, bit 1: right, bit2: middle
  //   InReport[1]    X axis relative movement
  //   InReport[2]    Y axis relative movement
  //
}

Tsuneo

Hello guys,

I am a first timer with USB and like many others, VERY CONFUSED.

To start with, i have downloaded the example code for USBHID for LPC2368 and it is not working, leading to more confusion but most of them are conceptual and here are a few of them :

1. How will the code call the functions usbcore.c ?

2. How will the code initialize the descriptors and endpoints ?

Any help will be greatly appreciated.

Thanks.
Nitin

Don't you think you should start with a new thread, instead of hijacking someone elses?

Yes, I should have.

Apologies for that.

Can you please tell me how to start a new one ?

Thanks.

Got it ..

Thanks.

Please Help Tsuneo !

Sorry for posting here again.

Sorry, I repost my report descriptor:

static UNS_8 abReportDesc[] = {
  HID_UsagePage(HID_USAGE_PAGE_GENERIC),
  HID_Usage(HID_USAGE_GENERIC_KEYBOARD),
  HID_Collection(HID_Application),
    HID_UsagePage(HID_USAGE_PAGE_KEYBOARD),
    HID_UsageMin(224),
    HID_UsageMax(231),
    HID_LogicalMin(0),
    HID_LogicalMax(1),
    HID_ReportSize(1),
    HID_ReportCount(8),
    HID_Input(HID_Data | HID_Variable | HID_Absolute),
    HID_ReportCount(1),
    HID_ReportSize(8),
    HID_Input(HID_Constant),
    HID_ReportCount(8),
    HID_ReportSize(1),
    HID_UsagePage(HID_USAGE_PAGE_LED),
    HID_UsageMin(1),
    HID_UsageMax(8),
    HID_Output(HID_Data | HID_Variable | HID_Absolute),
    HID_UsagePage(HID_USAGE_PAGE_KEYBOARD),
    HID_UsageMin(0),
    HID_UsageMax(101),
    HID_LogicalMin(0),
    HID_LogicalMax(101),
    HID_ReportSize(8),
    HID_ReportCount(6),
    HID_Input(HID_Data | HID_Array),
  HID_EndCollection,
};

Dear Tsuneo,

Thanks so much for your guidance! I have my PC detects MCB2140 as a USB keyboard and play arround with 2 bytes report in, one for modify keys one for array keys. But I still have one stupid question, need your help!!

Actually, in HID1_11.pdf, there is a report example for a standard keyboard, which the report data is 8 bytes format(1 modify keys, 1 reserve, 6 for array keys). And I see that Windows only has the maximum number of combined keys is 3 or 4, ex: CTRL+ALT+DEL, so I wonder why the standard keyboard has the report in data format is 8, is it redundant??

Please help me clear!
Tuong Nguyen

I don't know if this is relevant to USB but a key press in Windows can use any number of modifiers.

CTRL+ALT+DEL is just the single key DEL with CTRL and ALT as modifiers.

But the next issue is that a keyboard can handle n-key rollover, in which it keeps track of n concurrently pressed characters, and then reports the key releases first when you do release any of the n pressed keys.

So in a game, you may press one key to move forward, while pressing another to slide sideways, while pressing a third key to fire a weapon and potentially a fourth key to aim through a sniper scope. For a gamer, it is important to select a good keyboard that supports a large "n", so it is able to keep track of many concurrently pressed keys.

> so I wonder why the standard keyboard has the report in data format is 8, is it redundant??

Keyboard puts an input report which shows the current status of all keys (snapshot) - not just the key which makes or breaks. Keyboard puts input reports regularly, or just at the timing when any key-down/-up occurs (*1). In either case, the input report is a snapshot of all keys.

The format of the standard input report for keyboard is as follows,

Byte
  0   Modifier keys     bitmap of left and right CTRL, SHIFT, ALT, GUI keys
  1   Reserved
  2   Keycode array[0]  6 byte keycode array for the keys other than modifier
  3   Keycode array[1]
  4   Keycode array[2]
  5   Keycode array[3]
  6   Keycode array[4]
  7   Keycode array[5]

The Modifier keys field holds the ON/OFF status of the modifier keys on each bit, just when the report is made. The Keycode array lists up only the keys which are currently ON, up to six keys - 6-keys rollover (*2).

Comparing the last report and new one, HID host knows make/break of keys.
If a keycode appears in the new report, but not in the last one, the key makes.
If a keycode is shown again in the new report, the key is still pressed.
If a keycode disappears in the new report, the key is released.

Thanking to this format, shooting games on your PC is able to move the hero diagonally, when you push the up and left cursor keys at the same time. Also you can fire while you are moving :-)

I don't know why a reserved byte is there between the modifier and the array. Maybe, they thought more modifier keys may be equipped in future.

(*1) chosen by SET_IDLE requests
(*2) Increasing the array size on the report descriptor, input report can hold more keys. For example, 100-keys rollover :-)

Tsuneo