CODEWITHSUNDEEP
cwinapi
user657267
user657267

Reputation: 21000

Raw input winapi in c, can't get device info

I'm messing around with a USB RFID scanner and trying to read input with raw input, so far I have this

#define _WIN32_WINNT 0x0601
#include <windows.h>
#include <stdio.h>

int main(void)
{
    PRAWINPUTDEVICELIST pRawInputDeviceList;
    PUINT puiNumDevices, pcbSize;
    UINT cbSize = sizeof(RAWINPUTDEVICELIST);
    char *pData[1000];

    GetRawInputDeviceList(NULL, puiNumDevices, cbSize);    
    pRawInputDeviceList = malloc(cbSize * *puiNumDevices);   
    GetRawInputDeviceList(pRawInputDeviceList, puiNumDevices, cbSize);

    // gives a correct RIM_TYPE for all devices 0-7 (GetRawInputDeviceList returns 8 devices for me)
    printf("%I32u\n", pRawInputDeviceList[0].dwType); 


    GetRawInputDeviceInfo(pRawInputDeviceList[1].hDevice, RIDI_DEVICENAME, pData, pcbSize);

    // gives a huge number (garbage?), should be the length of the name
    printf("%u\n", pcbSize);        

    // "E" in my case
    printf("%s\n", pData);

    // error 87, apparently ERROR_INVALID_PARAMETER
    printf("%I32u\n", GetLastError()); 

    return 0;

}

Upvotes: 0

Views: 1368

Answers (2)

dappawit
dappawit

Reputation: 12570

When you call GetRawInputDeviceInfo, it expects pcbSize to be a pointer. You have it as a pointer, but its not pointing to anything. Try this:

  1. Get rid of pcbSize (everywhere).
  2. Create a variable UINT cbDataSize = 1000. This is the size of your pData array.
  3. For the last argument of GetRawInputDeviceInfo, use &cbDataSize. This takes the address of cbDataSize, the address is a pointer.
  4. Change printf("%u\n", pcbSize); to printf("%u\n", cbDataSize);.

See how that works for you.

[edit]

Also, you should do the same thing for puiNumDevices. Instead, create a UINT called uiNumDevices. Use &uiNumDevices where the functions expect pointers.

Upvotes: 1

Lynn Crumbling
Lynn Crumbling

Reputation: 13357

I am going to go out on a limb here and guess that this thing may actually be a HID device. Do you know if it is?

HID Devices are actually pretty easy to talk to; you connect to them via CreateFile() -- the same way that you would open a COM port -- and then just ReadFile() to get data.

Most of the problem is figuring out the correct path to connect to. It's actually a value called DevicePath that you get from SetupDiGetDeviceInterfaceDetail().

A rough map of it looks like this:

HidD_GetHidGuid() to get the HID guid
SetupDiGetClassDevs() to get the list of dev
Looping through devs, until you find yours:

  • SetupDiEnumDeviceInterfaces() to enum the device interfaces
  • SetupDiGetDeviceInterfaceDetail() to get the detail
  • CreateFile() to open the device with the DevicePath from the detail.
  • HidD_GetAttributes to get the vendorid and productid to see if it's your device.

If it is, remember it, and use ReadFile() to get data.

Upvotes: 0

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