Detect power change event / UPS state

[Cobra91151]

Hi! I want to detect when the system is on UPS or just power state changes.

Something like this:

I tried to detect it using GetSystemPowerStatus function:

Code:

    SYSTEM_POWER_STATUS powerStatus;
    bool powerStatusRes = GetSystemPowerStatus(&powerStatus);

    switch (powerStatus.ACLineStatus) {
        case 0:
            std::cout << "Offline" << std::endl;
            break;
        case 1:
            std::cout << "Online" << std::endl;
            break;
        case 255:
            std::cout << "Unknown status" << std::endl;
        default:
            std::cout << "Failed to detect the status" << std::endl;
    }

    switch (powerStatus.BatteryFlag) {
        case 1:
            std::cout << "High — the battery capacity is at more than 66 percent" << std::endl;
            break;
        case 2:
            std::cout << "Low — the battery capacity is at less than 33 percent" << std::endl;
            break;
        case 4:
            std::cout << "Critical — the battery capacity is at less than five percent" << std::endl;
            break;
        case 8:
            std::cout << "Charging" << std::endl;
            break;
        case 128:
            std::cout << "No system battery" << std::endl;
            break;
        case 255:
            std::cout << "Unknown status—unable to read the battery flag information" << std::endl;
            break;
        default:
            std::cout << "Failed to detect the battery flag" << std::endl;
    }

But it returns powerStatus.ACLineStatus for UPS or AC as Online and for powerStatus.BatteryFlag - No system battery.

Also I have tried to detect the UPS using GetPwrCapabilities function:

Code:

SYSTEM_POWER_CAPABILITIES SysPowerCapabilities = {0};

if (!GetPwrCapabilities(&SysPowerCapabilities)){
    std::cout << "Failed to get System Power information!" << std::endl;
}

if (SysPowerCapabilities.UpsPresent) {
    std::cout << "UPS found" << std::endl;
} else {
    std::cout << "UPS not found" << std::endl;
}

It returns - UPS not found (driver is not available for this UPS model).

Now I'm trying to detect power changes by using the Qt nativeEvent function:

bool Test::nativeEvent(const QByteArray &eventType, void *message, long *result)
{
    Q_UNUSED(result);
    Q_UNUSED(eventType);
    MSG *msg = static_cast<MSG*>(message);

    if (msg->message == WM_POWERBROADCAST && msg->wParam == PBT_APMPOWERSTATUSCHANGE) {
        qDebug() << "Power changed!!!";
    }

    return false;
}

But nothing is printed to the console. Any ideas how to detect it? Thanks.

[SGaist]

Hi,

If I understand correctly, you don't have the driver for your UPS. How can you expect Qt to catch any related events if your system can't handle the hardware ?

[Cobra91151]

@SGaist

Yes, I don't have the driver for this UPS. So how other apps, for example ViewPower communicate with this UPS? Thanks.

[aha_1980]

@Cobra91151

The best would be to ask the authors of ViewPower for that ;)

[SGaist]

There are likely generic APIs that the device has to answer to. Like you already did. They may be doing some polling.

[Cobra91151]

@SGaist

By enumerating all usb devices I got the Vendor and Product ID for the UPS. How about talking to the serial port, for example using QSerialPort class?

[Cobra91151]

@aha_1980

Great idea, but this project is deprecated.

[aha_1980]

@Cobra91151 so now you need to find the documentation for the UPS. It should explain how to control it.

[Cobra91151]

@aha_1980

No tech. documentation is available for this UPS. But I got some values from the net:

 0x00840010 = UPS
 0x00840012 = Battery
 0x00840030 = Voltage
 0x00840040 = ConfigVoltage
 0x0084001a = Input
 0x0084005a = AudibleAlarmControl
 0x00840002 = PresentStatus
 0x00850044 = Charging
 0x00850045 = Discharging
 0x008500d0 = ACPresent

But these values could be different for my UPS model.

Also I succeeded with connecting to the UPS usb:

Code:

    QString devicePath = "\\\\?\\HID#VID_....";
    HANDLE fileHandle = CreateFileA(devicePath.toStdString().c_str(), GENERIC_READ, FILE_SHARE_READ, NULL, OPEN_EXISTING, FILE_FLAG_OVERLAPPED, NULL);

    if (fileHandle != INVALID_HANDLE_VALUE) {
        std::cout << "Success. Device opened for reading..." << std::endl;
        OVERLAPPED overlapped = {};
        uint8_t readBuffer[1024];
        BOOL readDeviceRes = ReadFileEx(fileHandle, (LPVOID)readBuffer, sizeof(readBuffer), &overlapped, readCompleted);

        if (readDeviceRes) {
            std::cout << "Success..." << std::endl;
        } else {
            std::cout << "Failed..." << std::endl;
        }
    } else {
        std::cout << "Failed to open device for reading!" << std::endl;
    }

    CloseHandle(fileHandle);

void CALLBACK readCompleted(DWORD dwErrorCode, DWORD dwNumberOfBytesTransfered, LPOVERLAPPED lpOverlapped)
{
    std::cout << "Test... " << dwNumberOfBytesTransfered << std::endl;
}

When I start the app, it displays:

Success. Device opened for reading...
Success...

But ViewPower app displays that UPS connection has been lost, when I close my app, then the UPS connection has been established. This means that they also read the UPS data from a USB. Now I need to figure out how to get these values, read bytes.

[Cobra91151]

I have found that I need to use the HID API to get some values for the UPS.

Updated code:

   QString devicePath = "\\\\?\\HID#VID_....";
   HANDLE fileHandle = CreateFileA(devicePath.toStdString().c_str(), GENERIC_READ, FILE_SHARE_READ, NULL, OPEN_EXISTING, FILE_FLAG_OVERLAPPED, NULL);

   if (fileHandle != INVALID_HANDLE_VALUE) {
       std::cout << "Success. Device opened for reading..." << std::endl;
       PHIDP_PREPARSED_DATA preparsedData;
       HIDP_CAPS capabilities;
       HIDD_ATTRIBUTES attributes;
       BOOL hidPreparsedRes = HidD_GetPreparsedData(fileHandle, &preparsedData);

       if (hidPreparsedRes) {
           if (HidD_GetAttributes(fileHandle, &attributes)) {
               std::cout << "Product ID: " << attributes.ProductID << std::endl;
               std::cout << "Size: " << attributes.Size << std::endl;
               std::cout << "Vendor ID: " << attributes.VendorID << std::endl;
               std::cout << "Version number: " << attributes.VersionNumber << std::endl;

              if (HidP_GetCaps(preparsedData, &capabilities) == HIDP_STATUS_SUCCESS) {
                  std::cout << "Caps: " << capabilities.NumberOutputValueCaps << std::endl;
              } else {
                  std::cout << "Failed to return HID capabilities!" << std::endl;
              }
           } else {
              std::cout << "Failed to get HID attributes" << std::endl;
           }

           std::cout << getLastErrorAsString() << std::endl;
       } else {
           std::cout << "Failed to get preparsed data!" << std::endl;
       }

       HidD_FreePreparsedData(preparsedData);
   } else {
       std::cout << "Failed to open device for reading!" << std::endl;
   }

   CloseHandle(fileHandle);

So now, it returns:

Success. Device opened for reading...
Product ID: 20833
Size: 12
Vendor ID: 1637
Version number: 2
Caps: 1

HIDP_CAPS structure has a lot of different values, the question is how to convert them to UPS values to check for power changes/UPS status? Thanks.