Get the battery voltage of Logitech Lightspeed device with IOKit? - swift

Question

I'd like to write a simple tool in Swift to read battery status of my mouse (Logitech G Pro Wireless). Since it's my first dive into both IOKit and managing HID devices, I am struggling with getting it done.
Here's my current approach:
I used this library to skip for now messing with Obj-C https://github.com/Arti3DPlayer/USBDeviceSwift
On launch of the app I create HID Device with hardcoded ids and start listening for its presence:
struct MyApp: App {
let rfDeviceMonitor = HIDDeviceMonitor([
HIDMonitorData(vendorId: 0x046d, productId: 0xC539)//0xc088)
], reportSize: 64)
var body: some Scene {
Window()
.onAppear {
let rfDeviceDaemon = Thread(target: self.rfDeviceMonitor, selector:#selector(self.rfDeviceMonitor.start), object: nil)
rfDeviceDaemon.start()
}
}
}
Another class is listening for connection and device's data.
func configure() {
NotificationCenter.default.addObserver(self, selector: #selector(self.usbConnected), name: .HIDDeviceConnected, object: nil)
NotificationCenter.default.addObserver(self, selector: #selector(self.hidReadData), name: .HIDDeviceDataReceived, object: nil)
}
#objc func usbConnected(notification: NSNotification) {
guard let nobj = notification.object as? NSDictionary else {
return
}
guard let deviceInfo: HIDDevice = nobj["device"] as? HIDDevice else {
return
}
self.deviceInfo = deviceInfo
write()
}
#objc func hidReadData(notification: Notification) {
let obj = notification.object as! NSDictionary
let data = obj["data"] as! Data
print([UInt8](data))
}
func write() {
let payload: [UInt8] = [
0x10, // short message
0xff, // receiver's index
0x06, // feature index - battery voltage for g pro wireless
0x00,
0x00,
0x00
]
var correctData = Data(payload)
var count = correctData.count
let ret: Int32 = IOHIDDeviceGetReport(
self.deviceInfo.device,
kIOHIDReportTypeFeature,
CFIndex(0x10),
&correctData,
&count
)
print(ret) // 0xe0005000
print([UInt8](correctData)) // [16, 255, 6, 0, 0, 0]
}
The issue is that IOKit always returns a value (0xe0005000) after calling IOHIDDeviceGetReport that is not a success. I have no idea what this means, since kIOReturn header doesn't mention this value at all.
Links that I found useful:
receiver's properties: https://github.com/pwr-Solaar/Solaar/blob/78341f87e969fcdb657d912953f919e7bdd7c491/docs/devices/Lightspeed%20Receiver%20C539.txt
Mouse's properties: https://github.com/pwr-Solaar/Solaar/blob/78341f87e969fcdb657d912953f919e7bdd7c491/docs/devices/G%20Pro%20Wireless%20Gaming%20Mouse%204079.txt
feature's and implementation of reading features via hidpp 2.0 https://github.com/pwr-Solaar/Solaar/blob/eac916b57c78b23a40bcded1a9c89e2cc30e06d4/lib/logitech_receiver/hidpp20.py
Logitech's specification's draft for hidpp 2.0 https://drive.google.com/drive/folders/0BxbRzx7vEV7eWmgwazJ3NUFfQ28?resourcekey=0-dQ-Lx1FORQl0KAdOHQaE1A
The most important informations I got from these sites:
My mouse has only a feature of passing current voltage. It's available on index 6. Also, there's mentioned hex value of 0x1001 next to that feature, but I am not sure what it could mean, maybe it's some Logitech's identifier for this feature.
buffer size has 7 or 20 bytes (this call should be 7B), where:
first means message size (short - 7B - 0x10, long - 20B - 0x11)
second is device index (0xFF is for receiver, yet to find which is meant for device connected via a wire)
Third means feature index (which is 6 in this case)
Fourth is divided on function and software identifier (in this order). The second one people say that is used to recognize responses meant for us from the rest of the output.
rest should be filled by report that I'd like to get.
https://github.com/pwr-Solaar/Solaar/blob/d41c60718876957158f2ef7ce51648cab78c72ad/lib/logitech_receiver/base.py#L437 - here's Python's implementation of sending such a request. This line particularly looks like it sends a request, then it waits for a message back? This is the point where I am struggling the most.
There's a line in documentation that describes bytes meaning, says:
"The device index, feature index, function identifier, and software identifier are always returned unchanged.", so I suppose I should use getReport instead of setReport, but again, my knowledge is very limited here, so I tried setReport as well, but with no luck. Same error has been thrown.