I've read some parts of the Qt 5.10 Bluetooth documentation and follow the Scan tutorial to discover the services, characteristics and descriptors of my device.
It works nice but I need to wait few seconds between each interaction (like, move into a service to list every characteristics).
My question is, can I directly access to a descriptor or a characteristic to write/read directly the data ? And how ?
I have static addresses and I will always use them on every bluetooth devices. I need to write just with the Service/Characteristic/Descriptor combination.
On Ionic, I'm doing it with the Cordova BluetoothLE Plugin and it works fine.
Can anyone help me ? Thank you very much !
Related
I'm right now reading the microsoft documentation about drivers and core audio apis. At the moment I'm still confuse which way to go to achieve what I need.
I have an audio application which is Standalone and coded with framework JUCE in C++. And I need to build a Windows solution that would capture the audio stream that is going to an audio endpoint device to use it as an input of my audio application.
This stream must have an unaltered volume: always 1.0 (no matter if the hardware volume is changed or muted).
I must be able to choose between the different endpoint devices, for exemple if I have an external soundcard that is plugged, my audio application should be able to intercept and copy the stream that is going to that external soundcard, or do the same for the stream that is going to the built-in speakers.
The idea is to capture the output streams before they are modified by hardware volume modifications, and make a copy of them routed to my application without changing the output routing and behaviour.
The microsoft documentation is very furnished, but even if the WASAPI provides a lot of ways to capture and stream from audio endpoint devices, I'm not sure it is possible to get an unaltered volume, as it will always capture what's exactly coming out of the speakers.
This is why I don't know If I can implement a feature directly in my audio application that will get the streams I want with WASAPIs or if I have to code a proper Audio Driver that would make a copy of the streams I want for my application to be able to use these streams.
The documentations I refer to:
Audio Drivers design guide
Core Audio APIs / WASAPI
Thanks for the help,
Best,
Maxime
Sometimes the volume control is implemented in software, and sometimes it is implemented in hardware. You can call IAudioEndpointVolume::QueryHardwareSupport to see if the volume control for the audio endpoint you're working with is implemented in hardware or software.
Sometimes the audio loopback is implemented in software, and sometimes it is implemented in hardware. There is no API to tell which.
If the audio loopback is implemented in software, and the volume control is implemented in hardware, then you will get back the data you want.
If the audio loopback is implemented in hardware, or the volume control is implemented in software, the the audio data you get back has already had the volume adjustment applied.
What does your application do with the audio data it receives? The primary use case for audio loopback data is echo cancelation, where you usually WANT the volume to be applied.
I am trying to implement a C++ code (using bluez 5.43 and dbus) to read advertisement packets from a BLE sensor. As per the bluez DBus docs, there is a StartDiscovery API that can be used to scan for nearby devices. However, I am unable to find any APIs to store/parse the advertisement packets from nearby BLE devices. The advertising-api.txt lists registeradvertisement API but as per my understanding, it can be used only for creating advertisement packets and not reading from an external device (or am I wrong?) Can someone please guide me on the correct way to get advertisement packets from nearby BLE devices using bluez and DBus?
Thanks for the suggestions everyone. I was finally able to get the manufacturer data by using Intel's tinyb library. It has an enable_manufacturer_data_notifications API which enables you to be notified whenever the manufacturer data changes.
The behavior you described in one your last comment is the right one (the advertising data is not beeing updated) : if I am correct a BLE device is not supposed to be up all the time, it can sleep or turn to low-power etc.
In this context, it is not weird that the data is in some way "cached". From my experience, when you perform a scan and discover a device (even if you don't Connect to it), the device information will be stored for some time.
In your case, that's problematic because you are passing data through the advertising. However there is a way to force bluez to remove all it's cached data about a device :
the adapter-api provides a RemoveDevice(object device) method. It takes the object path (eg "/org/bluez/hci0/dev_AA_BB_AA_BB_AA") as argument.
If you're looking for DBus bindings in C, I suggest GLib GDBus (you will find links at the bottom of this tutorial on freedesktop website : https://dbus.freedesktop.org/doc/dbus-tutorial.html).
If you are familiar with bluetoothctl (a tool to interact with bluez using commands), it was developped by the bluez guys using Glib GDbus and you can find the source code here (look at the bottom to find the command list) : https://git.kernel.org/cgit/bluetooth/bluez.git/tree/client/main.c
There are more straigthforward ways to use GDBus with bluez but bluetoothctl source code is a start and you'll find examples for pretty much anything that is possible to do with bluez =)
I am developing C++/Qt application which interacts with Tektronix TDS2002 oscilloscope via USB. The oscilloscope appears as "USB Test and Measurement device (IVI)".
Currently I use TekVISA library supplied by the oscilloscope's vendor. It works, but it is huge, old, buggy and poorly maintained. Therefore I would like to bypass the library and interface the device directly.
So far I have found this simple library: https://github.com/xyphro/WinUsbTmc It is exactly what I am looking for, but it uses libusb which requires to install some device filter and in addition it is advised to be more development tool than customer solution. Do you have any experience on this?
What is the easiest way to interact with USB Test and Measurement device in Windows/C++/Qt?
Thank you for your suggestions :)
You need a USB driver. My oscilloscope works with the driver included in this VISA package (the driver can be extracted very easily): http://www.keysight.com/main/software.jspx?cc=CZ&lc=eng&nid=-11143.0.00&id=2504667&pageMode=CV I assume all USB TMC devices can use the same driver, but I have no possibility to check this.
USB driver can be accessed via standard Windows functions. Guys on this forum were really close:
https://forum.tek.com/viewtopic.php?f=568&t=137573 and also this document was very useful: http://www.ivifoundation.org/downloads/Class%20Specifications/Ivi-6%202_USBTMC_2010-03-23.doc
You cannot write commands to OSC directly - data you send and receive have certain header which has to be in the correct format, otherwise the oscilloscope ignores the message. See reading and writting implementation in this simple library: https://github.com/xyphro/WinUsbTmc I didn't use this library because it uses libusb library which uses some kind of device filter and I personally do not like this concept (and in addition I have genuine working driver).
Data you read have also a simple header. To ensure you fit the header structure on input data well, you should first flush the input buffer. Then you issue reading request (using write command - see WinUsbTmc library above) and finally you receive the data and fit the header on its beginning.
I hope this will help to somebody :)
With regards
klasyc
How do I most properly use libusb to talk to connected USB devices?
Specifically, how do I transfer data to the USB devices, receive information from the devices, find out the name of the connected device, if they have storage, etc.
More specifically, I will be running this on a Mac OS X machine, so I know I can't just use Windows header files.
If there is a good explanation on libusb and USB devices, that would be helpful too.
Here is a post on a similar question that might be useful to you. I include plenty of links.
But maybe you'd rather see it here. So in that case, here it goes!
Libusb allows you to enumerate devices and select the one you want based on a specific Vendor/Product id (V/P Id). If you don't know this and can't find it online with the product's description then you can easily find it.
If it is not online you will need to use an app similar to lsusb on Linux. (I don't believe it is on Mac.) When you run lsusb it lists connected devices and their V/P Ids. You can easily find your device by unplugging, running lsusb, and plugging the device back in and comparing. It's a piece of cake. Any usb list app on Mac will hopefully display the V/P ID like lsusb does.
Then once you have this V/P ID you will use libusb (if using 0.1) to enumerate all devices and find the device that matches that id. (I support using libusbx which happens to have a single find device function based on V/P id - in fact, libusbx is a whole lot more concise all around.)
After selecting your device you will send a packet using either Feature or Output Reports. This is the most complicated part because the packet you send is dependent on the individual device I believe. It is 8 bytes of data and only one of which is a single character you wish to send to the usb device. (If you wanted to send 8 characters, you would have to loop through an array of chars and send a feature or output report for each character.)
As an example feel free to reference a rather specific terminal example I wrote for controlling two LEDS. If it's helpful, great! It contains a libusbx and libusb-0.1 example.
I hope this helps!
The official site for libusb 1.0 (the newer and recommended version) is https://libusb.info/. The API documentation is at http://api.libusb.info. Click on the Modules section to walk through the different function areas. The source is at https://github.com/libusb/libusb and you can see some working examples at https://github.com/libusb/libusb/tree/master/examples. Hope that helps!
The article from #user2469202 is a good basic intro also.
The process that you can follow is:
Get the VID, PID for the device that you want to communicate using lsusb
Try to open the device and read the device descriptor
If you want name of the device use string descriptor to get that
Check if any kernel driver is attached. If it is, then detach it and do some raw data transfer
After getting the response again re-attach the driver.
has anyone some kind of documentation how to implement an own flashing-procedure for an atmega8-microcontroller ?
when searching, i have only found tutorials, on how to flash custom software with the normal flashing-software (in most cases atmels flip), but i haven´t found any documentation, how you would implement it in your own software. eg. what are the commands in which timings and with which responses from the microcontroller.
so, thank you in advance
You program the chip by communicating with it through SPI lines while it is in reset. You can find details in the chip's datasheet.
You can't do that directly from your PC, you need to have an external hardware device (even if it is a mere level converter connected to your serial/parallel port). How you communicate with that device depends on the device.
If you want to implement bootloader functionality, you should take a look at boot_page_write() function in avr-gcc help. Basically what you need is the data stream from PC/other uC which will accumulate in RAM until you have enough to write one page.
You can search for AVR Universal Boot loader for example how it can be implemented.