I have two programs (MS VC++) which using multicast - receiver and sender. I test it between desktop PC (Windows 7) and netbook (Windows XP) via WiFi. Desktop PC have WiFi dongle which working in AP mode. If I specify INADDR_ANY in the interface address in the sender program, I get a problem: multicast doesn't reach netbook from desktop PC. If I specify real address of this WiFi interface instead INADDR_ANY - it working fine.
So, I want that my sender program can working on all interfaces. How I can to do that? I have to initialize separate socket for each interface? Or may be it have more elegant possibility?
As previous people said, you have to select your output interface explicitly. If you want to multicast onto different interfaces concurrently, you'll need multiple sockets. In boost::asio, the corresponding call is:
boost::asio::ip::udp::socket* _write;
...
_write->set_option( ip::multicast::outbound_interface( ifAddr.to_v4()));
Related
I have a Wemos D1 Mini (ESP8266), flashed with WLED and I want to create an application like .exe and have control on turning it on/off and choose colors. Does anyone have any idea how I can do without to connect on wifi and just do everything via USB?
To control the WLED firmware over USB, you would use the firmware's ability to be controlled over a serial connection. It looks like you would open the virtual serial port that appears when you plug in the device, at a speed of 115200, and then you take the same JSON that you would POST to /json/state for controlling it over WiFi, and instead send it over the serial connection, and get your responses back over the serial connection.
You could also implement the TPM2 protocol, or the Adalight protocol (which doesn't really seem to be documented except in code), as those are also supposed to be supported.
If you want to do all this in C++ on Windows, you might start by reading the (very old) Windows tutorials for Win32 API serial port programming. If you only want to target Win10 or newer, you could learn C++/WinRT and then use the new WinRT serial APIs. Or you could consult the answers to this question about serial programming on Windows.
I'm quite new to programming at linux and its file-based communication.
I need to create a virtual modem (or modem emulator) at linux machine. The idea is that the software module that sends commands to hardware modem on an FPGA,
At FPGA:
SoftwareModule <= ttyACM => HardwareModem
What I need to achieve at my computer:
SoftwareModule <=> MyModemEmulator acting like a fake UART
Purpose is that the software module can be tested on a linux machine where I have a fake software modem UART(?) port. So the software module sends the modem commands and my fake modem module catches and responds accordingly. So my module will be actually acting like a hardware modem.
What could be the steps I need to take for that? I'm quite new to working with serial ports and don't have deep knowledge of linux or hardware stuff.
I have come across 'socat' but I'm not sure if that can really serve the purpose.
So far I have only learned how to create a basic file system with FUSE (as it was suggested by someone), but I'm not sure how can I use it for my purpose. I'm not looking for a proprietary solution, and not looking for windows based solution either.
Please guide me to the right directions.
Thank you !
Creating a Fake Serial Port to Emulate Modem
What you refer to as a "serial port" in Linux is actually a serial terminal with many software layers.
Study Linux serial drivers, and the termios man page for salient functions that need to be emulated.
And you have not even considered how to factor in the USB component of the communication path.
At FPGA:
SoftwareModule <= ttyACM => HardwareModem
...
My computer with ubuntu does not have ttyACM
A /dev/ttyACMx device node is only created when a USB serial gadget is connected to the host.
So it's not surprising that you cannot find such a device node.
What I need to achieve at my computer:
SoftwareModule <=> MyModemEmulator acting like a fake UART
You have stated the issue poorly, since you (misguidedly) think that a "fake UART" (integrated with your "MyModemEmulator") is the appropriate solution.
Do not try to emulate both a serial terminal and an external modem on the Ubuntu host, since you are "quite new to programming at linux and serial ports" and the task of accurately emulating a serial terminal is risky and expensive.
What your goal should be is:
SoftwareModule <= ? => MyModemEmulator
and the question is "what is needed in the middle to interface these two units?".
IOW you have posted an XY problem.
There are a plethora of SBCs (single board computer) that have a USB gadget port and can be configured as a USB serial gadget that uses CDC ACM.
Since the actual "hardware modem on an FPGA" will use a USB CDC ACM connection, you should consider using an actual /dev/ttyACMx serial terminal, and emulating just the external device ("hardware modem") with a SBC.
In other words, instead of trying to achieve:
SoftwareModule <=> MyModemEmulator + fake USB serial terminal
it should be much easier to use existing interfaces and implement:
SoftwareModule <= USB => emulated HardwareModem
with a SBC running your Linux application for modem emulation using /dev/ttyGS0 (a USB serial terminal on the gadget end).
By using an actual USB CDC ACM connection and not implementing the "fake USB serial terminal", this approach eliminates an entire layer of SW+HW emulation and its possible false test results.
Addendum
If the use and/or cost of embedded Linux on a SBC concerns you, then there is an alternative scheme to emulate the "hardware modem" on your Ubuntu PC host instead of the SBC using a USB-to-RS232-to-USB connection.
Acquire a pair (i.e. quantity 2) of USB-to-RS232 adapters and a (very short) null-modem cable.
Connect the DB-9 ends of the adapters to the null-modem cable to make a single cable with both ends having a USB male type-A connector.
Plug one adapter into the PC to create the /dev/ttyUSB0 device node. Treat this as the equivalent to /dev/ttyACM0 for your SoftwareModule.
Plug the other adapter into the PC to create the /dev/ttyUSB1 device node. Treat this as the equivalent to /dev/ttyGS0 for your emulated "hardware modem".
Develop, execute, and debug your emulated "hardware modem" on the Ubuntu PC host (without the unnecessary task of "creating a fake serial port").
Currently I want to create a qt application on my Desktop that say, has 3 buttons. These 3 buttons can change certain variables for my device, which will be connected to the desktop with a microcontroller.
I want my desktop application to be able to communicate with the microcontroller. For example, clicking a button might flip a certain boolean variable and the microcontroller will adjust accordingly.
I have no idea how to start and what sort of questions I should be asking and how to tackle this at a high level.
Thank you.
My desktop is a macbook pro retina 15-inch 2014 and my microcontroller is either an Teensy, or an Intel Atom.
I don't know what type of microcontroller you are using, but if it has support for UART you can use the QSerialPort lib (http://doc.qt.io/qt-5/qserialport.html) to send data using a serial port.
In case of an arduino, you can send messages using this lib directly via the USB emulated COM port. If it don't have USB emulated COM port, you should use a serial adapter (an Arduino board can play this role).
The first thing to look at is what communication buses are common between your desktop computer and your microcontroller. Does your microcontroller have USB or ethernet capabilities? Does your microcontroller have expansion boards for WiFi or bluetooth support? Do you have access to an I2C bus in your desktop PC?
Depending on the answers above, if your microcontroller and your computer do not share common communication buses, you might have to use intermediary hardware, for instance, you might want to use something like the FTDI USB (on your desktop) to UART (for the microcontroller) cables, you can find those here: http://www.ftdichip.com/Products/Cables/USBTTLSerial.htm
In that case I'd recommend using a cable with VCD drivers, so the cable appears as a Serial port to your computer, which you can access in QT by using QSerialPort (http://doc.qt.io/qt-5/qserialport.html)
There would be other similar solutions, but I'd say that, if there are no shared buses between your microcontroller and host, this would be one of the most universal. Maybe if you specify your microcontroller or embedded board We could help a little more.
I'm trying to write a program that sends COM port information to devices that may get unplugged and end up with a different COM port number. Using SetupDi, I know it's possible to list all the COM ports on a computer by number, but given that the number might change I'm trying to find a better way to access the COM ports.
The COM devices I'm using are FTDI serial-to-com adapters that let me program the device model. I'd love to be able to choose a COM port based on the device model. I've tried (almost) all of the properties that I can get to using SetupDi, but no dice. It looks like there's a difference between the device list SetupDi lets me access, and the devices that show up under Devices and Printers (where the model name does show up). Is there any way to get devices in the Devices and Printers window programmatically and map them to COM port using Windows APIs?
The link below is a great (if not the only) comprehensive overview on how to enumerate COM ports on Windows and extract extra information in various ways:
http://www.naughter.com/enumser.html
What we use in our own software (Docklight) is according to what the "UsingSetupAPI1" way from the enumser.cpp file shows (SetupAPI - GUID_DEVINTERFACE_COMPORT). The UsingSetupAPI1 example demonstrates how to extract the device name as shown in the Windows Device Manager, along with the COM number. This is called "friendlyNames" in the enumser.cpp code.
Another way to identify and communicating to your device could be not asking Windows in the first place, but the FTDI D2XX API:
http://www.ftdichip.com/Support/SoftwareExamples/CodeExamples.htm
We use the D2XX API for communication when we know it is always a FTDI device. Identification is simpler and we have much better performance / less latency than using Windows Communications API via "virtual COM port".
If we need to correlate between COM port numbers and a FTDI device ID, we use the FTDI D2XX API's ListDevices and GetComPortNumber functions.
Is it possible to read/write from/to a specific USB port, avoiding all that USB handshaking stuff?
What I want to do is communicate with a microcontroller, for example, that doesn't have a USB driver on board via USB. I want my C++ application to be able to send data via a specific USB port and then to receive data from that same USB port.
Basically what I want to be able to do is treat that USB port like a serial port. Is this possible? Is there a workaround I can use?
Thanks in advance.
PS: I know this isn't the best way to go about communication with a uC, but let's assume, for some reason, I have to do it this way.
Edit: BTW I'm using Windows 7
The usual solution is to use an FTDI USB-to-serial chip, such as the FT232R, on your microcontroller board. Then, as far as your MCU is concerned, it's talking to a serial port, and on the host machine you just have to have the right drivers.
On my Mac, the FTDI chip shows up as a serial port at /dev/tty.usbmodem____, where ____ is some persistent unique ID assigned by the Mac on first detection. Unplugging and replugging, even weeks later, gets the same number, but it's a different number on a different Mac.
On Windows, it shows up as a new COM port if you have the drivers installed, IIRC. On Linux, it shows up as /dev/ttyUSB_ where _ is a serial number starting at 0, if you have FTDI serial driver support enabled in the kernel. This can get tricky if you plug in more than one FTDI chip.
If your microcontroller has a built-in USB port, then you need to find the software for it to identify itself as a standard CDC (Communication Device Class) serial port device (standard documentation available). Most OSs have support for this standard USB device class.
Use one of the USB to serial port adapters. The USB port will look just like a serial port to your C++ program.
In general you can do a close approximation of this using the HID interface: drivers are built in, and you can send feature reports in both directions. It isn't quite serial port simplicity (since it is packets, as opposed to a continuous byte stream) but hidapi makes it really simple and cross-platform.