I'm trying to learn how to write C code that will read from the serial port in Linux. I've found what seems to be a good tutorial here.
I want to be able to test this code, so I think I need either a serial port, or a way to write to the serial port while the code from above is reading.
I'm running Ubuntu 10.04 as a virtual machine on my Mac using virtualbox. My idea was to set up a virtual serial connection and write from the host to the guest. Hopefully something as simple as cat "Hello World" > /tmp/fake_serial in a host terminal, and for that to be read by the program in the link above.
Is this possible? I've tried adding a serial port using virtual box and when I try to do the above command I get an error saying I can't write to a socket.
The second option I thought of was using something like minicom inside the guest OS, to connect to say /dev/ttyS1 and write messages for my code to read at the same time. Again, assuming that the baud rates and other settings are OK, would this be possible?
I don't have a lot of experience working with serial ports, so I'd appreciate any suggestions about the best way to do this. Thanks in advance.
So to get this working I just added another Ubuntu VM on VirtualBox, and connected the two together via a virtual serial port. My main, original VM, which I use for a lot of developing will be referred to as VM1. The new VM, with a small hardrive that will only be used for sending messages to VM1 will be called VM2. These are both Ubuntu 10.04 VMs.
In VirtualBox go to Settings for VM1, go to ports, and change the settings as follows:
Now go to VM2, and select settings, ports, then change as follows:
Now first you need to start VM1. When that's booted then boot VM2. Now you can open a terminal in VM1, and type screen /dev/ttyS0 38400 (you may need to run sudo apt-get install screen before this works). Then go to VM2, open a terminal, and type echo "Hello" > /dev/ttyS0.
You should see Hello appear in the terminal open in VM1. When you're done running screen press ctrl-a k to kill it, otherwise if you try to do other stuff with the serial port you may get an error message saying that the port is busy.
When I had to do some serial port testing from my real to virtual machine I ended up doing a "loop back" type testing. I took two USB-Serial converters and a RS232 F-F adaptor and connected my machine to itself. Then in VirtualBox under Settings->USB you can route one of the two USB-Serial converters to be "owned" by your VirtualBox.
Once you plug in the converters one will register with the Mac and one with the Ubuntu "computer" then you can do serial communication as normal between the two machines.
You may also be able to emulate a virtual serial port using a pty ("pseudo-teletype" device), but I'm not positive on that one since I believe the ability to do that was locked down in newer kernels.
I ran into a similar situation running a QNX guest using VirtualBox 5.0.10 on an Ubuntu 14.04 host.
My solution seems general enough to apply to the above-mentioned case.
I configured the guest VM in the same way that Kells1986 setup his VM1:
Under the "Serial Ports"/"Port1" tab:
check "Enable Serial Port"
set "Port Number" to "COM1"
set "IRQ" to "4"
set "I/O Port" to "0x3F8"
set "Port Mode" to "Host Pipe"
uncheck "Connect to existing pipe/socket"
set "Path/Address" to an accessible file-system path (e.g. "/home/safayet/vmSerialPipe")
According to the VirtualBox manual:
You can tell VirtualBox to connect the virtual serial port to a
software pipe on the host. ... On a Mac, Linux or Solaris host, a local domain socket is used ... On Linux there are various tools which can connect to a local domain socket or create one in server mode. The most flexible tool is socat and is available as part of many distributions.
A domain socket is an IPC mechanism on UNIX systems similar to a pipe.
I connected to the "pipe" end of the virtual serial port on the Ubuntu host using the socat command:
socat - UNIX-CONNECT:/home/safayet/vmSerialPipe
Related
My Raspberry Pi 3 can connect briefly to my Android mobile, but once I accept the connection on the Raspberry Pi, I get this error:
GDBus.Error:org.bluez.Error.Failed: No such file or directory. Try to connect manually.
Please help me on this.
You can fix that from Bluetooth control. Type $bluetoothctl as root then you will end up with Bluetooth shall. There you should type "power on" command. After that you can use "scan on" command to check connection.
to continue from Dinusha's answer, after you scan and find your device's ID (you should also be able to see it's name in parentheses) you'll need to pair with the device by doing
pair <device ID>
then connect with the device by doing
connect <device ID>
You'll be able to see status of the connection
There are cases where I use a separate bluetooth dongle for connections I don't want dropped
Raspbian Jessie has some issues as far as I know with the Bluetooth module. I'd recommend using bullseye or buster. Also, there are a couple issues regarding the newest kernel. Run the following command to see if your phone which you are willing to connect is listed:
sudo bluetoothctl devices
If your mobile device is still listed here and not paired on the mobile side, there is your problem. Remove the device using the following command in RPI:
sudo bluetoothctl remove <mac-adress-of-device>
I have an embedded system that is programed in C. I need to do the equivalent to the DOS command Telnet. The idea is to test if the remote host is up and running.
I would like to have some orientation here like:
Open source project that I can use as a guide line (C language)
Some documentation on what the Telnet command does (so I can
implement my own)
Thanks
Update: Thank you for your valuable comments
My system connects to a host via GPRS/Ethernet/dial up/Wifi (one of them). As a developer I check if the host is ok by using my windows laptop (with a Dial up modem, GPRS modem or whatever is needed) and running Telnet like this:
telnet 192.168.0.1 8000
(non real values)
If the host is ok I got the clean screen, otherwise I got an error. That's what I need to do in code, to be able to determine if the host is up and running by using a sort of DOS telnet client command in C.
This is done once, just to check communications, after this test is cleared the real info should be sent.
I am trying to implement Bluetooth using "connect-blue-oem-spa-331" module using UART protocol and using MSP430 as base controller. I'm using Embedded C as a language of programming.
Everything just works fine until I reach to Serial Port Link Command "AT*ADCP". Every time I get response as ERROR. I have tried with both options by keeping ECHO ENABLED and ECHO DISABLED.
p_cmd = "AT*ADCP=XXXXXXXXXXXX,0,0,0\r";
this is my command. 'X' represents the Bluetooth confirm device address which I confirm when I execute DEVICE_INQUIRY command.
The module through which I am executing all these commands is always MASTER and will initiate pairing and communication process. As a safety I have kept it non-discoverable.
How can I implement the Serial Port Profile Link command without getting error when I confirm the bluetooth device using DEVICE_INQUIRY command.
I have been working with blue tooth for last 4 months. I had faced above issue in early days. And after running through documentation available for product I solved the issue. I thought to reply this question which I've asked.
I was using Connect Blue OEM-SPA-331i classic Bluetooth module in my project, and was using Serial Port Profile to implement Bluetooth commands.
When I inquire devices I get the list of Bluetooth Devices available and discoverable in the vicinity(mine was CLASS-I Device); and lists them as (48 bit MAC Address,Class of Device) i.e. ( 001234ab987f,786545) of the discovered Bluetooth Module.
When I'm trying to establish Serial Port Profile Link, it was required that I must write address of peer device to be connected over Serial Port Profile in Serial Port Adapter. The order of the commands should be
Inquire discoverable devices
Write the desired peer device address to Serial Port Adapter, remember it in power cycles.
Establish Profile Link.
This way I resolved my issue of link not getting established.
I'm developing a program that sends a file from one computer to another between a RS232 serial port.
I can test it on the school computers just fine, but I would like to be able to test it at home. So I'm trying to connect 2 virtual machines between a virtual serial port in vmware fusion, but I don't understand how to configure it.
I've installed the 2 virtual machines and added a serial port to each one (in the settings). But the only available option is to name the file that the serial port will use. This name will be used how?
I'm working with the /dev/ttyS1 port, can I still use it normally, and somehow redirect the output to the file that was configured?
So, it was easy. You have to use the same file in each virtual machine. When you try to save the same file on the second vm it warns you that the file already exists, just say you want to replace it. Go into the share settings of each virtual machine and add the folder where the file is stored on your computer, and give it read and write permissions. In my case is the same folder where I keep the vm files. Now I just have to open the file and exchange info between the 2 vm's. I had to comment a few things in my code (it's not a real serial port)but at least I can simulate it well enough.
I'm having trouble understanding the API to set up a l2cap (or RFCOMM) client/server running on OSX like I can with BlueZ on Linux.
On Linux, I simply open a socket, bind, listen & then accept for the server, & socket, bind, connect for the client (w/ the bind taking in the BT address of the device I want to use). Also, there's no pairing done.
I can't figure out how to configure my application to start listening for connections on a particular device (or if OSX only supports 1 BT adapater at a time, then how to listen for any incoming connections).
I also can't figure out how to configure my application to send to one BT device using a particular device (this is irrelevant if OSX only supports 1 at a time).
Also, does the OSX stack require pairing to have occured between 2 devices before it'll pass through l2cap?
Any language examples would be appreciated, although C/C++ would be preferred.
Thanks
In Mac OS X 10.5 there's an example (in /Developer/Examples/Bluetooth, titled RFCOMM_Open_SPP_Example) that shows connecting to and reading data from a bluetooth device (i've used it to read NMEA lines from a BT GPS receiver). See also: Leopard & Bluetooth RFCOMM channels
Unfortunately I can't find a copy of the example project anywhere.
It looks like the code samples have been replaced with: Developing Bluetooth Applications