BackgroundThe main reason why you need any program like minicom to communicate over a serial port is that the port needs to be set up prior to initiating a connection. If it weren't set up appropriately, the cat and echo commands would not do for you what you might have expected.
Notice that once you run a program like minicom, the port is left with the settings that minicom used. You can query the communication settings using the stty program like this: stty.
Picocom also will let you connect to a serial port without reconfiguring it ( -noinit) and will let you exit without restoring the serial port configuration ( -noreset or use Ctrl-A/ Ctrl-Q to quit picocom). I've found picocom to be much easier to use than minicom.
For reasons I haven't figured out, minicom will sometime simply not send or receive data on a port that worked moments before or that picocom has no trouble with. It's probably some arcane configuration option, but whatever it is I can't figure it out (and this behavior has happened on more than one machine).–Oct 24 '13 at 21:11. I found a way using a shell script that put cat as a background process and a while loop that read the user input and echo it out to the port. I modified it to be more general and it fitted my purpose perfectly. #!/bin/sh# connect.sh# Usage:# $ connect.sh # Example: connect.sh /dev/ttyS0 9600# Set up devicestty -F $1 $2# Let cat read the device $1 in the backgroundcat $1 &# Capture PID of background process so it is possible to terminate it when donebgPid=$!# Read commands from user, send them to device $1while read cmddoecho '$cmd'done $1# Terminate background read processkill $bgPid. Howerver, the real gotcha in your script is that the background process is only killed if you press Ctrl+D to end your script, because that ends the while loop cleanly.
If you kill it with Ctrl+C or with the kill command, then the cat process stays alive. To fix that you would need to use the trap command to execute kill $bgPid when the shell exits, like. Honestly, I wouldn't even mind if you just added my whole script to your post.
Hexcmp2 2 34 Serial Port Switch
I tried to do that, but the edit was rejected.–Sep 26 '16 at 11:08. This script is based on, but sends everything over the serial port (except Ctrl+Q), not just single commands followed by Enter. This enables you to use Ctrl+C or Ctrl+Z on the remote host, and to use interactive 'GUI' programs like aptitude or alsamixer. It can be quit by pressing Ctrl+Q. #!/bin/bashif $# -lt 1 ; thenecho 'Usage:'echo ' femtocom. Putty works well on Linux and offers some convenience, especially for serial communications.
It has one drawback I haven't been able to directly solve: no copy-paste from the Putty window itself. The windows version has a lovely auto-copy to clipboard on highlight, right-click to paste behaviour (and there are excellent plugins for both chrome and firefox to enable the same behavior), but on Linux, no copy love AFAIK.If the lack of copy is a problem (it is for me) then turn on logging in putty and open a standard terminal window and # tail -f putty.log and bidirectional text is available for standard copypasta action. I find that Putty under Linux doesn't paste 'the clipboard' (what you copy with control-C), but it will insert 'the primary selection' (what you have currently selected in some program) with middle-mouse. Likewise you can select characters in Putty's screen to define the primary selection. But if I want text from a Putty screen to transfer to some VM, I need it to be the clipboard, so I have to use an intermediary program to receive the text from the main selection and then copy it to the clipboard.–Feb 28 '17 at 19:58. It depends on what you want to do.
Do you want to run a shell or applicaiton interactively from the terminal, connect out to another computer over the serial line, automate communication with a device over a serial port?If you want bidirectional communication then I presume you want something interactive with a human on the terminal. You can configure the system to allow logins from a terminal over a serial port by seting up a session on the serial port - getty is the tool for setting up a terminal and allowing logins onto it. Put an entry in your file to run it on the appropriate serial port on a respawn basis.If you want to connect to a device and initiate automated two way conversations then you could see if will get you what you want. Use to configure the port to the right parity, baud rate and other relevant settings.If you want to communicate interactively with another computer over the serial port then you will need terminal emulation software. This does quite a lot - it sets up the port, interprets ANSI or other terminal command sequences (ANSI was far from being the only standard supported by serial terminals).
Many terminal emulators also support file transfer protocols such as kermit or zmodem.The ins and outs of serial communications and terminal I/O are fairly complex; you can read more than you ever wanted to know on the subject in the.
I recently bought an (old) laptop from someone, and despite having installed virtually no programs on it the Device Manager lists a Communications Port assigned to COM1. Attempting to use COM1 for another purpose brings up a dialogue saying that it's in use and needs to be disabled first, though even when I disable it, I have no luck getting the cable I'm working with to work on that port. What does the Communications Port on COM1 do - what is it used for?
And as a bonus, how do I clear it up so that I can use COM1 for what I need to use it for?Thanks. The cable you are trying to use is a serial-to-USB converter. You would have to install a driver for such a device. The driver would then emulate a COM port, but these devices are notoriously hard to get working right because USB ports are inherently plug-and-play, but serial ports are not (they existed long before Windows).If your computer actually has a real serial port on it, then that's the COM1 you're seeing, and of course the software wouldn't be able to use it because it isn't connected to that port. The driver for the device should be emulating a COM2 or something similar.If your computer does not have a real serial port on it, then COM1 probably is that device you're trying to use.Either way you slice it, however, this is a problem with the software for the device not being configured correctly.
Ensure that the COM port isn't disabled in the BIOS of your PC. You may also need to configure the COM with terminal emulation software with appropriate settings which the connected devices both use for the communication e.g.
Speed, parity, data, and so on.The Microsoft MS-DOS and Windows environments refer to serial ports asports: COM1, COM2.etc. Ports numbered greater than COM9 shouldbe referred to using the.COM10 syntax.Additionally, you may want to look over for another basic starting point.I/O addressesThe COM ports are interfaced by an integrated circuit such as 16550UART. This IC has seven internal 8-bit registers which holdinformation and configuration data about which data is to be sent orwas received, the baud rate, interrupt configuration and more. In thecase of COM1, these registers can be accessed by writing to or readingfrom the I/O addresses 0x3F8 to 0x3FF.If the CPU, for example, wants to send information out on COM1, itwrites to I/O port 0x3F8, as this I/O port is 'connected' to the UARTIC register which holds the information that is to be sent out.The COM ports in PC-compatible are typically defined as:. COM1: I/O port 0x3F8, IRQ 4. COM2: I/O port 0x2F8, IRQ 3. COM3: I/O port 0x3E8, IRQ 4.
COM4: I/O port 0x2E8, IRQ 3. I understand what COM ports are, but I was more looking for an answer as to what this particular default Communications Port does - what it's assigned to, and what disabling it might effect. It was there by default on a fresh installation of Windows 7, and I'm trying to figure out: a) what's using it, and b) how I can safely disable it so COM1 can be used for my purpose. Would it just be as simple as reassigning that port using the Device Manager to COM2, for example, and then assigning the cable that I'm using to COM1?–Jul 14 '16 at 22:25.
Hexcmp2 2 34 Serial Port Charlotte
What's using COM1:As listed in the screen shot on your answer of the Device Manager, it appears that COM1 is assigned to the Communications Port.