Mac Terminal Serial Emulator Screen Resource Busy

A basic tool for testing your serial port connection on your Mac isCoolTerm by Roger Meier:


Trying to communicate to device attached to serial port on Xserve through terminal.terminal froze after first try (hardware related), however, now - after fixing hardware - when we try to connect using: screen /dev/cu.serial 115200 we get two errors in rapid succession: Cannot open line '/dev/cu.serial' for R/W: Resource Busy. Serial Port Access on your Mac with CoolTerm¶ A basic tool for testing your serial port connection on your Mac is CoolTerm by Roger Meier: CoolTerm is a simple serial port terminal application (no terminal emulation) that is geared towards hobbyists and professionals with a need to exchange data with hardware connected to serial ports such as. This is the normal terminal emulation mode that most people use, anyway. On the Linux side, the serial line must be configured with a getty on it to start a login: shell. To do this, you need to tell init that the serial line has a terminal on it.

CoolTerm is a simple serial port terminal application (no terminalemulation) that is geared towards hobbyists and professionals with aneed to exchange data with hardware connected to serial ports suchas servo controllers, robotic kits, GPS receivers, microcontrollers,etc.

You can download CoolTerm here (mirror).

Step 1 - Start CoolTerm¶

CoolTerm is idle state when you open it. First you need to select andconfigure the serial port by pressing the options button.

Step 2 - Configure and select the Serial Port¶

Configure the serial port and select the serial port. If CoolTermdoesn’t show your serial port, you need to press the Re-Scan SerialPorts button. The serial port should show up in the selection list, ifit doesn’t show, please check if the driver has been installed correctly (see support).

Press the ok button when you’re finished.

Step 3 - Use the Serial Port¶

CoolTerm is still Idle, press the Connect button to open the serialport. After pressing this button the character your type are send to theouter-space via the serial port, and characters it receives aredisplayed in the window. You can also monitor the handshake signals viathe signal LEDS in the right corner, and you can control the RTS and DTRsignal by pressing the signal LEDS

Use 'screen' as a serial terminal emulator 29 comments Create New Account
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Can you not just save all that as terminal profile and then double click it, or select it from the Terminal dock menu? No applescript involved.
~/.sig: not found

I use the following keyspan.term (string-style plist for readability): Note that you can control the terminal baud rate and other characteristics with the last argument (see the WINDOW TYPES section of screen(1)).
Or just use QuickTerm

I am not a programmer. What shall I do when I've setted the port of QuickTerm, and came back to the window 'RS-232 Terminal'.
I clicked on 'Connect'. It probably connected but the window is empty, I cannot type anything in it, and anyway I don't know what to type.
I want to use it for our French 'minitel'. I think it is V33, but not sure.
I use a laptop and MacOs 10.4.9.
My modem is inside :
Modele : MicroDash
Type d'interface : USB
Modulation : V.92
Nom de serie : Euro
Version Matériel : 1.0F
Version du programme interne : APPLE VERSION 2.6.6
Gestionnaire : InternalUSBModem.kext (v2.6.6)
Pays : 3D (France)
Is X11 necessary ? I am not keen on the terminal, so could you give basic explanations.
Thank you.

Mac Terminal Serial Emulator Screen Resource Busy Software

No need to shell out for Keyspan's admittedly very good drivers. Many USB-serial adapters use the same chip, Prolific Industries' PL-2303 controller. Prolific's own Mac OS X driver is currently not very good; you can't send a break signal via screen in Terminal, for example. However, there's an open-source driver that works better.

I use this with an unbranded PL-2303-equipped adapter bought from eBay for six of our English pounds, compared to thirty-odd for a Keyspan device, and it talks perfectly to my Cisco routers. I haven't tried talking to PDAs or GPS devices though.

'Shell' out. See what I did there? Heh - oh dear.

You can also use C-Kermit 8.0. Unfortunately a binary is not available, we must compile it by ourselves, but it's really easy, as Mac OS X is supported.
Download the source at the following address:
Copy it in a folder, then, using terminal:
% cd <the folder you copied it in>
% unzip -a
% make macosx103
% sudo make install
it will compile and install Kermit in the folder /usr/local/bin/kermit; the binary is called wermit.
It's ready! to launch it:
% /usr/local/bin/kermit/wermit
and here it is:
C-Kermit 8.0.211, 10 Apr 2004, for Mac OS X 10.3
Copyright (C) 1985, 2004,
Trustees of Columbia University in the City of New York.
Type ? or HELP for help.
(/Users/wallybear/) C-Kermit>
Compiling from source give also the chance to tweak compiler settings so to make a PPC, Intel or Universal binary application.
I last used C-Kermit when Jaguar was out. It worked great. PowerPC binaries for 10.3 and earlier can be found here:

Wow! Kermit - I haven't used that for at least a decade, but I seem to remember that it was very good.. must give it a try..

Anyway, that aside, for those who like minicom, Jeffrey Frey has done a Mac port which can be found at the bottome of his page here:

also the awesome thing about kermit which i've been using recently for a few years is that it lets you send files via xmodem (useful when ur cisco gear pukes on itself), and also kermit is scriptable (useful when you have 50+ apc power strips you have to configure the same way, enter non-interactive script).

I'm not saying I'd recommend it, but you could also use tip, 'man tip' for more info.

osx unfortunately doesn't come with tip . i was disappointed quite a bit when I found out

There are quite a few installer packages for minicom that remove the need for fink or darwin(er. mac)ports.
one's at

This is an excellent solution (I've been a regular, frustrated, user of ZTERM). I am, however, unable to configure the serial port settings (I routinely connect to a serial device running 38400/n/8/1) I've tried every combination I can imagine with stty to set the port before starting screen and it is still always stuck at 9600 baud.

Update: I found on Apple's discussions board the following, which works:
screen -U /dev/tty.KeySerial1 38400
Adjust the script accordingly and it works perfectly!

Here is an addition I made to select the serial port and the baud rate:

set baudList to {1200, 2400, 4800, 4800, 9600, 19200, 38400, 57600, 115200, 230400}

Dot net 3.5 offline installer. set baudRate to (choose from list baudList default items {38400})

Mac Terminal Serial Emulator Screen Resource Busy Number

tell application 'Terminal'

set serialDevices to (do shell script 'ls /dev/cu*')

set theDeviceList to (paragraphs of serialDevices) as list

set theDevice to (choose from list theDeviceList)

do script 'screen ' & theDevice & ' ' & baudRate

display dialog 'To quit you terminal session type then '

end tell

Mac Terminal Serial Emulator Screen Resource Busy Mode

the second to last line should have been:
display dialog 'To quit you terminal session type <ctrl-a> then <ctrl->'

Serial Port Terminal Emulator

The second to last should have read:

thanks for all your help, especially bboy for the cheaper cable, and wcontello for the AppleScript.
I am currently taking 2 classes that use HyperTerminal, a Cisco test prep class and a basic Telecommunications classes. I've wanted to use my MacBook Pro to use something HyperTerminal related. I have a beta of Windows 7 in Boot Camp and VMWare, and MS got rid of HyperTerminal in Vista. And of course no Mac (except for Xserves) have a serial port.
Startup Shortcuts - Shortcuts for debugging your Mac on startup, on your iPhone

You wrote: 'type Control-A followed by Control- to exit your screen session. If you fail to do this and exit a Terminal session, you'll leave the screen session alive and the serial resource unavailable until you kill the screen session manually.'
OK, I boo-booed. Now how can I kill the screen session manually?
(I wish I knew Unix better.)

Look for a process called 'SCREEN' using ps. Here's the output of my Terminal:

Kill the process associated with SCREEN (i.e. 'kill -TERM 327'), and the SCREEN will go away.

You can also reattach to a detached screen by running 'screen -rD'.

Another solution would be using the ZOC Terminal application. I used zterm initially and found it horrible too. ZOC is a lot more modern in every regard and works with a serial/usb adapter.

If you want to use screen as an terminal, but don't want it to go into the background when the window dies, you will need to turn off auto-detach.
To do this, edit ~/.screenrc (it probably won't exist) and add the following line:
autodetach off
The next time you start screen, if you kill the window you will kill the session.

How about simply 'cu -l /dev/whatever -s 19200' and that's all it takes.

Thanks! Working great w/an IOGEAR GU232A USB to Serial adapter which uses the PL2303 chip set.

This is a fantastic thread. Saved me from using Zterm. One problem though. I'd like to be able to scroll up past the top to show more than one page of data. Anyone figure out a way to do that?

Never mind. A little googling found the answer I was looking for. To turn on the scrollback buffer for SCREEN you have to add one more line to ~/.screenrc More info here:

since people are still posting to this 4 year old thread, I think it's useful to point out that iTerm - - is a cocoa terminal editor that is up to date and under continued development (and that's not to mention the Terminal application packaged with os X).

I found Furrysoft's goSerial rather nice for my AVR hacking projects: