Mac os x usb serial console

When you plug your board in to USB on your computer, it connects to a serial port. The port is like a door through which your board can communicate with your computer using USB. We're going to use Terminal to determine what port the board is using.

Mac's and serial TTY's

The easiest way to determine which port the board is using is to first check without the board plugged in. On Mac, open Terminal and type the following:. It has a name that starts with tty. The command ls shows you a list of items in a directory. This will show us the current serial connections. For Linux, the procedure is the same, however, the name is slightly different. If you're using Linux, you'll type:.

The concept is the same with Linux. This will show you the current serial connections. In the example below, the error is indicating that are no current serial connections starting with ttyACM. Yours will be called something similar.

Getting a getty running

The ttyACM0 part of this listing is the name the example board is using. Now that you know the name your board is using, you're ready connect to the serial console. We're going to use a command called screen. The screen command is included with MacOS. Linux users may need to install it using their package manager.

To connect to the serial console, use Terminal. The first part of this establishes using the screen command. The second part tells screen the name of the board you're trying to use.

The third part tells screen what baud rate to use for the serial connection. The baud rate is the speed in bits per second that data is sent over the serial connection. In this case, the speed required by the board is bits per second. Press enter to run the command. It will open in the same window.

Installing a USB Serial Adapter on Mac OS X - Plugable

If no code is running, the window will be blank. Otherwise, you'll see the output of your code. If you try to run screen and it doesn't work, then you may be running into an issue with permissions. Linux keeps track of users and groups and what they are allowed to do and not do, like access the hardware associated with the serial connection for running screen. So if you see something like this:. There are generally two ways you can do this.

The first is to just run screen using the sudo command, which temporarily gives you elevated privileges. The second way is to add yourself to the group associated with the hardware. For an example of how to alter the device ID or disable the built-in driver follow just step 1 , see this blog post. In the process of doing this myself, I learned a bit about the kernel extension of which these drivers are each an instance system in OS X. The basic idea is that each has a [drivername]. For an immediate load or unload, run kextload [path to.

To see the list of currently installed extensions, run kextstat e. After re-enabling a driver, the driver may not reload even after the next reboot because a separate cache of kernel extensions is kept to speed up enumeration on boot. The next step is to test the serial port using some sort of terminal emulation program. I used goSerial , which happened to be the first one I found.

Using MAC terminal with Prolific USB serial PL2303

It worked fine for my purposes, but better ones may exist. In the Unix world, getty is the program that presents a login prompt. It appears that as of Instead, I found that creating a script to spawn the getty that is run by launchd does the trick. I therefore created a file called serialconsole.

Note that first bit sets the daemon name, the second bit sets the program arguments one "string" per argument , and the last bit keepalive instructs launchd to restart the daemon when it exits eg, the user logs out of the console. As noted later, the "cu. Initially, this was reported in only some cases but seems to be the norm as of Using the program launchctl, you can manually reload these configuration files and restart daemons. Here are some self-explanatory commands you might use, of which only the first two should be necessary to start the getty manually after creating the configuration file above.

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Of course, rebooting should also work if you're lazy. However, the next time it attempts to restart it within a minute or so , it should succeed. Check that log file for other errors. As of Supposedly the following is the preferred sequence:. However, in my case these did not seem to be sufficient, whereas launchctl load did the trick.


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Let me know what seems to work for you. For my application, I wanted a shell prompt to be immediately presented, without asking for username or password or displaying the login messages last time logged in, new mail, etc. The reason this additional script was required was due to stupidity on the part of the login program that I observed.

First, it seems to ignore the presence of a. Further, the -f argument passed to login must be first on the command line before a "-q" which forces quite mode. See the login man page for some of idea of what I'm talking about. The above script performs this necessary munging.