Getting Started With Minicom
Contents
Background
minicom is a serial communication program that connects to devices through a GNU/Linux PC's serial ports. If run by calling its name without any additional arguments, it uses whatever settings have been saved for its defaults in /etc/minicom/minirc.dfl. For those using Windows, PuTTY is a viable application to make such connections between a Windows PC and one of our EMAC devices. More information about PuTTY can be found at http://wiki.emacinc.com/wiki/PuTTY.
Please note that while PuTTY will work, it is missing a number of features relative to a real Linux terminal. In particular, a number of keystroke shortcuts will not work with PuTTY, and not all output will be displayed correctly in PuTTY (although it does manage to display most output correctly). For serious work with Linux, a real Linux terminal (such as minicom, described here) is strongly recommended.
General Information
The use of a terminal emulator, such as minicom, is required when connecting to an EMAC board via a serial console. This page sets out to provide general information about using minicom to communicate between EMAC machines and a development PC.
Getting Started With Minicom
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If
minicomhas yet to be installed on your Linux machine, useapt-getto install theminicompackageuser@developerpc:~#sudo apt-get install minicom -
The
minicomsettings will need to be changed so that the application will be able to find your device. Pull up the settings using the-soption.user@developerpc:~#minicom -sThis should bring up a colorful display listing the different settings. If the display isn't colored, arrow down to Exit from Minicom. Run the
minicomcommand with the option-con. Thecspecifies the color display andontellsminicomto display the interface in color.minicomcan be made to always run in color by modifying the~/.bashrcfile, setting an alias forminicomtominicom -con, and restarting your terminal session (or sourcing your.bashrc) to make the change take effect.:alias minicom='minicom -con'
WARNING! You shouldn't need to run minicom with sudo. If you do, you have your permissions misconfigured. You'll need to add your user to the dialout group. I tried using adduser from my machine and it said I'm already in the
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The first thing that will need to be configured is the Serial port setup. Arrow down to the title and press the 'Enter' key.
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To modify the different configurations, press the key corresponding to the setting. For example, press the 'A' key to modify the path to the Serial Device. Press the 'Enter' key to save the parameters for the setting. The settings for specific EMAC devices can be found at the Serial Connections page.
In this screenshot, the "115200 8N1" for the Bps/Par/Bits setting indicates the baud rate is set to 115200, data bits set to 8 (the '8' in 8N1), parity is set to none (the 'N' in 8N1), and stop bits is set to 1 (the '1' in 8N1). You will most likely wish to modify the Serial Device setting to have the path to the serial port you normally use. This way, you'll be able to run the command without any options or commands. Press the 'Esc' key to be be brought back to the configurations page.
WARNING! You need to tell them how to find and configure their serial port as well. I wrote a program called scanserial, which is part of the emac-tools-util package, for just this purpose. It doesn't seem to have been documented on the wiki yet, though. You can provide a link to a stub article, which will be written soon. I'll create it here: http://wikidev.emacinc.com/wiki/Scanserial
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The next setting that needs to be configured is the Modem and dialing. Press the 'A' key and delete its content. Hit the 'Enter' key to set the setting as blank. Also do this for B through K, and for H. Hit the 'Esc' key when finished deleting the content of these settings.
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That's all the modifications that need to be done to get
minicomset up. Arrow down to Save setup as dfl and press 'Enter'. If a message pops up saying "cannot write to /etc/minicom/minirc.dfl",you likely aren't running the command as root. Re-run the command withsudo.
WARNING! Again, you shouldn't need to run as root. If you need sudo, your permissions are incorrect. They need to be fixed. The reason for getting this error would be because of running minicom with sudo to set the config the first time, because doing so would cause minicom to write a config file in your home directory that's owned by root instead of by you.
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Once you have saved the configuration, arrow down to Exit from Minicom.
Running Minicom
Now that everything is configured, you are ready to open the serial connection.
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Run the
minicomcommand to startminicomwith the serial port setting you configured above. If you wish to useminicomon a different serial port than the one you configured above, see the note below. -
Log in with the appropriate username and password for the device. Login information can be found here. You're now able to communicate to the device and use
minicomin the same way as using the terminal for the device.
| NOTE |
| The description of how to run minicom -D should be here. Remember, the customers reading this will usually only have one EMAC board, which they will keep attached to their computer for several months straight (if not 1+ years). |
Conclusion
This program is a very important tool for developers. The serial console is essential for working with the bootloader on ARM systems, since U-Boot cannot be accessed via ssh. Using the serial console, you will be able to configure the bootloader, to program new kernels via the bootloader, to program new filesystems, to make a copy of the filesystem on a board, and to perform memory checks using U-Boot. The serial console will also enable you to see startup and shutdown messages, to configure and debug the system when networking is not configured or is not working, and to debug the system when the machine is not booting up.
Further Information
Where to Go Next
