First, let’s figure out the path to our serial device. Ubuntu typically places these devices at /dev/ttyUSB#. Use the following command to determine the appropriate number of your device.

$ ls /dev/ttyUSB*

Now we’ll install Minicom to get started.

$ sudo apt-get install minicom

Once that’s complete, we’ll need to configure Minicom so that it’s using the correct port. To do this, run the command below.

$ minicom -s

You’ll be prompted with a configuration menu. Arrow down to “Serial port setup” and press enter.

+--------------------------------------------------------+
| A -    Serial Device      : /dev/ttyUSB0               |
| B - Lockfile Location     : /var/lock                  |
| C -   Callin Program      :                            |
| D -  Callout Program      :                            |
| E -    Bps/Par/Bits       : 115200 8N1                 |
| F - Hardware Flow Control : Yes                        |
| G - Software Flow Control : No                         |
|                                                        |
|    Change which setting?                               |
+--------------------------------------------------------+

The first line will give you the path to the serial port Minicom is going to talk to. If this doesn’t match the /dev/ttyUSB# path you found above, hit “A” on your keyboard and enter in the correct path and press enter. Now double check your Bps/Par/Bits settings. The default 9600 8N1 is pretty standard, but you may need to hit “E” and provide a different Speed setting depending on the device you’re talking to. In my case, OpenLog is running at 115200bps, so I went through and made the appropriate changes. Hit enter again to exit the serial port settings menu. The other settings can usually be left to their default values, so arrow down to “Save setup as dfl” to save this configuration as default. This way you don’t have to configure Minicom every time you use it. Now arrow down to “Exit” and hit enter. Minicom will now start up using the settings you specified. If all goes well, you should now be connected to your device and ready to send/receive. From now on, you can start minicom without the -s switch.

$ minicom

Got a better HyperTerminal replacement that you use in Linux? Let me know about it in the comments.

I expect that you have the Arduino IDE installed and running properly. This means the avrdude and avr-gcc libraries necessary to flash OpenLog will already be installed. Next step is to pull the firmware source code from the GitHub repository. If you don’t have git installed, run the following command:

$ sudo apt-get install git-core

Now you can run the git command to pull the source code over the read-only HTTP path. This is generally the easiest path to use to avoid issues with proxies or closed/blocked ports on your network.

$ git clone http://github.com/nseidle/OpenLog.git

Once the command has completed, you’ll have an OpenLog directory in your currently active directory. Time to compile the source code to make the required hex file that we’ll write to OpenLog.

$ cd OpenLog/Code/

$ make

You should see several notices about compiling various .c files, linking main.elf, and most importantly loading main.hex. Now we need to get that hex file onto OpenLog. Grab your trusty FTDI breakout board (you should never leave home without it) and wire it to OpenLog as shown below.

Before connecting the FTDI to your computer, we want to make sure we have the correct device path for the next step. Look at the list of all tty-capable USB devices. It’s okay if none show up right now.

$ ls /dev/ttyUSB*

Now connect the FTDI board and run the command again. The new ttyUSB# device listed is your FTDI board. I’ll use ttyUSB0 in the command below, so you will need to change the zero if your # is different.

I hope you have an extra wire at hand. The Linux build of avrdude unfortunately doesn’t have the “DTR wiggle” necessary to automatically reset OpenLog’s ATMega328p, so we have to do it ourselves. Grab a wire and connect one end to ground. If necessary, the microSD socket’s case can be used as a ground if you don’t have OpenLog on a breadboard. You’ll need to tap the other end of the wire onto the GPIO pin 6 on OpenLog. This is the square pin pad near the “O” in “OpenLog” on the silkscreen (the bottom-left most pin in the image featured above). Timing here is of the essence; run the command below, hit enter on your keyboard, then immediately tap the other end of your grounded wire to pin 6. Don’t leave the wire sitting on pin 6, it’s just a quick tap to momentarily ground it and force a reset.

$ avrdude -p atmega328p -P /dev/ttyUSB0 -c stk500v1 -b 57600 -U flash:w:main.hex

Don’t forget to change the ttyUSB# number if necessary. If your timing was good enough, you should see avrdude show a progress bar as it flashes the hex firmware onto OpenLog. If not, you’ll likely see errors like “programmer not responding” or “out of sync”. Try try again. Tapping enter and grounding pin 6 should be almost instantaneous, with the enter key coming ever so slightly first.

After a few seconds, the updated firmware will now be on your OpenLog chip and you’ll be on your merry way. I hope this helps someone out there.