Retro computing with a touch of modern and the home for all things, retroCombs (aka Steven Combs).

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7 August 2016

HOWTO: Make a Mac to C.H.I.P. USB OTG serial connection

by Steven B. Combs, Ph.D.

A key feature of the C.H.I.P. is the 4Gb onboard flash memory. Unlike a Raspberry Pi, the C.H.I.P. does not require a microSD card (making the cost to operate a C.H.I.P. even less than a Raspberry Pi). You simply connect the C.H.I.P. to your computer and “flash” the C.H.I.P. operating system. Once flashed, you don’t even need a monitor or keyboard to begin using thanks to Next Thing Co’s foresight to include a USB On-The-Go (OTG) connection.

USB OTG on a Windows box using Putty is documented online; however, I’ve yet to find specific details on how to make this connection on a Mac. After several failed attempts, I was able to make a USB OTG connection using my Mac. This post documents my process.

Flash the C.H.I.P.

Before a C.H.I.P. will work out of the box with a USB OTG connection, you need to install the latest operating system (OS). Choose the latest version (as of this writing 4.4). You will use the Chrome browser and the C.H.I.P. Flasher application to do this:

The use of a serial connection is baked in by the developers and is a very cool way to connect your C.H.I.P. to your home Wi-Fi and begin using your C.H.I.P. immediately. Let’s get to the fun stuff now.

Determine USB identification

This is a bit tricky, so follow closely. Load the Terminal application on the Mac and issue the command below.

ls /dev/tty*

You will see a long list of tty devices similar to the image below:

TTY Devices

Most likely, the C.H.I.P. tty device is not on the current page. Use the arrow keys and scroll up. Look for a tty device with the following format:

/dev/tty.usbmodemXXXX where XXXX is a four digit number

Write down that four digit number, or better yet, write that entire line with the four digit numbers. In my case, I have the following serial device name:

`/dev/tty.usbmodem2623 `

Connect using a Serial Terminal

The Mac has a serial connection command built-in called screen and we will use the screen command to make a serial connection to the C.H.I.P. so we can issue commands on the C.H.I.P.

If the connection is successful, the C.H.I.P. will promote you for a username and password. The defaults are below:

username: chip password: chip

After the login process, you will see the prompt in the image below:

A successful serial connection

You can now issue commands to the C.H.I.P. I will not discuss the many possibilities; however, I do want to share two useful things we can do with the C.H.I.P. and this serial connection:

  1. Connect the C.H.I.P. to Wi-Fi
  2. Determine the C.H.I.P. IP address

Once you do these two things, you can untether your C.H.I.P. from your Mac and administer it remotely.

Connect C.H.I.P. to Wi-Fi

To connect your C.H.I.P. to your Wi-Fi network, first see that your C.H.I.P. can access your network. Scan the Wi-Fi spectrum with the command below:

nmcli device wifi list

You will see a listing similar to the one below:

List of Wi-Fi networks

If you see the name of your Wi-Fi network (along with others depending on the proximity to your neighbors), you are ready to make a connection.

Use the command below:

sudo nmcli device wifi connect 'SSID' password 'password' ifname wlan0

Remember to make the substitutions to include your Wi-Fi SSID and password.

The C.H.I.P. will ask for a password. This is the C.H.I.P. user password, chip, not the Wi-Fi password. You will type blind and will not see the password or * placeholders.

Enter chip and hit the enter key. After a second or two, you will see a line similar to the following:

Connection with UUID '211yui4-d0fc-601c-4ddeb-3b4f5z690d0b' created and activated on device 'wlan0'

Success! The C.H.I.P. will remember the Wi-Fi connection even after a reboot.

Now determine the C.H.I.P. IP address so you can untether the C.H.I.P. from the Mac and make a remote connection via SSH.

TIP After I wrote this post, I discovered a visual way to configure the Wi-Fi network. Issue the nmtui command and you will see a terminal “blue-box” that will guide you through this process using a terminal dialog box. Pretty slick.

Determine IP Address

To determine the C.H.I.P. IP address, use the command below:

ip add show

The C.H.I.P. will display IP information. Look for your local network IP range and write it down. At this point, I recommend you also write down the MAC address of the device.

The IP address will likely change if you reboot your device often. I recommend you configure your Wi-Fi router so it receives the same IP address each time the C.H.I.P. connects to the network.

You can also assign a hostname that assigns a name to the device such as:


You should be able to find instructions for both of these tips with a quick Google search.

Use the C.H.I.P. untethered

You can now use the C.H.I.P. untethered. To close the serial connection, type:


Leave the C.H.I.P. plugged into the Mac and connect via SSH. You can also plug the C.H.I.P. into a power source anywhere in your home and connect via SSH and allow your C.H.I.P. to become a server.

If you flash the C.H.I.P. with a GUI, you can control the C.H.I.P. using that GUI if you follow my x11vnc instructions.


Let me know if there is an error in my write-up using the comments below. It’s a lengthy post and I may have fat-fingered a step. I hope Mac users with a new C.H.I.P. find this useful. It took me some time and troubleshooting to figure this out, but I learned a lot along the way.

What will you do with your untethered C.H.I.P.? I would love to read your ideas. Drop those in the comments as well.