Its a good idea to test your Bluefruit EZ-Link, that way you can tell if there's something wrong with your microcontroller or wiring - you can at least rule out the EZ-Link from being the problem.

To test, you'll need a terminal program. Since most people have the Arduino IDE installed, I'll use that for the first 'loopback' test

Loop-back Test

The loopback test is the easiest test and checks the RX/TX pins as well as the wireless link overall!
Start up the Arduino IDE and select the Bluetooth device you found in the Pairing step beforehand
Then open up the Serial monitor. It may take a few seconds to make the link. You should see the red LED on the EZ-Link blink very fast now to indicate a connection is made

Type some text into the entry box and hit return, you should see nothing appear in the monitor
Now connect a wire from the RX to the TX pin on the EZ-Link
Now go back to the Serial Monitor and type in a new message & hit return
This time, you'll see whatever you send is echoed back to you - that way you have tested that data can be sent wirelessly to the EZ-Link, through the wire, and then back to your computer. If you watch closely you can also see the blue LEDs flicker


This is a more advanced test, for checking the DSR/DTR pins. For this, we need a terminal program that can control the flow lines. Unfortunately the Arduino IDE does not do this, but Digi's X-CTU program can.

If you're on a Mac, Serial Tools will let you perform the same tests as X-CTU is not available for Mac

Select the COM port you identified before
And click on Terminal to open up the serial monitor/entry window
X-CTU has the nice ability to show you data sent and received at once, which makes it easy to do the RX-TX loopback test as above, you'll see each character echoed
To do the DTR/DSR test, connect a wire from DSR to DTR line below
Then click on the DTR checkbox, this will toggle the DTR line on the EZ-Link, which will then feed back to the DSR line which will toggle the green DSR labeled box to the left. Make sure you see the green box turn on and off when you click the checkbox!
This guide was first published on Nov 18, 2013. It was last updated on Nov 18, 2013. This page (Testing) was last updated on Jul 15, 2019.