Sending Data through UART USB dongle on Mac OS X

The Universal Asynchronous Receiver/Transmitter (UART) is a hardware that enables data transmission between parallel and serial form. Common UART communication protocols include RS-232, RS-422 or RS-485.  I believe engineers who have lived in PC-era have used this cable before:

Today's computer no longer has RS-232 port. Fortunately, UART still exist in our life, just in different form:

This is USB-UART dongle made by FTDI chip. The chip on the board emulates a UART port so we can still use old technology to communicate with new chip, such as TI's Bluetooth Low Energy (BLE) chip CC2540.

So how can we connect to USB-UART? Actually Mac OS X has a command  "Screen". Just open an terminal and follow the steps below:

1. list the USB-UART device:

  $ ls /dev/cu.*                                                              
    /dev/cu.Bluetooth-Modem         /dev/cu.usbserial  

    This command will list the connected devices on your Mac. Our target is usbserial

2. Connect to the device, simple type the "screen" and baud rate:

  $ screen /dev/cu.usbserial 115200  

    The number 115200 is the baud rate used to communicate between two devices

3. To leave the screen, type CTRL-A then CTRL-\ 

Also there are many GUI tool can be used. I recommend using CoolTerm:

http://freeware.the-meiers.org/ 

A good Coolterm tutorial can be found here:

https://learn.sparkfun.com/tutorials/terminal-basics/coolterm-windows-mac-linux

CoolTerm is written in VB and can also be run on multiple platforms (Windows & Linux), which is a very convenient feature.