1. Jeremy Sandoval University of Washington May 14, 2013
Using UART Protocol to Communicate between the Digilent Atlys Board and PC
Jeremy Sandoval
University of Washington
May 14, 2013

2. Overview Defining UART protocol UART purpose
Getting started using UART
How to test a UART Project
Configuring the COM port
Results
Next Task

3. What is UART? Universal Asynchronous Receive/Transmit
Universal means data format and transmission speeds are configurable
Asynchronous means no clock line
UART takes bytes of data from one end and transmits them in individual bits in sequential order.
When data gets to destination, the bits are reassembled back into bytes.
Advantage of UART:
Less costly to utilize two wires to send information in serial format than multiple wires to send information in parallel format

4. UART Continued
Method to communicate between the Spartan-6 Atlys Board and PC via a COM (serial) port
The Atlys board contains an EXAR USB-UART Bridge
The EXAR part XR21V1410 can deliver the data to the Spartan-6 using a two-wire serial port to pins A16 and B16
Source:

5. Purpose What purpose could UART fulfil in the IBLROD project?
Debugging
When the General Purpose Input/Outputs (GPIOs), mainly the on-board LEDs, cannot be used to display an internal information
Or need more detailed information to understand what a specific process is doing

6. Getting Started with UART
Began by downloading a demo project from Digilent’s website
Contained the ISE project that demonstrated the use of the General I/O and UART
Operation shown in state diagram:

7. State Machine Explained

8. Testing the UART Demo Project
In order to test the project need to:
Upload .bit programming file to Atlys board
Download EXAR USB-UART driver and install on the PC
Install Tera Term, a terminal emulator program that will used as a serial communication port on the PC
Switch USB cable from PROG port to UART port on Atlys board

9. Setting up the Serial Port
In order for Tera Term program to properly read and display information, the connection settings must be set as specified in UART Demo top level module comments 
Baud rate: data transmission speed bits/sec
Data: 8 bit characters sent
Parity:  Bit that acts as a check on a set of binary values (not used)
Stop: One of a pattern of bits that indicate the end of a character

10. Results
Pressing the left, right, up, or down button will display button pressed message
Pressing center button will display welcome message
LEDs connected with on-board switches at all times except when center button is being pressed For this operation, LEDs are tied to ground (won’t turn on with switch)

11. Next Task… Understanding ChipScope and Plan Ahead
Xilinx tools that make it easier to debug and verify FPGA designs