An implementation of a basic character LCD controller in Verilog

For a while now, I have been wanting to post my code that I developed during my GPS project using a FPGA board. Creating the LCD controller module was the meat of the project and I know many people are interested in how one might approach such a project. I have plans on providing a full-fledged tutorial on how I designed this module, but it is still in the works. In the meantime, I will provide you with the Verilog code which is fairly well commented and with a little cross correlation with the data sheet for the ST7066 the code should be for the most part, self-explanatory. Eventually this post will be edited with a more formal discussion of this code but for now we will have to make due with just the code.

Here is a screenshot of a simulation of what this module does after the initialization phase and you write the ascii value of "C" (0x43) as a data operation. The markers indicate the start and end of the module's execution of this operation.

DOWNLOAD: FPGA_2_LCD.v

GPS to 16x2 Character LCD Using an FPGA

This is a project that uses a Spartan-3E FPGA Board (Xylo-LM) to grab the serial stream transmitted by a Locosys LS20031 GPS Module and parse the messages for the latitude and longitude. The latitude and longitude values are then feed into a 16x2 Character LCD display on a push of a button.

Note: The GPS coordinates shown will not lead you to me. The GPS module at the time of recording this, was not locked onto my coordinates...so don't try hunting me down..else you will find yourself in the Atlantic =P

Below is a basic block diagram that helps to illustrate what the FPGA does in the system. The FPGA has 3 modules: A Serial Module, a Parser Module, and an LCD Controller Module. The serial module is only responsible for acquiring the serial data at the specified baud rate. Over sampling is used in the FPGA to help minimize bit errors.  The serial module passes the raw data to the parser module. At this point in time the raw data is the NMEA messages (with the overhead information removed, i.e. stopbit/startbit). The parser module waits for the occurrence of a '$' which indicates the start of an MTK/NMEA message. Once the '$' is received, the parser extracts the message type and checks for a "GGA" message. If the current message is a GGA message, then we extract the Latitude and Longitude based on the standard format of the GGA message. This is currently being done by counting the characters; however, counting the comma delimiters work just as well. The parser module passes the latitude and longitude data to the LCD module as it is received on the serial line. The LCD controller module handles the initialization process required to set the LCD module into an operative mode, and it handles all the timing and writing data to the display.

This is an on-going project and I plan to add many more features to it. Below are some changes that I plan on making in the future.

Future Improvements/Additions:

• Write the serial stream from the serial module to a Block Memory or RAM
• Read the data in a Block Memory or RAM and feed the data into the Parser Module.
• Perform mathematical operations on the acquired data, such as computing the displacement from the current location to the last saved location.

For those interested in knowing more about this project, or want more information about certain aspects of the HDL code that I wrote, please don't hesitate to post a comment.

For those interested in the LCD controller module's code, go here: LCD Controller.
Or to download all of the related HDL files, go here: GPS2LCD_Files.zip

My project was featured on Sparkfun's Main Page! Pretty cool and I got some good constructive criticism.