Hello World on LCD HD44780

This is a simple (sarcasm) "Hello world!" project written in Verilog.

The project prints Hello\nworld! string to LCD module compatible with HD44780 specification.

In order to achieve this goal the following modules were developed (copy-pasted from various resources):

• lcd_hd44780.v LCD driver, heavily rewritten sample provided in http://robotics.hobbizine.com/fpgalcd.html
• efifo.v FIFO implementation which allows simultaneous reads and writes, copy-pasted with cosmetic changes from http://www.electrosofts.com/verilog/fifo.html
• lcd_printer.v a custom module which prints the provided input data on LCD using FIFO as a buffer
• debouncer.v a module copy-pasted from https://zipcpu.com/tutorial/ex-07-bouncing.tgz which implements hardware button/switches debounce
• hello_lcd.v prints a string with help of lcd_printer when a switch toggled

NOTE: there is no top file as it will be hardware-depended. In my case hello_lcd instantiation was like:

   hello_lcd top(
                 .user_dipsw(user_dipsw),
                 .clk(clkin_50_top),
                 .lcd_d_c(lcd_d_cn),
                 .lcd_cs(lcd_csn),
                 .lcd_data(lcd_data),
                 .lcd_we(lcd_wen)
                 );

Purpose

This has been written just to play with Verilog while implementing some real-world application. That is why there are several components which can be considered as excessive: LCD module (instead of UART), FIFO (instead of direct write), debouncer.

In practice, FIFO is helpful as printing a string (i.e. for logging purposes) is fast operation while pushing it to real device is quite slow.

Simulation

The project was simulated using Verilator before programming a device. The simulation approach was taken from a great course which inspired me: https://zipcpu.com/tutorial/

For simulation purposes one can find the following:

• hello_lcd_tb.cpp a program which drives the design properly and saves trace which can later be opened with gtkwave
• Makefile compiles the whole project and runs the testbench