In this post a basic character generator design based on PIC16F88 will be demonstrated. 7×5 Dot Matrix Display was used and its pin out is shown in the schematic below. Instead of using PIC16F876/7 microcontrollers PIC16F88
was chosen for this purpose. It has a smaller pin count but still has a sufficient number of I/O for driving the display and supports a number of serial interfaces like SPI,I2C for future upgrades. Another advantage of PIC16F88 MCU is a built in oscillator that further simplifies the circuit. Next figure summarizes currently supported characters. Multiplexing routine gives you an ability to individually control each dot in the array, so additional symbols can be added/created. In order to show different characters modify the code by calling a symbol function. For example call Show7 will output 7 on the Display. See assembly code for additional info at the bottom of the page.
Design schematic and prototype board are shown next. They are as simple as they can be, except for microcontroller and display no additional components are required.
Click this link for Character Generator Assembly code. More advanced generator design with serial communication can be found in this post. Similar project about interfacing 7×5 Dot Matrix LED Display can be found here.