Design based on AT89C4051 digital clock

This is a real-time digital clock made with AT89C405l microcontroller. Due to the use of AT89C405l, this digital clock is very low cost and small in size. It can be made into a small module and is very convenient to use.

1. Hardware design

The figure below is the circuit schematic diagram of a digital clock.

The P1 port of the AT89C4051 microcontroller is used to connect the LCD data line (from pin 7 to pin 14 of the LCD). Use a 20×4 LCD character display.

2. LCD custom character method

In the picture on the right, you can see that the numbers are much larger than the normal font size. For this reason, an LCD with CGRAM (CGRAM is the RAM of the font and character generator, the full name is CharacterGeneratorRAM, or CGRAM for short) is used. Users can flexibly customize characters. . To define a character, first get the value of the character and then write it into the CGRAM area. This CGRAM area starts at O×40, with 8 cells per character. The image on the left is an illustration of a custom character. Therefore, we need to obtain the values ​​of all pixels of the character and write these values ​​into CGRAM. Numbers 0 to 9 can be created with the help of custom 8-shaped characters. Note: Only up to 8 custom characters can be created.

3. Programming

The source code for this production is written in C language and compiled with KeilC. You can download the source code of C. After the source code of C is compiled, you can directly download the hex file to your microcontroller.

4. Production

If you cannot buy the microcontroller in the schematic diagram during production, you can also use AT89C51/AT89C52 instead. But you must ensure that the IO port you use and the port connected to the LCD button are the same as the IO port in the C source code or circuit schematic diagram.

The schematic diagram already contains the power supply part principle.