LED matrix using shift registers

Step 6 Conclusion

Possible Additions

I2C
I have left the Two Wire Interface (I2C) pins unused in this design. There are several interesting prospects that can use these two pins. Addition of an I2C EEPROM will allow for storage of much larger messages. There is also the prospect of designing programming to turn the mega8 into an I2C compatible display driver. This would open up the possibility of having a USB enable device to display data on your LED array by passing it over the I2C bus.

Input
There are many pins left over that could be used for buttons or an IR receiver. This would allow for messages to be programmed in via a menu system.

Display
For this instructable I only implemented a couple of display functions. One just writes characters to the display, the other scrolls characters onto the display. The important thing to remember is that what you see in the lights is represented in a data array. If you come up with cleaver ways to change the data array, the lights will change in the same way.

Some tantalizing opportunities include creating a graphing meter out of the columns. This could be used as a signal analyzer with a stereo. Scrolling can be implemented from the top down or bottom up, even left to right. Good luck, have fun!

Comments

[jeff-o]

Just to clarify, could I program in a bunch of phrases (like, 30-40) and call up any one of them based on certain inputs? What is the limit on phrase length without any external memory?

[monkeydluffy]

bro barney, can u help me to get HEF4794? i need the HEF4794?? 9 of them to controll my Solar Display. In my country there's no store sell that shift register :( :( Can I get it from u?? I'll pay it later. I'm in Jakarta, Indonesia. Please help me master, this is for my graduation project. thank you very much :)

[memuller]

Can your source code be used with an Atmel 89s52 micro? What should i do, analize the code and change the registers used by the interruptions? Thanks a lot!!!

[barney_1]

I believe you should be able to port this over. You are correct that you need to change the registers to match your pinout. You also need to make sure you have the correct vector names for the interrupts, these can be different between different chips. You also may (and I'm not sure here) have a problem with running out of ram as the mega8 has more than the 89s52 does

[pierrotlf]

This was really helpful. Thanks so much for doing it. I'm not a total novice but you probably saved me from using the wrong hardware and making a mess of things. Only thing I don't understand: can you explain a little more about rationale for the 3.3k resistors? (The schematic I found for the mic2981 shows internal resistors on the inputs, but doesn't give their value). Sorry if I overlooked something or if it's a dumb question. Thanks.

[barney_1]

Looking at the datasheet is seems quite possible that these resistors are not necessary but I'm not certain. Anyone else have an opinion on this?