I have made a display using a shift-solution... I made it up of modules. Each module is 8x8 and perfectly squared. I have one main-board that has a 16F84 running at only 4 MHz. The others only have shift-registers and led's. The system is organized with D-sub's on both sides so that u can connect them together. I designed the board-layout so that there will be no anomalies in the led-spacing when adding boards. This design uses 8pcs. 8-bit shift registers. One for each row. The data in/out is connected to the next card through the connectors. Theese also transfer a reset signal and power. I also have a signal going back again through the chain by adding a terminator to the last card. Thereby allowing the master-card to determine the with of the display at power-up. (by counting bits) Since my design uses the shift-registers to sink current from the leds to turn them on, it uses more power that a strobing solution. It will instead allow filming without flickering, wich was why I made it this way. Also, for simple scrolling text, u can use a super-low clock-speed. My components can take a clock-speed of 25 MHz and I have tested the design at this speed and found no corruption of the text. This means that if u want to do some more fancy stuff then just scrolling one way, this can be done by clearing and shifting a new image in from the master-card. The power-rails in my design can handle about 3 amps with all power delivered in daisy-chain by the master-card.. This will give a max display width of about 2-3 meters. This should be enough :-) The design is simple and cheap. It will work even better with a single 8x8 matrix cuz then u will have less data to deal with and less time spendt in updaing display. at 25 MHz u could replace the 8x8 image in only 320 ns. This will be so fast that the leds won't even visibly light up before data has passed them. I have tested this with a 32x8 array and 4 pinwheels rotating on the display. Updates then took 1.28 us and the led's were lidt for almost 125 ms giving 8 fps. (For this I used the image stored in ram, and just fed the display a new block every 125'th ms. (To test 25 MHz shift frequency) Looked kinda cool :) KreAture ----- Original Message ----- From: "Jinx" To: Sent: Monday, August 20, 2001 12:43 AM Subject: Re: [PICLIST] [EE]: LED Matrix : there's got to be a cheaper way? > > OK, I want to have control over every dot, instead of using > > each matrix to build an individual character... > > So you're talking bit-mapping ? Use two 74HC164 shift registers > on each matrix - one for column, one for row. Now, if you have a > number of matrices and just one micro suppling data to all pairs > of SR's you may have a problem with timing overhead. The micro > may be just too busy to refresh the pixels comfortably. In which > case you should consider a small micro (508/84/628) to do the > donkey work for its assigned matrix and use your larger micro > to supervise. To get the best out of the display it's going to come > down to timing - if you start compromising and the end result > looks like a piece of crap, was it worth saving a few bucks ? > > -- > http://www.piclist.com hint: To leave the PICList > mailto:piclist-unsubscribe-request@mitvma.mit.edu > > -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu