The Chips are: 74HC164 (Cheap but no seperate strobe line) 4094 (Costs slightly more but works great) 74HCT595 (Just as good as a 4094 maybe even better) For a all you need to do is shift out the data one bit at a time and toggle the clock pin. 4094 and 595 need an extra pin for loading. After shifting out the whole pattern, you set the load pin and all the output latches are loaded with your shifted value. I personally use and prefer 595s. I use it in an application to drive 4 7seg displays from a 16f84 using one 595 and 4 PNP transistors(to enable the common cathodes selectively). Works clean and reduces the PIN count drastically. You could also chain these ICs to form a long chain of outputs using only 2 or 3 pins on the PIC. I got this idea from the CIO library in JAL. Regards, Jeethu Rao > -----Original Message----- > From: pic microcontroller discussion list > [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Kathy Quinlan > Sent: Sunday, August 19, 2001 11:12 PM > To: PICLIST@MITVMA.MIT.EDU > Subject: Re: [EE]: LED Matrix : there's got to be a cheaper way? > > > Why not just use a ripple latch for each column and send the data > "serially" > ? > > The data is sent as a continuous stream, and a clock shifts the > bits in and > out, and each bit comes out when an "update command" is issued > > I can not remember the chip # but it is a common 74 or 40 serries > latch with > serial in and parallel out. > > Regards, > > Kat. > > > ----- Original Message ----- > From: "rad0" > To: > Sent: Monday, August 20, 2001 12:32 AM > Subject: Re: [EE]: LED Matrix : there's got to be a cheaper way? > > > > > How about a couple latch chips (a column select latch and row > latch) and > a > > > for each character and updating to the next column on every sweep? > You'll > > > probably want transistors to better drive them. Even a 0.7" > LED matrix > > taht > > > I am using is almost begging for transistors, right now it is directly > > > driven by an 'F872, I am not using multiple displays. > > > > > > There are tricks to save here and there but a large set of > LED matrices > is > > > going to cost you. > > > > > > Jeff > > > > Thanks > > > > how would I catch the serial bytes that I am sending out to each matrix? > > > > is there such a thing as a latch that has a serial input? > > > > > > with a pic, I want to use 3 lines to each matrix, ground, pwr, and > serial... > > > > and these could be common to all...each matrix listening for > it's address > > and > > ignoring everybody else... > > > > -- > > 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 > > -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads