In SX Microcontrollers, SX/B Compiler and SX-Key Tool, tdg8934 wrote: Zoot, I had a couple of home emergencies Monday so haven't been too active on this project. 1. Hit a deer so my Ford Explorer is messed up in the shop - thank God for insurance / rental car, etc. 2. My 50" Sony TV stopped working - Cycles power off and on every 30 seconds. Weird. However, here is my latest correspondance with SparkFun Support: [color=#000000]Chris,[/color] [color=#0066cc>mailto:chris@sparkfun.com] Sent:]To: Gilmore, Timothy Subject: Re: [Fwd: [Fwd: [Fwd: Re: Return 2 Large RGB LED Matrix and controllers & minor associated components]]] Mr. Gilmore, Sorry if that was a bit vague. The way I have it set up, the DATA IN, CS, and CLK from the controller (I'm using a n LPC2106 from Olimex) are sent to a buffer, which sends the signal to the LED matrix just via the matrix's header. Then the DATA OUT from that matrix is sent to the next buffer, and then from the buffer to the next matrix's DATA IN line. This goes on through the whole array, and then the DATA OUT from the last matrix is sent all the way back to the controller. So in essence, there is a buffer in between each matrix, not on the matrix board itself. I am buffering CS and CLK all the way down the array, so that each matrix sees the same signal. A standard buffer or P-FET should work, as long as they are fast enough for your application. I also have 100uF caps on the power line near each matrix, just to be sure that I don't run into noise issues. -Chris Gilmore, Timothy wrote: > Chris, > > Thanks for the analysis work. When you say the data lines, can you be > more specific? As this backpack device is serial it only has 3 or 4 > "accessible" lines being CLOCK, DATA IN, (DATA OUT) and CHIP SELECT. > > Or are you referring to the DATA lines between each of the 74LS595's and > the RGB LED's on the backpack itself? This may not be that feasible and > sort of defeats the purpose of the "plug in" backpack to the LED module. > I tend to use ULN2803's for buffers (or P channel MOSFETs) on other > projects. Is this what you are implying? > > Tim > > > > > > -----Original Message----- > From: Chris Taylor [[url=chris@sparkfun.com][u]mailto:chris@sparkfun.com[/color][/u][/url]] > Sent: Tuesday, October 30, 2007 12:14 PM > To: TIMOTHY.D.GILMORE@saic.com; spark@sparkfun.com > Subject: Re: [Fwd: [Fwd: [Fwd: Re: Return 2 Large RGB LED Matrix and > controllers & minor associated components]]] > > Hi Mr. Glimore, > I am actually working on a very similar project. The ghosting you're > seeing is due to signal integrity issues with the data lines. Sounds > like your power supply is adequate. I have an array of 8 LED boards > scrolling messages and patterns. I solved the signal integrity problem > by buffering the data lines each step of the way with simple drivers. I > used a 7HCT365 for the buffer, and it worked well for me. > > -Chris

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