Post by thread:32 bit rotate

Hi everyone, I'm trying to find a way of displaying a message in a 5x7 LED array. Basically, I don't have a good idea of how this is usually done, but since I have worked a little bit with the 16C84, I thought I give it a try. I was thinking about having a message array 32 bits long by 5 bit wide containing the information I want to display. I would then take each one of the 32 bit words and rotate sequentially bit by bit and display the 7 most significant bits after each rotation. I would do this for each of the 5 rows of the LED display. I will appreciate any help on how I do this 32 bit rotation with the PIC, and also any suggestions or comments as of how messages can be displayed in LED display arrays with the PIC. Best Regards, Pedro

Pedro Barrios wrote: > I'm trying to find a way of displaying a message in a 5x7 LED > array. The "Times Square" display thread re-surfaces! > I was thinking about having a message array 32 bits long by > 5 bit wide containing the information I want to display. Which way up is the display? Usually the 7 vertical and the 5 horizontal. As such, you have described a vertical message stripe. Surely not? Or are you going to use it on its side, only five bits high? > I would then take each one of the 32 bit words and rotate sequentially > bit by bit and display the 7 most significant bits after each > rotation. I would do this for each of the 5 rows of the LED display. A way of driving a *single* 5 by 7 display, is to use an 8-bit shift register (e.g. 74HC164) into which a column of 7 bits is loaded, the column multiplexer is disabled, the latch in the SR is updated and the new appropriate column enabled by multiplexer. If you're really cunning, do the column multiplexing with an HC4022 octal counter/decoder whose clock is the latch enable and reset is the eighth bit of the shift register. Result: 3-bit interface to the PIC (data, shift clock, latch). Code to do this and read character tables? Well, best describe exactly how you wish to view or scroll and what characters, first? Cheers, Paul B.

> Van: Pedro Barrios <spam_OUTbarriosTakeThisOuTnanofab.physics.tamu.edu> > Aan: .....PICLISTKILLspam@spam@MITVMA.MIT.EDU > Onderwerp: 32 bit rotate > Datum: dinsdag 9 juni 1998 20:59 > > Hi everyone, > > I'm trying to find a way of displaying a message in a 5x7 LED > array. Basically, I don't have a good idea of how this is > usually done, but since I have worked a little bit with the > 16C84, I thought I give it a try. > > I was thinking about having a message array 32 bits long by > 5 bit wide containing the information I want to display. I would > then take each one of the 32 bit words and rotate sequentially > bit by bit and display the 7 most significant bits after each And see a dark line every 8 leds (horizontal) ? I would not do that. Just shift every line (of 4 * 8 bits) one bit to the left. you could shift the new data (one bit) in when shifting the right-most byte. Repeat this for every line. > rotation. I would do this for each of the 5 rows of the LED display. > I will appreciate any help on how I do this 32 bit rotation with > the PIC, and also any suggestions or comments as of how messages > can be displayed in LED display arrays with the PIC. > > Best Regards, > > Pedro A 32-bit rotation (Left) : movwf {data to shift in} rrf {data to shift in} rlf {line1+3} rlf {line1+2} rlf {line1+1} rlf {line1+0} rrf {data to shift in} rlf {line2+3} rlf {line2+2} rlf {line2+1} rlf {line2+0} etc. {data to shift in} contains 5 bit of data. Bit 0 is the bit shifted into line #1. Bit 1 is the bit shifted into line #2. etc etc etc. {Line1+3} is the right-most byte to be displayed (bit 0 at the right-most position, bit 7 at the left-most). Greetz, Rudy Wieser P.s. Need more info ? Just tell me.

Hi Rudy, Why do you think I'll be seeing a dark line. I think that as long as the 8 bit word keeps shifting a bit at a time, I'll always be able to see the entire message. {Quote hidden}>> I'm trying to find a way of displaying a message in a 5x7 LED >> array. Basically, I don't have a good idea of how this is >> usually done, but since I have worked a little bit with the >> 16C84, I thought I give it a try. >> >> I was thinking about having a message array 32 bits long by >> 5 bit wide containing the information I want to display. I would >> then take each one of the 32 bit words and rotate sequentially >> bit by bit and display the 7 most significant bits after each > >And see a dark line every 8 leds (horizontal) ? I would not do that. >Just shift every line (of 4 * 8 bits) one bit to the left. you could shift >the new data (one bit) in when shifting the right-most byte. Repeat this >for every line. Why are you using the rrf instruction? {Quote hidden}>A 32-bit rotation (Left) : > >movwf {data to shift in} >rrf {data to shift in} >rlf {line1+3} >rlf {line1+2} >rlf {line1+1} >rlf {line1+0} >rrf {data to shift in} >rlf {line2+3} >rlf {line2+2} >rlf {line2+1} >rlf {line2+0} > >etc. > >{data to shift in} contains 5 bit of data. Bit 0 is the bit shifted into >line #1. Bit 1 is the bit shifted into line #2. etc etc etc. ^ | What 5 bits here are you talking about? {Quote hidden}> >{Line1+3} is the right-most byte to be displayed (bit 0 at the right-most >position, bit 7 at the left-most). > >Greetz, > Rudy Wieser > >P.s. > Need more info ? Just tell me. >

> Van: Pedro Barrios <barriosKILLspamnanofab.physics.tamu.edu> > Aan: .....PICLISTKILLspam.....MITVMA.MIT.EDU > Onderwerp: Re: 32 bit rotate > Datum: woensdag 10 juni 1998 21:22 > > Hi Rudy, > > Why do you think I'll be seeing a dark line. I think that as > long as the 8 bit word keeps shifting a bit at a time, I'll > always be able to see the entire message. I thought you had a 5 high and 7 wide char, and would display it on a 5 * 8 (* 4 chars) display, thus never using every 8th (vertical) row of leds. I got confused ... [Cut] > Why are you using the rrf instruction? The byte in the W register is one (1) vertical line of data. Bit 0 contains the top-most bit of your character, Bit 1 the bit below the first, and so on. This means that bit 0 should be shifted in into line #1 (horizontal), bit 1 into line #2, etc. By way of shifting to the right the bits (formerly in the W register) will be shifted into the Carry, and than can be shifted into the apropriate line. [Cut] > >{data to shift in} contains 5 bit of data. Bit 0 is the bit shifted into > >line #1. Bit 1 is the bit shifted into line #2. etc etc etc. > > ^ > | > What 5 bits here are you talking about? As I said, I was thinking about a 5 high and 7 wide character. wich is, at best, not very readable .... [Cut] Greetz, Rudy Wieser