Post by thread:Driving LCDs

I'd appreciate any suggestions on inexpensive LCD drivers to use with a PIC. I'm building an exercise computer with three 4 digit LCDs (7 segment). I think that's too many to drive directly with the PIC, and the PIC with a built-in LCD driver is expensive (and I guess I'd need one for each LCD). I'm thinking of a 16F84 controlling three LCD drivers or maybe one driver multiplexed amoung the three LCDs. This is my first project using LCDs (for low power) and the blasted things seem more complicated than LEDs. Which drivers and method make sense to use? I am so consumed with designing this that I've given up exercising until it is done. I'm turning to fat even as you read this. Please help. _________________________________________________________ DO YOU YAHOO!? Get your free @yahoo.com address at http://mail.yahoo.com

Hi I have the same problem with my project "talking clock" my advice is use LED instead of LCD if you want to use LCD you must know that it require a backplane strobe pulse to keep the display refreshed, otherwise it'll go blank. This is more difficult to impliment with the PIC because you really need to use interupts to keep regular pulses so that the displays don't flicker. by the way I would be interessted if you solve the problem do email me back you have some tip for my project sam ______________________________________________________ Get Your Private, Free Email at http://www.hotmail.com

At 10:30 AM 1/18/98 -0800, you wrote: >I'd appreciate any suggestions on inexpensive LCD drivers to use with >a PIC. I'm building an exercise computer with three 4 digit LCDs How about the AY0438? It is like the LCD driver PIC without the PIC. $4 at DigiKey, or thereabouts. Made by Microchip, even. -bob http://www.bobblick.com/

> My advice is use LED instead of LCD. > If you want to use LCD you must know that > it requires a backplane strobe pulse to > keep the display refreshed, otherwise > it'll go blank. Yeah, but almost nobody actually bothers to drive an LCD _directly_. For a four-digit seven-segment LCD with one backplane I would use an MM5452 or MM5453, which drive 32 and 33 LCD segments respectively. These chips require only a resistor and capacitor (to produce the backplane strobe), and have a two-line interface to the micro- controller (clock and data). The comms protocol is trivial. For a four-digit seven-segment LCD with two backplanes I would use a PCF8577, which can drive up to 64 LCD segments. Again, only an RC pair is required, and the two-line interface is now IIC! This allows the chip to share the comms bus with other devices (including other '8577s). The comms protocol is no longer trivial, but IIC software is readily available. As I recall, the original mailer needed to drive three LCD's... With '5453s this would require three chips, and they can't be connected to the same two clock and data lines. They could share a data line, but would all need seperate clock lines. This gives a total of four I/O lines required. With '8577s (and assuming static drive LCDs, that is, one backplane) three chips would again be needed. But in this case all three chips could be connected to the same two-wire IIC bus and separately addressed. So only two I/O lines required. Go to http://www.semiconductors.philips.com/search/ to search for the PCF8577 data sheet (.pdf). ___Bob

Rock wrote: >I'm building an exercise computer with three 4 digit LCDs (7 segment). I think >that's too many to drive directly with the PIC, and the PIC with a built-in LCD >driver is expensive (and I guess I'd need one for each LCD). I have used the Telcom TC7211 chip a long time ago. It is a four-digit 7-segment LCD controller. I believe that MAXIM is now making (or at least second-sourcing the chip) as ICM7211. I've no idea on the price, but I have used these and the ICM7218 (8-digit 7-segment LED Mux/Decoder/Driver) with success. It (the `7211) uses a four-bit data bus and four seperate digit select pins. Of course you could reduce the pin count by two using some logic circuitry between two pic pins and the four select lines. The data sheet in PDF format can be found at: http://209.1.238.250/arpdf/1675.pdf Best of luck on your reducing program! ;^) Michael /******************************************************************************* \** When the way of the Tao is forgotten, kindness and ethics must be taught. ** ** Men must learn to pretend to be wise and good. -- Lao Tzu ** \******************************************************************************* /

Rock Thompson wrote: > > I'd appreciate any suggestions on inexpensive LCD drivers to use with > a PIC. I'm building an exercise computer with three 4 digit LCDs (7 > segment). I think that's too many to drive directly with the PIC, and > the PIC with a built-in LCD driver is expensive (and I guess I'd need > one for each LCD). > > I'm thinking of a 16F84 controlling three LCD drivers or maybe one > driver multiplexed amoung the three LCDs. > This is my first project using LCDs (for low power) and the blasted > things seem more complicated than LEDs. Which drivers and method make > sense to use? > > I am so consumed with designing this that I've given up exercising > until it is done. I'm turning to fat even as you read this. Please > help. > _________________________________________________________ > DO YOU YAHOO!? > Get your free @yahoo.com address at http://mail.yahoo.com I have done for PIC16F84 (I used the Tango for D.O.S for the Schematic) (PIC16F84 WITH FOUR 7 SEGMENT DISPLAYS) Do you want? :))) MIGUEL.

sam Haile wrote: {Quote hidden}> > Hi > I have the same problem with my project > "talking clock" > > my advice is use LED instead of LCD > if you want to use LCD you must know that > it require a backplane strobe pulse > to keep the display refreshed, otherwise it'll go blank. This is > more difficult to impliment with the PIC because you really need to > use interupts to keep regular pulses so that the displays don't flicker. > > by the way I would be interessted if you solve the problem > > do email me back you have some tip for my project > > sam > > ______________________________________________________ > Get Your Private, Free Email at http://www.hotmail.com I resolved the Flick with computed delay! Miguel.

I would appreciate a copy of TANGO schematic and PIC code. Also are you still using TANGO DOS or have you switched to something else. I am trying to decide what to switch to. Mike Montaigne {Quote hidden}> ---------- > From: WF AUTOMACAO[SMTP:spam_OUTwfTakeThisOuTAMBIENTE.COM.BR] > Sent: Monday, January 26, 1998 1:51 PM > To: .....PICLISTKILLspam@spam@MITVMA.MIT.EDU > Subject: Re: Driving LCDs > > Rock Thompson wrote: > > > > I'd appreciate any suggestions on inexpensive LCD drivers to use > with > > a PIC. I'm building an exercise computer with three 4 digit LCDs (7 > > segment). I think that's too many to drive directly with the PIC, > and > > the PIC with a built-in LCD driver is expensive (and I guess I'd > need > > one for each LCD). > > > > I'm thinking of a 16F84 controlling three LCD drivers or maybe one > > driver multiplexed amoung the three LCDs. > > This is my first project using LCDs (for low power) and the blasted > > things seem more complicated than LEDs. Which drivers and method > make > > sense to use? > > > > I am so consumed with designing this that I've given up exercising > > until it is done. I'm turning to fat even as you read this. Please > > help. > > _________________________________________________________ > > DO YOU YAHOO!? > > Get your free @yahoo.com address at http://mail.yahoo.com > > I have done for PIC16F84 (I used the Tango for D.O.S for the > Schematic) > > (PIC16F84 WITH FOUR 7 SEGMENT DISPLAYS) > > Do you want? :))) > > MIGUEL. >