LCD drivers

I am considering using an MCU that has built in LCD drivers, but it only implements 1:8 multiplexing. In other words, it has eight "common" lines that are sequentially asserted. I need to connect it to an eight character seven segment display. None of the displays that I have found are designed for 1:8 multiplexing. Is it possible, and reasonable, to use this MCU with a display that only has four commons (1:4 multiplexing)? If so, would I use four consecutive commons, or every other one? Would the appearance suffer in any way? And what if the display is 1:3?

Thanks for any help. Howard Delman

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Delman Design
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Howard Delman
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Of the CPUs that I've seen, they can be programmed for 1:1, 1:2, 1:4, and 1:8.

It would really help us help you if you would just tell us what you are using, instead of letting us guess.

Reply to
Donald

I am considering the Elan EM78869. It only allows 1:8 or 1:9. It has more than enough segment drivers.

I've designed a handful of products with LCDs, and I know well how to use them. What I have no experience with is using an LCD with a mis-matched driver. I am hoping that someone on this list does.

Howard

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Howard Delman

I found this:

formatting link

I would guess that this chip was designed for a specific customer before it was released to the public. Which means the specific customer had a specific LCD display they were using.

As you seem to well know, LCD glass is brain dead simple. All the work is done in the LCD controller. So, I think you need to find a 8 or

9 common LCD display.

I wonder if this would make the display fab cheaper than say a 4:1.

Donald

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Donald

Thanks for the link, but I already have all of the information on the processor. In fact, I have been in contact with an FAE at Elan in China. What I don't have is a good answer to my question. The Elan FAE recommends that I buy their emulator, build it, and try it, but I don't have the time. I am bidding on a contract, and I really need to nail down my processor before I can submit the bid. This is a high volume, low cost, consumer product, in which a few pennies is a significant amount. Otherwise, I would just go with a custom display to match the processor. Low price is what makes the Elan processor so attractive.

Howard

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Howard Delman

I don't think it will work acceptably unless you can source a matching LCD display.

Do some calculations of the RMS segment voltage in each case and compare for yourself.

Best regards, Spehro Pefhany

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Spehro Pefhany

I whole heartly agree here.

If the volume is really that high, the limiting cost would be the long lead items. And I bet its the LCD.

Time is also money, We all know the curve, the later the delivery the later the tapping of the market share and lost revenue.

Something I keep lossing track of " KIS " ; keep it simple.

donald

Reply to
Donald

Thanks for the help, guys. I suspect you are both right.

In this case, time is more than just money. It could be the entire contract. If I don't submit this within a week, it won't happen at all. That's why I can't get the emulator from China and try it out.

Howard

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Delman Design
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Howard Delman

I read in sci.electronics.design that Howard Delman wrote (in ) about 'LCD drivers', on Sun, 2 Oct 2005:

How much to get it air-couriered from China? Quite a bit, no doubt, but as a percentage of the contract?

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John Woodgate

It not just shipping time. This is not like dealing with amazon.com. I can't just pick up the phone and have one sent the next day. It would take a couple of weeks to get the order through the system, get the funds wired to Hong Kong, clear customs, etc. And then I have to get the system installed here, learn how to use it, etc.

Howard

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