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Alphanumeric LEDs w/ only 7-data lines and 4-mux select.

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DaKandEKid

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I bought some Alphanumeric LED displays which only have 7 data lines and 4 mux. They have less i/o lines then typical alphanumeric led displays.

https://www.electro-tech-online.com/custompdfs/2004/10/MDA6141C6341C6441C6941C.pdf

If you look at page 3 on the datasheet above it shows you the schematic for the display. Now say for example you wanted to display a 3 on digit 1 of the display.

You would have to set the following segments high: A1 B2, C2, A2, D2

The cathodes are bused so if i set the Cathode 1 low it would turn on all segments which have the Anode set high. So, the problem is since i need to turn on A1. It forces me to have to turn on B1, C1, and D1 as well since the B, C, and D segments are set.

Therefore, I guess the only way to make most characters is to do them in two passes. One where all the digit one segments are set and then another where just the digit two segments are set.

I was unable to find any information about this type of LED display and was wondering if anyone could confirm that this is what you're supposed to do or if i was just missing something obvious and it's not that complicated.
 
Multiplexed 'Starburst' displays

You are sort-of right ...
in order to keep the pin-count low the manufacturers have multiplexed both characters (left and right) and halves (upper and lower). To give a simple digit select would require two common cathodes and fifteen segment selects - 17 pins, this layout requires only 13 (wow- big deal!) - as there are only seven segment lines (ignoring DP selects) it can be driven by an octal driver?

The way to use it is -
set up the left hand side of your first character then pull the first common cathode (pin 15) low;
wait;
cancel the first common cathode and set up the right hand side of the first character then pull the second common cathode (pin 5) low;
wait;
cancel that common cathode and set up the left hand side of the second character then pull the third common cathode (pin 8) low;
wait;
blah-blah

The 'wait' bits are to give each segment enough time energised to let you see them- maybe a 1/10th of a second ? - the usual persistence of vision stuff.
 
i have looked for some sort of special driver for this part of course fairchild has nothing..
 
yeah i found it kind of rediculous that the datasheet didn't have any information about how this display was supposed to be used.

Trying to find images of how each character should look is pretty hard to find. What i mean is some type of reference for what an A, B, C... etc looks like cause some of the characters are kind of interesting like how the D and B are made.

If anyone has a good link on that let me know.
 
Starburst driver

Try looking at **broken link removed**

If you search for 'starburst driver' or '14 segment driver' there are a few.
 
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