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Author Topic: Max7219 with 7 segment display using LedControl library  (Read 1120 times)
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Hello,

I have the Max7219 and a common cathode 7-segment display.  The display is from adafruit, http://www.adafruit.com/products/812
I have been looking at the datasheet and hooking it up accordingly to the 7 segment display and then I hooked up the control pins to the proper pins from the 7segment demo example in the LedControl library.

For some reason the last digit isn't lighting up and the digits that are, aren't displaying any legible numbers.  I've checked my wiring 3 times now and it's all proper.  Is there some incompatablility that i'm missing?
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2 things - either you are not telling the library you have 4 digits. Or you do not have the digits wired correctly between the MAX7219 and the display.
We could help if you would post what you have for both.
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The Max7219 can drive 8x 7 segment displays and it numbers the digits 0-7 and the BL-Q56C-43 datasheet numbers the digits 1-4 so this could account for missing digit if it wired this way. Is it wired as below?
Code:
BL-Q56C-43  MAX7219
 1 (E)          21
 2 (D)          23
 3 (DP)         22
 4 (C)          20
 5 (G)          17
 6 (*DIG4)       7
 7 (*COLON)
 8 (COLON)
 9 (B)          16
10 (*DIG3)       6
11 (*DIG2)      11
12 (F)          15
13 (A)          14
14 (*DIG1)       2
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Hmm, I may be just getting confused with the pin mapping of the 7segment display. 
The display has DP segments,  the pins on the side nearest to those DP segements, the left-most one is Pin 1. Correct?
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Hard to say. Use 5V & 1k resistor, another wire to ground. Do some poking around, make sure you know where the pins are.
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Hmm, I may be just getting confused with the pin mapping of the 7segment display.  
The display has DP segments,  the pins on the side nearest to those DP segements, the left-most one is Pin 1. Correct?
When looked at from the front, pin 1 is the bottom left according to the datasheet linked from your first post. There is also a slim possibility the display you have is connected differently (it won't be the first time specifications have change without notice) so follow CrossRoads advice and buzz the pins out to confirm.


* 7 Segment.png (100.41 KB, 924x383 - viewed 53 times.)
« Last Edit: July 26, 2012, 08:32:53 am by Riva » Logged


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