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Topic: Max7219 with 7 segment display using LedControl library (Read 1 time) previous topic - next topic

funkyguy4000

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?
Accelerate to 88 miles per hour.

CrossRoads

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.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

Riva

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: [Select]
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

funkyguy4000

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?
Accelerate to 88 miles per hour.

CrossRoads

Hard to say. Use 5V & 1k resistor, another wire to ground. Do some poking around, make sure you know where the pins are.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

Riva

#5
Jul 26, 2012, 08:47 am Last Edit: Jul 26, 2012, 03:32 pm by Riva Reason: 1

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.

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