Led display to go 16 x 40

My next step with the LED Array panels will be to make it double tall (16 x 40).  However to do this, I will have to double my row control lines from 8 to 16 while still providing output for the clock and data lines.

The ATMEGA328P I’m using doesn’t have enough I/O while still leaving the chip setup as a Nerdkit Based platform.  For those of you unfamilliar with NerdKits, they offer a beginner package to get people started in micro-controllers.  They also have a great forum of users who are often very helpful.  You can find them at NerdKits.com.

I  have but three options.  I could break from the common platform used in the NerdKit and re-purpose some pins, or I could use a different micro-controller with more I/O (again breaking from the Nerdkit platform), or I could add more circuitry to decode a 4 bit binary row address into a 16 bit output.

I opted for the latter.  I have purchased some 3 to 8 decoders (I’ll cascade two of these to make a 4 x 16), and some octal inverters (the decoders have a low output and I need a high for the display).  Once thes parts arrive, I’ll play with the code to see what happens.

One last note, if anyone is attempting to build these.  I never really defined the connections from the display to the various components.  Here are the connections for the prior two setups (8×40 and 8×80):

  • PB3 to 75183 Pin10 (Clock)
  • PB5 to 75183 Pin4 (Data)
  • PC0 to J1 Pin2 (Row 1 Enable)
  • PC1 to J1 Pin3 (Row 2 Enable)
  • PC2 to J1 Pin4 (Row 3 Enable)
  • PC3 to J1 Pin5 (Row 4 Enable)
  • PD4 to J1 Pin6 (Row 5 Enable)
  • PD5 to J1 Pin7 (Row 6 Enable)
  • PD6 to J1 Pin8 (Row 7 Enable)
  • Pd7 to J1 Pin9 (Row 8 Enable)
  • 75183 Pin5 to J1 Pin14 (Data High Input)
  • 75183 Pin6 to J1 Pin13 (Data Low Input)
  • 75183 Pin8 to J1 Pin12 (Clock Low Input)
  • 75183 Pin9 to J1 Pin11 (Clock High Input)
  • Connect Pin7 of 75183 to Ground and Pin14 to VCC
  • Connect Jumpers between Pins 1, 2, 3, & 4 of 75183
  • Connect Jumpers between Pins 10, 11, 12, & 13 of 75183
  • Connect ground wire between breadboard and all ground connections of display to establish a common ground.
  • Connect 5V from microcontroller circuit to 5L on display
  • Connect Higher current 5v (I’m using a 2.5A supply) to 5D on display.
  • Connect ground of both supplies to common grounds.

Do not apply power until ALL connections are verified.  I am not responsible if you connect something improperly and damage your display, microcontroller, or all of the above.

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