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.