💡 7Driver

A 4-digit 7-segment LED display driver built on a Saturday years ago, using an ATmega328P Arduino and a couple of spare TTL logic chips (74XX595 and 74XX155). Designed as part of a larger bench ecosystem, this module emphasizes classic hardware logic, multiplexing, and minimal pin usage via serial interfacing.

If you found this project useful, interesting, or worth keeping an eye on, consider giving it a ⭐️. It helps others discover the project and motivates me to keep building and sharing more.

🔹 Rev 1 Schematic

🔹 V1.0.0 For Rev 1

• Tracking versions. Functionally the same.

🔹 Key Features

• Displays numbers on a 4-digit 7-segment LED display
• Built using:
  • 74XX595 – shift register (serial data output)
  • 74XX155 – 2-to-4 line decoder/demux
• Controlled by an ATmega328P
• Segment timing and animation handled in software
• Basic Power-On Self-Test (POST) on startup
• Tested with various counting logic
• ADC input (with potentiometer) for interactive control or display testing

🔹 Design Notes

• RCLK (Pin 12) of the 74LS595 is tied to SRCLK (Pin 11), so outputs update automatically with each bit shifted in — useful for early animation tests.

• Designed to minimize microcontroller pin usage:

  • Serial output via 74LS595 for segment data
  • Digit selection via 74LS155 demux

• Early versions featured:

  • Simple animations
  • Shift speed control using an ADC-connected potentiometer

🔹 General Usage

• Performs a Power-On Self-Test (POST) to verify segment connections and logic IC behavior
• Best used with a regulated 5V supply

🔹 Considered Improvements

• Break out RCLK from SRCLK for controlled output updates
• Add individual resistors per LED segment for more consistent brightness
• Extend character support beyond 0–9 and A–F (e.g., letters, symbols)
• Logic to limit counting to prevent overflow or undefined patterns, so it doesn’t lose its digits ☺️