The motivation for this project was partly that I needed one for debugging more complicated projects, and partly that I wanted to explore some of the new features of the AVR DB series.
The Hex Logic Level Detector uses all of the AVR128DB28’s IO-pins in the prototype-friendly 28-pins DIL package.
This construction goes hand in hand with my Hex Logic Generator project (see link).

Features
-Six logic channels.
-Logic levels: Low, high, or floating displayed by red and green LEDs
-Edge detection: Blue LEDs flash when level changes
-Channels 2, 3, 4 & 5 detect pulses as short as 25 ns. (Channels 0 & 1: 50 ns)
-Supply voltage span: 2.5 – 5.0 V (UB – MCU and channels 3, 4 & 5)
-Three channels can optionally operate at different voltage: 1.65 – 5.0 V (UA – channels 0, 1 & 2)
-System resets when primary supply voltage is too low (UB < 2.45 V)
-Indicator for insufficient secondary supply voltage (UA < 1.65 V)