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Introduction

Freddie's Pad is an In-Line and Extended-Size Shield designed to enhance most Arduino platforms.

Arduino control boards allow accessory boards called "shields" to be installed. Shields provide additional peripherals that can extend the functionality of your existing hardware.

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Details

Widening this shield beyond the typical size made it possible to place Light Emitting Diodes beside each pin they monitor. This offers an easy view of the LED's in many situations. The board is rectangular which lowered the cost of the bare PCB. This shield is not going to fit inside a standard case. You can use the shield by itself, or place more on top of it, making it "in-line". Having five Freddie's Pad shields on one Arduino (attached using the USB method) can be enough to fully load its power supply because of all the LED's.

The shield contains two low-cost Altera MAX 3000 series CPLD's. The Complex Programmable Logic Devices used are the EPM3064ATC-10N. These are 44-Pin TQFP devices with 64-Macrocells. They can operate at speeds much faster than an Arduino Atmel microcontroller. Both devices are programmed uniquely to effectively show digital activity.

Each Arduino signal is wired to a PLD input pin. For each signal, a corresponding PLD output pin is then wired in series to a resistor and LED to the +3.3 Volt power rail.

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Two green LED’s indicate the static presence of +3.3V and +5V power supplies. Twenty-one LED’s indicate status for these digital signals:

Port B:  B0, B1, B2, B3, B4, B5 (six)
Port C:  C0, C1, C2, C3, C4, C5 (six)
Port D:  D0, D1, D2, D3, D4, D5, D6, D7 (eight)
Reset# (red LED, active low# is ON when low, means CPU is in reset)

When activity occurs on any signal, you will be aware of it. It’s like having an oscilloscope on each pin, set to trigger all the time!

Digital signals change states so fast at times that a simple LED circuit will not show what is happening. Freddie's Pad shows two conditions:

Logical low (zero Volt or Ground level)
Logical high (positive 3 to 5 Volt level)

Freddie's Pad monitors each signal and detects state changes as they happen.

When triggered by a fast changing signal, a slower response is generated enabling activity to be observed:

LED is OFF when signal is LOW
LED is ON when signal is HIGH
(Note: Reset# activity line is inverted)

Response period is long enough for your eye to identify the change.

Any additional state changes during a response period are ignored.

Who needs such a shield board?

People interested in understanding both software and hardware.

Freddie's Pad is an excellent tool for your collection.

What makes this shield special?

Freddie's Pad can be a tremendous value when developing and testing.

It offers the ability to know when and how often serial communication ports are active, and what state each of the signal pins are at. See how some of your favorite sketches behave by adding Freddie's Pad to your Arduino project.

You can see a short video clip of Freddie's Pad in action at: https://youtu.be/EfBAB40wDlw.

This demonstration and promotional clip shows a tutorial using a color TFT shield installed on top of Freddie's Pad. The tutorial shows an example of how 8-bits are used to count in binary, decimal and hexadecimal.