Blinky Shield for UNO
This shield adds a LED to every IO-pin of a 'Arduino UNO' or 'Adafruit Metro M4' board (24 LEDs)
A push-button is also connected to pins D2 and D3
In your Sketch: For everything to work well, start the setup() function with a 1-2 milli second (ms) delay.
The reason for this is, that each LED is driven by a separate MOSFET. And the gate pin of each MOSFET is pulled LOW by a 3M3 (3.3 mega ohm) resistor, and after power up, then it takes about 1-2 ms for the state of each pin to settle correctly. This is especially true if the sketch is using the pin for input.
No Blinky on a pin: By removing a jumper, it is possible to completely detach the MOSFET (and the pull-down resistor) from each IO pin - if it for any practical reasons becomes necessary
Technical details: The LEDs for TX, RX, SDA and SCL pins are reversed, because the resting state of Rx, Tx, SDA and SCL is HIGH. And thus it is easier to see the blink, if the LED is Off by default, and only is lit up when data is being transmitted.
A p-channel MOSFET is used for Rx, TX, SDA, SCL pins (these are pulled HIGH). A n-channel MOSFET is used for D0-D13 pins, A0-A5 pins and SPI pins at the ICSP socket (these are pulled LOW).
Project Status: PCB design-verify (rev.C1 - 2023 May 28) - getting ready for the June PCB production batch
Here are some screen shots:
- TOP side
- Bottom Side
Use the PCB viewer if you would like to see/test the entire copper path as it switches sides and/or connects to several solder points.
Inspiration - and more Blinky Shields
Sometimes during sketch development, I want some status indication on pins, and I grew tired of using breadboards, wires, LEDs and resistors - so I have now designed this Blinky Shield - this one is for the 'Arduino UNO' board.
See also a Blinky Shield for 'Wemos D1 mini'