LEARNING
TO MAKE

Week 13: Output Devices

Task

The task is to add an output device to a microcontroller board you've designed and program it to do something. I continue with the prototype for my final project. I will add 5 LEDs to my helloworld board & shield. The goal is to light the LEDs up according to the intensity of the signal of the galvanic skin sensor.

References

* Here is the content page and Neil´s lecture video.

Process

In order to extend my helloworld board I checked which pins on the ATTiny 44 are still free. I connect the LEDs to PB2, PA2, PA3, PA4, PA5 through a header and via "under board" cables by drilling tiny holes in the board. The cables function like cupper traces. An additional connection links the header/the LEDs with GND. For the code the pins need to be re-translated to Arduino. Here is a sketch:

I do not use TX and RX as these pins are needed for the communication between the board and the computer. While I do not need this communication capability for this assignment, I need it in my final project. The filled out pins will be used for the LEDs. Also indicated is the trasnlation between AtTiny44 and Arduino pins. Excuse the handwriting catastrophy ; )

The wired board. Admittedly not the prettiest prototype ; )

Schemantic & Traces

Next I made the schemantic and traces of the LED PCB board in Eagle and prepared the files in Gimp for milling. The board has 5 LEDs, 5 corresponding resitors (499k) and a header. Each Led connects to one pin, all LEDs connect to GND.

LED board design

LED board ready to mill

the milling bit was no good, but believe it or not, this started as a beautifully soldered board. I was already happy about my improvement of skills - until I noticed that I had misplaced all my components, being in a hurry and all. Heat gun & redo created this.

hello world board, shield, LED addition all mounted

Pin Placements for LEDs

* PA2 (Arduino A2) - LED 1
* PA3 (Arduino A3) - LED 2
* PA4 (Arduino A4) - LED 3
* PA5 (Arduino A5) - LED 4
* PB2 (Arduino 8) - LED 5

code for the blink test, example Pin 8

First Test: Arduino blink

* PA2 (Arduino A2) - LED 1: LED 2 is on
* PA3 (Arduino A3) - LED 2: LED 4 blinks, turns off
* PA4 (Arduino A4) - LED 3: LED 4 blinks, turns off
* PA5 (Arduino A5) - LED 4: LED 4 blinks, then stays on
* PB2 (Arduino 8) - LED 5: LED 5 is on

Blink Troubleshoot

* checked connections with multimeter, worked
* realised had used 499k resitors. desoldered, replaced with 100ohm; double check direction LED is soldered on board.
* Ferdi´s hack: cut trace connection between on-board button and it´s resitor to use pin only for LED

Second Test: Arduino blink

* PA2 (Arduino A2) - LED 1: LED 1 glows weakly, LED 2 is on
* PA3 (Arduino A3) - LED 2: LED 1 is on
* PA4 (Arduino A4) - LED 3: LED 1 glows weakly, LED 3 is on
* PA5 (Arduino A5) - LED 4: LED 1 glows weakly, LED 4 is on
* PB2 (Arduino 8) - LED 5: LED 1 glows weakly, LED 5 is on

Blink Troubleshoot

* rechecked pin - LED connections, LED1 is PA3 not PA2; LED2 is PA2 not PA3; others are correct
* new code: blink through LEDS: all working except LED5 due to broken solder connection; resoldered it and now it works - finally.

new and final code for the blink through LEDs test

Result: muy bien

5 LEDS Blink week 13 from Norma D. on Vimeo.

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