MadeInTheUSB: September 2015

Sunday, September 27, 2015

ATtiny85 and Adafruit NeoPixel

If you decide to program an ATtiny85 to control Adafruit NeoPixel, it may be necessary to reset chip fuse to 8 Mhz.
I bought ATtiny85-20PU from mouser.com. This chip has an internal clock and can do 1 Mhz and 8 Mhz.
I believed it is shipped set to 1 Mhz, which will not work with the Adafruit NeoPixel.

Here are a few reminders.

Download Arduino 1.6 or greater

Installing the ATiny85 configurations in the Arduino IDE

Click File -> Preferences and enter the following url in field Additional Boards Manager Urls

https://raw.githubusercontent.com/damellis/attiny/ide-1.6.x-boards-manager/package_damellis_attiny_index.json

Click Ok
Follow this tutorial to install the ATtiny configurations: Programming an ATtiny w/ Arduino 1.6 (or 1.0)

I am using an Arduino Uno to program the ATtiny85, configured as follow

If you are using a programmer to upload the code to the ATitny85, you still need to reset the fuse once.

Load the sketch -> Examples -> ArduinoISP

Compile
Upload into the Arduino Uno

Load the Exemples -> 01.Basics -> Blimk
In the menu tool select

Board: ATtiny
Processor: Attiny85
Clock: 8 Mhz (Internal)
Port: Com port used by the Arduino
Programmer: Arduino As ISP

Fuses

This is the tricky part. It is necessary to reset the clock of the chip.
It is a one time operation.
From the menu Tool, click Burn Bootloader

Now you can upload the code from NeoPixel Code from Adafruit.It should work.

Thursday, September 10, 2015

I2C protocol visualization with Nusbio

I wanted to show you this breadboard experiment, inspired by the Arduino on board led
and also the blogpost Arduino from scratch part 6 – pin 13 led by Rheingoldheavy.com

Video

2 weeks ago I was trying to connect LEDs to each nusbio gpio in parallel to create an on board led feature. And it does not work well and there are side effects, like i2c stop working completely.

So I gave up. But then I heard about the blog post and I just try with an lm358 op-amp and it is working.

Now I am can create my 8 blue on board LEDs PCB. Each LED will light up when the associated gpio is on. It also work when the gpio is open as input in pull up mode.
obviously I will need 8 op-amp.

In the future I will add the 8 blue LEDs and op-amps directly on Nusbio board.
That was one of my idea since day 1.

In this video I plugged an Adafruit i2c 8x8 led matrix into my device Nusbio.
Gpio 0 for the clock and gpio 1 for the data.

I connnected the blue led to gpio 0 via one op-amp and gpio 1 to the red led via the other op-amp (an lm358 is dual op-amp).

I also reduce the speed of the clock to lowest i could which is 1200 baud.

In this video we see the blue and red led flickering. what does it mean?

Well when the blue led is on (the clock) and the red led (the data) is on we are transmetting a 1 from the master to the slave or from the salve to the master and when the red is off we are transmitting a 0.

The red led flickering is the 1 and 0 being sent across the wire. The blue led is the clock, so it just go on/off, on/off is barely visible.

I thought it was cool way to visualized what is going on on an i2c bus, though it is not very precised.

Thanks.