Interfacing two Adafruit MMA8451 via I2C

This week I had to interface two accelerometers (adafruit MMA8451 breakout boards) into one Arduino board.

On Adafruits website, they write that you can address the sensors with 0x1C by adding a pull-down resistor on the “A” pin, or 0x1D by connecting the
“3Vo” to a 3V3 source. What they don’t tell is how to use them both at the same time, which gets clear once you take a look at the Adafruit_MMA8451 class within the library file Adafruit_MMA8451.h.

bool begin(uint8_t addr = MMA8451_DEFAULT_ADDRESS);

metronome

Here you have a simple code based on the library example, but adding the two sensors:

Talk nerdy to me! Where I get my electronics updates and news

Ever wondered where is a good place to find new and interesting chips on the market? Questions about electronics and what is happening in the market?

For the engineers and makers out there, the world of electronics can be a bit overwhelmed with so much happening all the time, updates, news and buyouts (specially in the past few months).

I would to use this post to share some of my favorite places to get new chip information, updates and random electronics questions.

Newsletters

Podcasts

IRC

Do you remember IRC? Yes, it’s still alive and strong. Just connect to the Freenode network and you will find many very interesting channels where you can talk electronics, exchange information and ask questions! If you are there, drop a line to spillere (me!).

  • #electronics on Freenode
  • #avr on Freenode
  • #arduino on Freenode

Forum

Other

  • Fedevel Academy – Learn awesome PCB designing skills
  • /r/nicechips – Reddit, a great place on the internet where people share their findings in the electronic chips market. Really really good!!

This list is still a working in progress. If you have any suggestions please add a comment bellow!

Opening a popup ninja from php

Checking the documentation from popup ninja plugin on how to open the popup from a link, the only available option is how to open from a blog post. But if you want to add the link in your website using php, you need to use the wordpress function do_shortcode. The documentation doesn’t show how to add a do_shortcode with content between the tags.

To open the popup with php, simply get the popup ID and use the code bellow. Just remember to change the text for your desired one.

< ?php echo do_shortcode( '[ninja-popup ID=1234]'.'text to open popup'.'[/ninja-popup]' ); ?>

Checking if php-curl is installed

If you wanna check if php-curl extension is installed in your system, type on terminal

sudo php -m | grep "curl"

If the response from the code above is empty, the extension is not being loaded with php. Then you can install it with:

CentOS

yum install php-curl

Ubuntu

sudo apt-get install php5-curl

Metronome v2.0

metronome

During my first semester of Electrical Engineering back in 2007, I had an introduction to electronics class where by the end of the semester we had to develop an open project. At first I tried to build a AM radio using only passive components, I remember that after hours placing components on the breadboard I managed to make it work, but it was really inconsistent and super noisy. The project was working, but it wasn’t as good as I wanted, so I decided to build something else, something that could be actually useful, that when the metronome idea came alive. Using a few components and a 555 IC I could make the circuit “tick” in a frequency that can be used your music studies.

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