RPi2.IT – Updated Raspbian released for Raspberry Pi – my project continues

Isn’t it a pain when our internet is capped because we have exceeded our download limits for the month?  Anyway, this was our situation for the past week – our 200GB was used up.  Ok, this is about the Raspberry Pi 2.  Remember when I tried it out when it was first released?  The RPi.GPIO module wasn’t working and to get it to work, I had to download and use a non-release version.  Just a few days ago, the Raspbian linux distribution was updated.  As we got uncapped yesterday, I was able to finally download and install it onto a micro SD card.  Raspbian is based on Debian Wheezy and is for Raspberry’s hence the name.  The current kernel is 3.18.

Alright, first thing was to run Python3 and then enter the command  “import RPi.GPIO as GPIO” – success, this was accepted without any errors.  Fantastic, I am now able to “RPi2.IT“.  I went through my standard steps to verify that the hardware was accessible, by downloading wiringPi and pigpio and confirming that these add-ons will access the RPi2 hardware – yes, confirmed that GPIO access was possible.

I checked the i2c bus, and yes, I still need to modify the /etc/modules file to add i2c-dev before the /dev/i2c1 device will show up.  I install i2c-tools then use “sudo i2cdetect -y 1” which ran successfully – showed no i2c addresses visible, because I haven’t connected anything as yet.

Now, this morning, I checked my breadboard wiring.  I have four MCP23017 chips ready to install onto the breadboard.  I applied 12V power to the breadboard, and my led lights up showing that I have power.  Then I used my multimeter to measure the 3.3V power rails.  Why 3.3V, you might ask?  The Raspberry Pi general purpose input output pins are 3.3V pins, so I cannot use 5V without using voltage level converters.

SONY DSC

My previous plan was to use voltage level converters, but have since decided to make everything 3.3V to avoiding the hassle.  I found a nice 3.3V dc to dc converter made by Recom, that takes 6-28V input, and gives me 3.3V out – at efficiencies from 75-88% – not bad.  It has the same pinout as the standard linear voltage regulators like the 78M33 and doesn’t need the input and output capacitors.  In comparison, the efficiency of the 78M33 with 12V input and 3.3V output is something like 27.5% at rated load of 500mA.

Ok, time to bite the bullet – I inserted the four MCP23017 chips, then applied power.  No magic smoke was released – now let out a sigh of relief.  Checking the voltage on one of the interrupt output pins – I get 3.3V, ok – as I will be using these to connect to the Raspberry Pi 2.

SONY DSC

Now, to get on with my software after a long delay waiting for the Raspbian distribution to stabilize for this new model Pi.

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