Remake.IT – Raspberry Pi 3 with 7″ Touch Screen and housing

A while ago, I bought a couple of the new Raspberry Pi 3’s and at the same time, bought a 7″ touch screen and a housing (which was on special) for it from element14.

http://au.element14.com/raspberry-pi/raspberrypi-display/raspberry-pi-7inch-touchscreen/dp/2473872

http://au.element14.com/multicomp/cbrpp-ts-blk-wht/raspberry-pi-touchscreen-enclosure/dp/249469102

As usual, there can be a delay between purchase and actually assembly or use, due to other commitments. Anyway, a couple of nights ago, I decided to assemble the Raspberry Pi with the touchscreen. The touchscreen was pre-assembled, so all that I had to do was to attach the screen cable to the Raspberry Pi 3, then connect the four wires to provide power and the data signals to the touchscreen controller board. By the way, the instructions did not say that the SDA and SCL signals had to be connected and showed only connecting the ground and +5V pins.

I also needed to download the latest Raspbian operating system, and copy the image to a micro-SD card which I did the next day. Then finally plugging in the card, and fastening the Raspberry Pi down with four tiny screens. Next was placing all this in the housing. All went together and I connected up a suitable power supply and powered up.

Voila! Hmm, the display is upside down – ok, and the touchscreen wasn’t working. Checking out the FAQ on the appropriate sites indicates a fix for the display – to rotate by 180 degrees in the /boot/config.txt then a check to see if the touchscreen hardware was seen by the OS.  Yes, the drivers are active so what is going on? I decided that it was time to open it up and check the touchscreen cable.

To my surprise the cable was disconnected and sticking up at a right angle – then the penny dropped. Putting the case on, must have disconnected the cable, which was connected, but now is not.

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This is the touchscreen cable, the one that is attached to that black square chip – the cable is a little bent at the edge which meant that something was pressing on it. Turning the back of the case around showed me the problem.

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The cutout for the touchscreen cable has a sharp edge, which was pressing down on the edge of the touchscreen assembly with the chip on it, and since the thinner cable is not that long, pushing down on it would pull that thin cable out. Which is what must have happened. I measured the distance from the edge of the case to that touchscreen assembly, then marked on the case where I needed to remove that sharp edge. I got out my trusty file which happened to be almost the right width at the area I needed to file out, and proceeded to remove some plastic material making that marked area more rounded which would reduce the pressure on that assembly.

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Here is the final result. After careful reassembly and checking of the cable which was can just see through slots in the casing for the HDMI socket, I can confirm that the touchscreen cable is still attached.

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After powering up, I now have touch!

 

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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.

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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.

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