#berryclip

It was time to get ready for my first attempt at soldering a PCB. I had only ever soldered some random wires before, and was a bit intimidated at first by the precision required with the PCB. 

The assembly instructions can be found on the Raspberry Pi Spy website. Thankfully, they're quite clear with good links to external sources on soldering. Also, used these instructions as an additional reference.

First, it was time to round up the gear. I had a few soldering irons tucked away, so retrieved them and chose a 15W one for the job. The guides recommended 60/40 solder for electronics, meaning the solder should contain 60% tin (Sn) and 40% lead (Pb). This meant a shopping trip, and found 60/40 solder with 1mm diameter. On the same trip, picked up a soldering iron stand, which also included alligator clips. The clips turned out to be helpful in keeping the PCB in place during soldering. 

Grabbed a few more things before starting: small wire trimmers and a Scotch-Brite cleansing pad for cleaning the excess solder off the soldering iron.

So, time to solder the first joints. Started off with the resistors, as recommended by the guide.

I placed the component and twisted the leads to keep it in place. I then applied the iron to where the lead the solder pad meet, and slowly added some solder. The connection seemed to seal quite nicely, so pulled the solder away, followed by the iron a few seconds later, and repeated the process on the other side. After placing the remaining 330Ω resistors, this was the result. 

I was happy with the result, but in retrospect I'm wondering whether what happened to the PCB coating is normal. Need to look into it. Regardless, I trimmed the leads, and while doing it realized my wire trimmers were basically trash. Made the decision then & there to invest in a decent pair to make future work easier and end results prettier.

Proceeded to place the rest of the components, while saving the connector for last. After soldering them on, I was proud of my minor achievement. LED6 looks a bit funny & crooked, but hey, it gives my BerryClip personality. ;)

The part I was really nerveous about was saved for last. The spacing of the holes with the 26-pin connector is quite narrow, so I was worried about shorting one of the connection. While soldering the pins, I found that the LEDs were intruding a bit and making the work slightly more difficult, but taking it slow the end result turned out just fine. 

The instructions for the BerryClip mentioned using a multi-meter to check for short-circuits. I didn't have a multimeter handy at the time, but what the instructions refer to is a continuity check. Adafruit has a wonderful page explaining continuity and how to use a multimeter, which is worth checking out.

About the soldering iron I used: while the tip was a good size, it's detachable and doesn't have any sort of locking mechanism. The tip came loose a few times during soldering, and I had to push it back in place several times. Did the job, but very annoying, and will be looking for a replacement.

Anyhow, it was time to connect the BerryClip onto the GPIO on the Raspberry Pi and see if my soldering was any good! The webpage for BerryClip had ready-made Python scripts, which made it very easy to test the breakout board. Enter berryclip_09.py, and...

So, I had the Raspberry Pi set up and running Raspbian. Now what?

Going back to my original crazy thought of being able to control a robotic hand from my smartphone for the purpose of squeezing squaky toys, I started abstracting the specific idea to being able to control an external, motorized device from a smartphone. In order to make progress toward that goal, I started breaking down the problem into manageable chunks.

One piece of the puzzle was the communication between a smartphone (in this case a Windows Phone) and the RasPi. Both are WiFi-enabled, so that solves basics. After a bit of searching, I found Brian Dorey's blog, where he describes a central heating control system, implemented with RasPi and Windows Phone. His solution was to use HTTP and run an Apache server on the RasPi, and having previously worked with both, it seems like a nice & simple solution. Since this part seemed straightforward, I decided to defer working on it to focus on areas I'm less familiar with.

Then there's the issue of a connection between the RasPi and an external device. This is where one of RasPi's exciting features, the GPIO (General Purpose Input/Output) connector, comes into play. Like the name suggests, you can plug external devices and move data in and out between them and RasPi through this interface. Thus, learning how to use the GPIO became a priority. Also, using the GPIO brings me to the area I'm most unfamiliar with: building component-level electronic systems, i.e. real hardware hacking.

There are tutorials available about the details of GPIO on Adafruit and a wonderful GPIO cheat sheet on ModMyPi, but I felt I needed a simple, practical project to really get my hands dirty with GPIO and circuitry. Thankfully, through ModMyPi I found the perfect thing to get started with: the BerryClip by Matt Hawkins. The BerryClip is a simple add-on board which plugs into the GPIO connector on the Raspberry Pi, and includes 6 LEDs, a buzzer and a button. The best part: assembly required. The kit ships as components, which need to be first soldered onto a printed circuit board, a PCB. So, the BerryClip would give me something to use through the GPIO, and also require me to get some soldering practice. With a cost of £5.99, I ordered one from ModMyPi.

A few days later, this hit my mailbox. Next post, assembling the BerryClip.