Everything else

The events described in this article take place in July, when I spent some of the best days of my life so far as a summer intern based at Mountain View, CA.

My internship was coming to a close. I wanted to have a namecard to give out to the new connections I made while I was there – and with a little more than two weeks to go then before winding up, I had to make it fast. Having seen a lot of interesting projects that make business/name cards out of printed circuit boards, I decided to do my take on the concept and create a printed circuit namecard for myself. This article describes the thoughts behind the design and what I learned in the process. It was fun nonetheless. Before continuing over to the rest of the article, here’s what the finished card looks like:

The dream phase

“My card would have a small multi-colored LED that would glow whenever someone would hold it in their hands. It would contain my contact information as a QR code and on the back would be whitespace where I can leave someone a handwritten note”.

Which color would it be? The soldermask colors of choice were – OSHPark purple, blue, black and white. Had recently seen a board with a matte black soldermask and liked the feel of it so I was interested in trying it out too.

The card designs I had seen placed all the text on the silkscreen, but maybe putting some part of the text as exposed copper would add more contrast? The effect would look more dramatic when the board gets gold plated (ENIG) vs the usual solder finish (HASL), also the boards would cost more as a result.

The Mock-up

Business card size is 3.5″x2″ ( 89x51mm ). Mine’s 89x50mm to fit a 10cmx5cm bounding box for standard fabrication size.

Mock-up of the card was done in Inkscape. I generated a QR code for myself as a SVG file from here

The QR code is in vCard format, so scanning it reveals my contact details which can be straightaway saved on your phone. Also it was at this point that the fonts and font sizes were frozen. Once it looked good to me, I exported different sections of the file in PNG format, which I would later convert to footprint using KiCAD’s handy utility and position in the board layout as any other component.

The Electronics

For choosing the right microcontroller, there were four requirements – low power, 3 PWM channels, touch sensing and low price. Wanted to use the AVRs initially for ease of use, familiarity (the Arduino framework) but they were roughly around a dollar or more on DigiKey/Mouser. The PICs seemed to fit the bill though in just about half a dollar – selected the PIC12LF1572 microcontroller – that sounded good enough. Also, my first time using a PIC microcontroller – a new platform to learn!

The battery? CR2032s are pretty standard, and also have the highest possible mAh. The next smaller one with a comparable mAh was the CR1632. I decided to go with the CR1632, though next time I might consider a CR1220.

I needed a PIC programmer, found a project on Hackaday.io which meant I could repurpose one of my Arduino boards to do the programming – this project actually gave me faith that I could somehow program the PICs while still being on a tight deadline (thanks to hackaday.io user jaromir.sukuba for maintaining this!) and I decided to give it a shot.

Submitted a Mouser order for all the parts and it all arrived in 3-4 days. The BOM cost was ~$60 for enough to build 40 of these.

The Board Layout

As this was a relatively low complexity design, it was completed in a few hours on an extended night shift.

The key detail here was my name – unlike the other text I put it on the copper layer so that it would get gold plated . To ensure that the soldermask opened up around it, I added a 0.2mm “stroke” around the vector graphic corresponding to my name in Inkscape and put it on the F.Mask layer so that the text is exposed through the mask and would eventually get gold plated. Here you can see what I mean [red = top copper, magenta = top soldermask, green = bottom copper]:

Here’s a shot of the completed layout:

Board Fab

I used Elecrow for this order – they offered matte black soldermask option without a custom quote. I had used them once before and have been satisfied with the quality. One more good thing about them is that they don’t add production codes on the silkscreen of your boards [which can be so annoying on a board design like this] and also send you a picture of the finished board before they dispatch your order [which makes you even more excited to receive the boards once you’ve seen them made as you wanted them to be]. The quality was excellent. From silkscreen to plating and all the vias were properly covered.

I had selected DHL Shenzhen as the shipping method which is supposed to be faster than DHL Hong Kong, the price difference being roughly $5. For a total of 40 boards with matte black soldermask and ENIG finish, paid $100 total. Order was submitted on a Wednesday and the boards were delivered next Wednesday. The boards looked beautiful, just as I had designed them to be 🙂 .

Assembly

There aren’t a lot of components here, this should have been pretty standard stuff but I had lead-free solder paste and that was a big pain to work with a toothpick, without a stencil. I should have probably ordered one along with my boards. And the last week internship rush meant that I couldn’t have enough time – had to choose between doing the firmware or building all 40 on a night stretch – I got a few assembled and that was it.

Firmware

This was the the first time I was using a PIC microcontroller. Moving to a new microcontroller has its own surprises – it took me an hour to realize that the PWM generator won’t update its duty cycle automatically on changing contents in the duty cycle register and a bit has to be set in another register. The MPLAB IDE was mostly okay-ish, although I’d try and see if I can get it working with the SDCC compiler for future firmware revisions.

The MPLAB code configurator provided an easy way to implement the touch sensing functionality here as it had an mTouch library implementation and I was able to get it working just in time. [jaromir]’s PIC programming software worked well and I was able to quickly iterate and build v0.1 .

The chip being a LF series has pretty low standby current but there wasn’t enough time to bake that functionality in. I chose to run the MCU at a lower clock frequency instead (500kHz) to get active currents of the order of 0.3mA. Battery life is two weeks after which the LED dims out.

Here’s a close-up of the finished result. The 5 pins are for programming. A 2mm berg strip is manually held to the headers to program.

Future

I was very satisfied with the finished result. Matte black with a gold finish looks beautiful and to me, was worth it. Also there was excellent service from Elecrow which I would whole-heartedly recommend based on my experience with them. [jaromir]’s PIC programmer allowed me to use one of my Arduino boards to program the PICs, it helped me a lot during this project. Thanks a lot!

With a working v0.1, I was able to build a few and give away. I’ve given away some blank boards too, they look pretty in their own right.

I want to rework the firmware, most likely with SDCC and add some more fade effects on the tri-color LED. And also implement proper low power support (likely by using a WDT to sleep every second and wake up and check for a touch). In the next PCB rev, I would:

• Make the boards 0.8mm thick. Or even 0.6mm.
• Make the QR code larger for better readability and push it to the back side of the PCB – it’s currently all white silkscreen
• Add a little more clearance between the touch sensor pad and the ground plane all around it. It probably decreases the touch sensitivity a bit.
• Use a slot in the board and add a split battery holder leading to a lower Z-height.
• Make a pogo pin set and a 3D printed jig to hold the programming header in place. It’s awkward to hold and press the headers everytime something needs to be flashed.

I’m not posting the board design files yet. However I might post the firmware after adding more effects.

That’s all for this one. If we ever meet in person, ask me to show you and I might even give you one of these.

Here’s an animated GIF:

via GIPHY

The year 2015 saw my project BeagleLogic as a Best Product finalist in the 2015 Hackaday Prize, and my other project Smarter Power Pack  as a semifinalist in the main event. I also got to attend the Google Summer of Code Mentor Summit at Sunnyvale, CA (thanks to BeagleBoard.org) in November 2015 where I met many interesting people and had a great time.

Just the next weekend was Hackaday’s first hardware conference – the Hackaday SuperConference – which would later go on to be a grand success. I however knew that I couldn’t stretch my 8000-mile trip to the weekend because my university end-term examinations began next week and I had to leave on the Thursday before, the 12th of November. I let Sophi (of Hackaday) know and they invited me for lunch with them Thursday afternoon at the Supplyframe office at San Francisco.

Thursday morning, I boarded the Caltrain to San Francisco, and then roughly a 10-minute walk from the station to the office. This is how my entry was announced at the “Hackaday SuperConference” group chat channel at Hackaday.io :

The office at that time was packed and brimming with activity as the entire Hackaday crew had gathered and working together towards the Superconference. I sat on a table beside [Aleksandar Bradic] (CTO, Supplyframe) and [Chris Gammell] (of AmpHour podcasts and Contextual Electronics). Behind me were [Rich] and [Sophi] working on a video-shoot for the Hackaday Omnibus 2015 release (yes, I saw a part of the shoot that day). Here is a link to the released video on Vimeo.

Thanks to [Jasmine], I did not miss the SuperCon badge and T-Shirt. As a proofreader for the Hackaday Omnibus 2015, I received my copy as well.

Now there’s an interesting backstory of the badge here that I think I can share with you: As I put on the lanyard onto the badge, they realized that the drill hole for putting the lanyard on the badges was a tight fit and it would be cumbersome to remove and re-attach the badge without scratching the solder mask on top. The solution? A bunch of keyring rings which would then go on between the badge and the lanyard – like here.

I got to play with the new NVIDIA Jetson TX1 for a while, a test unit of which had just arrived at Hackaday ([Brian] would later publish a hands-on with it, which can be read here). I saw [Brian] and [Mike] typing on what would be the posts that would later go on to the Hackaday blog, and also the HaD tip line, in the short time I was there.

Once [Sophi] and [Rich] were done with a round of shooting for the Omnibus video, we proceeded for lunch to a nearby restaurant. The food was great. The lunch time conversations, even more great.

After lunch we walked back to the Supplyframe office and I bid goodbye to the entire team, and boarded my flight back to India later that night. I had got to see the team behind Hackaday up really close, and my respect for them has only grown since. They are doing a great job with their blog, the Hackaday.io community and the SuperConference which I really missed being a part of this year. A big shout out to them, and also to [Sophi] for making an exception while you all were so busy preparing for the SuperCon so that I could get to be there, and interact with you all. Thanks for having me there! Looking forward to meeting you all again.

Wishing all readers a very Happy New Year 2016 from The Embedded Kitchen.

~Abhishek

An Embedded Kitchen wouldn’t have been complete without the ability to fabricate circuit boards for rapidly prototyping circuits without waiting on the board house [fail fast, fail often applied to hardware design]. This week, it gained the capability to fabricate boards using the well-known toner transfer method.

I had done toner transfer first when I was at school, the results had been terrible. So terrible that I turned to wire-wrap prototyping for my circuits, even when I started using SMD components later. However the realization that dead-bugging SMD parts is too much effort which doesn’t scale brought me back to PCBs. This time because I couldn’t wait for two weeks to get my boards manufactured so I decided to take on toner transfer again. I knew the steps. Clean the board, print the design, iron it on. After the ironing when I rinsed the board under cold water, I was pleasantly surprised to see near-perfect pattern transfer from paper to board. Then I went on to etch them with ferric chloride.

The first boards to be so fabricated are an early stage prototype of my project Smarter Power Pack which uses spare laptop batteries to realize a better power bank (interested? here’s a link for further reading), and a respin of the LCD connector board for my BeagleBone LCD cape. Here are pics of the boards so fabricated:

After this was done, I threw in an additional step of tinning the whole board to protect it from tarnishing and also patch-up any imperfections in traces. Then placing components and reflowing the boards are usual. Here are the results.

They’re not as pretty as the ones got from the board house, but they’re beautiful in their own way. They’re cheaper in terms of money but more expensive in terms of extra effort (drilling and hole plating). And I don’t need to have 5 or 10 copies of tea coasters if I used a wrong footprint or inverted it. But in the end, it’s all worth it when you can get from an idea to prototype in days and not weeks.

I just refurnished The Embedded Kitchen, both on the outside as well on the inside, or I should say, on the front-end and hosting levels; it is still powered by WordPress. I was contemplating moving the site to static pages using Jekyll or Nikola, but WordPress (with Jetpack) now also supports Markdown-based content authoring so the biggest reason for migration to a static system is no longer there so this decision may be deferred indefinitely.

The site is now powered by OpenShift by RedHat PaaS (hover over the word for the definition).

Phase 1 – I just want a Sandbox

I had come across OpenShift some time before and (almost immediately) signed up for the free tier of the service – which gives me 3 “gears” to experiment with whatever I like – PHP, Node.JS, MySQL, MongoDB … . Since I had been contemplating installing a new theme on the website and didn’t want to fiddle with the old site too much so I exported all my data in the WordPress XML format, and created a test site on OpenShift and used it as a sandbox to try out various themes. I settled on Nirvana first (too many choices, I was overwhelmed) and then stumbled across the Freelancer child theme based on the GeneratePress theme framework and liked it more. So that’s the current theme on the website.

After checking my site with PingDom I thought it might be a good idea to migrate the site to OpenShift.

And so wp-embeddedkitchen.rhcloud.com was born.

Phase 2 – blog.theembdeddedkitchen.net

I decided to give the OpenShift version of my blog a proper subdomain blog.theembdeddedkitchen.net (does not exist as of now). This was simple, just one CNAME record to add to my DNS Zone settings, and tell OpenShift and WordPress (admin panel) about it, and boom. Checkpoint 2 crossed.

Now the acid test – getting theeembeddedkitchen.net to point to my blog. I had read enough about CNAME at the root DNS level (since the IP address of RedHat’s service could change without notice, so I cannot just use an A record of the current IP) to be wary of this.

In my excitement, I updated my new blog address in the WordPress admin panel from blog.theembeddedkitchen.net to theembeddedkitchen.net at the point where the DNS hadn’t moved. Yikes! The transition is going to happen faster than it should have.

I added a “Moving” sticky post to the old blog just in case someone might view the site in the transition phase.

Phase 3 – Enter CloudFlare

Of all the alternatives out there, CloudFlare (at least) looked to me the safest. As a side effect, its CDN infrastructure should accelerate my website and help Akismet further in deterring spammers (In over 7 months I guess I had tens and thousands of spam comments)

Configuring CloudFlare was as easy as advertised, just a quick DNS Server change and I was on board CloudFlare. I then added CNAME records and configured OpenShift to catch theembeddedkitchen.net and www.theembeddedkitchen.net for my application. I waited for the DNS changes to take effect and opened theembeddedkitchen.net . All looks well, I think I could call it a day now.

But when I opened www.theembeddedkitchen.net , the site just hung up and I get – “too many redirects”. Wait. A redirect loop! Ok, no problem – I changed my blog URL in WordPress to www.theembeddedkitchen.net and it seems that the problem is fixed. Then I open http://theembeddedkitchen.net and get the same redirect loop. It seemed like a cat-and-mouse game.

However on more digging I figured out that the missing piece of the Jigsaw puzzle to set up a redirect rule on CloudFlare to give a HTTP 301 redirect from http://www.theembeddedkitchen.net/* to http://theembeddedkitchen.net/$1. So if you are stuck in a redirect loop and using both OpenShift and CloudFlare, here’s what you have to do (assuming your-domain.com):

• In the DNS Control panel in CloudFlare settings, add a CNAME for your-domain.com to your destination (theembeddedkitchen.net => wp-embeddedkitchen.rhcloud.com).
  If you do this correctly, CloudFlare will tell you that “CNAME Flattening will be applied to this record”.
• Add CNAME www and point it to your-domain.com (theembeddedkitchen.net)
• Goto the Rules section and set up a redirect rule [HTTP 301] from http://www.your-domain.com/* to http://your-domain.com/$1). This is important to curtail that nasty redirect loop, so that the WordPress installation gets requests only for the non-www domain [Needless to say, the blog address in WordPress should be http://your-domain.com] and CloudFlare takes care of that even before OpenShift kicks in.

All this done the site was back online to its full glory. Now just a few finishing touches…

Phase 4 – Plugins

I installed the Jetpack plugin first so that I could get all the goodies and a site check every 24 hours which ensures that the site never “idles” (apps in the free tier are put into standby if it doesn’t receive an HTTP request in 24 hours).

Also I decided to put a Disqus comment system in place of the old comment form. This was as simple as setting up my Disqus account and installing the Disqus comments plugin.

There’s also WP Super cache that makes this (almost) a static site. Not sure if N levels of caching are going to help anyway but I think it might speed up things a bit.

I am thankful to the shared PHP hosting service provided by edaboard.com to its members which powered my website so far. The old content would still be there, albeit not really accessible for the time being.

And yes, I write this I am finalizing a panel to be sent to the board house. What the circuits are about, is in the next post.
EDIT: Panels are already sent to the board house and I’m waiting for them to arrive. Yay!