This AddOhms episode is part 3 of the “design your own Arduino” series. In this one I populate a bare PCB, reflow solder it, debug a few issues, and load the Uno bootloader. Originally, I designed 2 versions of the board. One version contained an error that I planned to fix in the episode. Well, turns out, the “correct” board had two issues which were more interesting.

Check out the #27 show notes for links to a bunch of stuff in the episode, including the design files.

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Five Arduino math fixes for when it is wrong

Check these when your Arduino can’t math

Arduino Math

While the Arduino library does an excellent job of hiding some of C/C++’s warts, at the end of the day, it is still just C/C++. This fact causes a few non-intuitive issues for inexperienced programmers. When it looks like Arduino math is wrong, it is probably one of these reasons.

When people ask me for help with their programming, I check each of these Arduino math mistakes. If your code seems to be hitting a bug, check to make sure it is not how the compiler handles math.

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Arduino EEPROM stores any datatype

.get() and .put() make saving floats easy

Arduino EEPROM Hero 1600px

Funny how a simple idea can spider out into multiple paths. Arduino EEPROM seemed like a straightforward concept. A few a years ago it was as easy as having either 512 or 1024 bytes of flash memory. The Arduino IDE offered an EEPROM library which let you read and write a single byte. Today, however, with many different processor architectures saving data to EEPROM varies. It is now possible to save any datatype to EEPROM but not on all boards and not all using the same method.

While programming an coin accepter sold by Adafruit on an AddOhms live stream, I discovered two “new” methods in the Arduino library. At least, these functions are new to me! A couple of years ago EEPROM.get() and EEPROM.put() appeared. Using these functions, you can store any datatype in EEPROM.

This post covers tidgets related to using Arduino EEPROM to store any value across multiple boards, or platforms. Specifically boards such as the Uno, Nano, Mega, and Zero are covered. Additionally Arduino-compatible boards from Espressif, PRJC, and Adafruit are covered as well.

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Learn Six Oscilloscope Measurements with an Arduino DUT

Grab an Uno and learn how to use your scope!

Oscilloscope Measurements with RTM3004 Alternative

One of the best ways to learn how to use a new piece of test equipment is to use it. Sounds easy, right? The problem is, sometimes when you are in the middle of troubleshooting your circuit, figuring out what the knobs on your scope do is an immense frustration. Use these 6 oscilloscope measurements, and just an Arduino Uno, to learn how to use a new or unfamiliar digital scope.

This tutorial is not a step-by-step guide on how to make each of these measurements on a particular scope. Instead, it is a general explanation on how to setup the Arduino and a screenshot to help identify if you set up your scope correctly. I reference the R&S RTM3004. However, practically any two (or more) digital channel oscilloscope should work.

Between each measurement, I highly recommend using your scope’s default setup (or autoscale) before proceeding to the next one!

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5 LDO Regulator Considerations other than voltage and current

A lesson in reading the data sheet

Pryamiduino R4 with LDO Regulator Disabled

For an AddOhms series, I created a DIY Arduino I am calling the “Pyramiduino.” It is an ATmega328p based board in the shape of a triangle. Other than being cute, the shape does not offer any other benefit. The design features a 3.3 volt LDO Regulator, which is also the subject of this post.

I forgot a fundamental aspect of design: read the freaking datasheet. The board’s LDO regulator was not turning on. Adding a passive scope probe to the circuit suddenly fixed the problem. The regulator turned on. When touching the enable pin, it measured about 1.25 volts.  While I am sure Rohde & Schwarz would like me to ship scope probe with each board, that was not an option. With the impractical fix in place, I got to thinking about that voltage level. I remembered that the datasheet mentioned about 1.2 volts was needed for the “HIGH” threshold. Which meant, 1.25 volts applied to the pin enabled an active low input. Not only that, I remember the datasheet clearly said it had a pull-down resistor built-in. What was going on?

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Pretty often I am asked about how I create the AddOhms animations. Currently, I’m working on the final part of the DIY Arduino Series. In the first part, I showed the elements of an Arduino schematic. The second part showed an overview of the PCB design. Finally, I will take the finished board and explain how to turn it on the for the first time. Lucky for me, there was a “mistake” on the board. This error gives some context for the episode.

I needed to explain how the Arduino Uno’s (and Mega’s) “auto-reset” circuit works. I did a live stream showing how I created the animation sequence for this explanation. Well, I started to explain. After almost three hours of streaming, I was only about half-way through the one-minute explanation.

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While long, I think the stream helps to illustrate the kind of work I put into my videos. Speaking of which, I need to get back to finishing this one.

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Maker Faire 2018, Bald Engineer’s Highlights

Things James saw that were cool

Rabid Transit

The Bay Area’s Maker Faire 2018 encompasses an impressive scope of activities. Pedal-powered live music, fire-breathing machines, kids building stuff, corn dogs, fresh honey, LEDs, soldering, roaming robots, and so much more. The last couple of days I made a few posts on the things I saw at Maker Faire. In this post, I’ll summarize many things that don’t fit together, but I wanted to mention that I enjoyed seeing.

Click here to check out my other Maker Faire 2018 posts. They include first-looks at the two new exciting Arduino boards, five companies I didn’t expect to see at the show, and a photo gallery of my favorite stuff.

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5 Unexpected Brands at Maker Faire 2018

These companies are not who I think of when I think "maker."

Maker Faire, like any festival, is a combination of passion products, startups, and larger companies generating awareness. As I walked around, I noticed many logos and brands. An obvious one to see is Make Magazine. Another I saw that made sense is Digi-Key’s maker.io. They had a strong showing, along with the Arduino booth. But that one is expected since so many projects, not just electronics, have an Arduino in them. That said, there were five brands that I did not expect to see at Maker Faire (and most had something interesting to show.)

(Please note, no mentions came from paid placements. I am genuinely interested in their presence at the show.)

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