Planet Arduino

Making a small number of things with an embedded application is pretty straightforward, you usually simply plug in a programmer or debugger dongle (such as an AVRISP2) into your board with an appropriate adaptor cable, load your code into whatever IDE tool is appropriate for the device and hit the program button. But when you scale up a bit to hundreds or thousands of units, this way of working just won’t cut it. Add in any functional or defect-oriented testing you need, and you’re going to need a custom programming rig.

Adafruit have a fair bit of experience with building embedded boards and dealing with the appropriate testing and programming, and now they’ve updated their AVR Programming library to support the latest devices which have moved to the UPDI (Unified Programming and Debug Interface) programming interface. UPDI is a single-wire bidirectional asynchronous serial interface which enables programming and debugging of embedded applications on slew of the new AVR branded devices from Microchip. An example would be the AVR128DAxx which this scribe has been tinkering with lately because it is cheap, has excellent capacitive touch support, and is available in a prototype-friendly 28-pin SOIC package, making it easy peasy to solder.

The library is intended for use with the Arduino platform, so it should run on a vast array of hardware, without any special requirements, so making a custom programming jig out of hardware lots of us have lying around is not a huge hassle.

Adafruit provide a few application examples in the project GitHub to get you going, such as this ATTiny817 example that wipes the flash memory, sets appropriate fuses and drops in a bootloader.

The UPDI code was taken from the [brandanlane’s] portaprog which is hosted on the TTGO T-Display ESP32 board from Chinese outfit LilyGo, which is also worth checking out.

A little while ago we saw how the AVR Multitool, the AVRGPP learned to speak UPDI, and since we’re on programming interfaces, its possible to get the cheap-as-chips USBasp to speak TPI as well.

As the name implies, the OSEP STEM board is an embedded project board primarily aimed at education. You use jumper wires to connect components and a visual block coding language to make it go.

I have fond memories of kits from companies like Radio Shack that had dozens of parts on a board, with spring terminals to connect them with jumper wires. Advertised with clickbait titles like “200 in 1”, you’d get a book showing how to wire the parts to make a radio, or an alarm, or a light blinker, or whatever.

The STEM Kit 1 is sort of a modern arduino-powered version of these kits. The board hosts a stand-alone Arduino UNO clone (included with the kit) and also has a host of things you might want to hook to it. Things like the speakers and stepper motors have drivers on board so you can easily drive them from the arduino. You get a bunch of jumper wires to make the connections, too. Most things that need to be connected to something permanently (like ground) are prewired on the PCB. The other connections use a single pin. You can see this arrangement with the three rotary pots which have a single pin next to the label (“POT1”, etc.).

I’m a sucker for a sale, so when I saw a local store had OSEPP’s STEM board for about $30, I had to pick one up. The suggested price for these boards is $150, but most of the time I see them listed for about $100. At the deeply discounted price I couldn’t resist checking it out.

So does an embedded many-in-one project kit like this one live up to that legacy? I spent some time with the board. Bottom line, if you can find a deal on the price I think it’s worth it. At full price, perhaps not. Join me after the break as I walk through what the OSEPP has to offer.

What’s Onboard?

There are plenty of input and output devices:

• 7 Push Buttons
• Potentiometers (3 rotary and 1 slide)
• Passive Infrared Sensor (PIR)
• Light Sensor
• Sound Sensor
• LM35 Temperature Sensor
• 10 LEDs (various colors)
• Servo Motor
• Stepper Motor
• DC Motor
• LCD Display
• Buzzer
• Speaker
• RGB LED

In addition, the kit comes with an ultrasonic distance sensor in a little bracket that can connect to the stepper motor. That’s the only part that needs power and ground that isn’t already wired up.

Because the heart of the board is an Arduino UNO clone, you can do anything you like to program it. However, OSEPP touts their visual block diagram language that is basically Scratch. You can use it for free on most platforms and there is even a Web-based version although it can’t download code. It looks like Scratch or other block-oriented systems you’ve seen before.

I’m not usually fond of the visual block languages, but this one at least shows you the actual Arduino code it generates, so that isn’t bad. But you can still use any other method you like such as the standard IDE or PlatformIO.

You can see a video about the board, below.

The Good and the Bad

The board feels substantial and able to withstand a good bit of abuse. There’s a good range of components, and I like that the arduino is a real daughter board and not just built onto the PCB. Despite using the block language, I do like the tutorial booklet. It is very slick and has projects ranging from an IR doorbell to a mini piano. You can see a page below — very colorful and clear.

Of course, the suggested retail price of $150 is a bit offputting. You might think a breadboard with a handful of LEDs and other parts would be a much lower-cost option but just look around for arduino kits for beginners and you’ll find prices are all over the place. On the other hand, with a parts kit you would have to know how to wire up things like stepper motors or DC motors, so there is some value to having it already done for you. There’s also value in not having a bag of parts to misplace.

The jumper wires in the kit have pins on one side and sockets on the other. The pins go into the Arduino’s connector and the sockets go over pins on the components. These aren’t quite as reliable as a spring clip and not as versatile either.

In my mind the worst part of the kit design is that the pins are right next to each of the components. That’s good for understanding, but it makes a mess of wiring. For instance, there are ten LEDs, and connecting them all means stretching jumper wires to both edges of the board The jumpers aren’t very long either, so any complex project is going to have wires crisscrossing the sensors and LCD.

Granted, in this image I could have removed some of the wires from the bundles but that wouldn’t help that much, either. If you need to hook up more than a few of the available components you will have a mess. I would have put some sort of spring clip or even screw terminals and put them all on the top and bottom of the board with clear color-coded marking about where they connect. Then the wiring would all be out of the way. There are probably a few other ways they could have gone, and at this price, they could afford the few extra inches on the PCB.

There are a few other things that would have been nice touches to finish off this kit. I would have enjoyed a short chapter in the booklet about using the Arduino IDE directly so that people know it exists. And having even a small breadboard attached for your own exploration would make sense, but would then call for a different type of jumper wire.

Short Example Using the Distance Sensor

I wanted to do something with the board so I decided to play with the distance sensor and the servo. The distance sensor is a bit annoying both because you have to wire it all up and it has a tendency to fall off when you transport the board.

The demo (you can find it online) won’t win any originality prizes. The program moves the servo to scan from 0 to 180 degrees in 5 degree increments. It measures the distance of what’s in front of it. When it completes a scan, if it saw something close (you could adjust the sensitivity), it moves the sensor back to that position and waits 30 seconds. Otherwise, it keeps scanning.

Really, this is no different from any other Arduino program. That’s kind of the point. Despite the emphasis in the book on the point-and-click language, this is really just an Arduino.

In Summary

For the deep sale price I found, the board will work well for its intended audience of students or anyone starting out with Arduino or microcontrollers. Even a more advanced audience who just wants a way to hammer out a quick prototype might find it worth the $30 or $40 you can sometimes pay. But at full price, it is hard to imagine this makes sense because of the mess of wire routing and limited expansion options.

Machine learning is starting to come online in all kinds of arenas lately, and the trend is likely to continue for the forseeable future. What was once only available for operators of supercomputers has found use among anyone with a reasonably powerful desktop computer. The downsizing isn’t stopping there, though, as Microsoft is pushing development of machine learning for embedded systems now.

The Embedded Learning Library (ELL) is a set of tools for allowing Arduinos, Raspberry Pis, and the like to take advantage of machine learning algorithms despite their small size and reduced capability. Microsoft intended this library to be useful for anyone, and has examples available for things like computer vision, audio keyword recognition, and a small handful of other implementations. The library should be expandable to any application where machine learning would be beneficial for a small embedded system, though, so it’s not limited to these example applications.

There is one small speed bump to running a machine learning algorithm on your Raspberry Pi, though. The high processor load tends to cause small SoCs to overheat. But adding a heatsink and fan is something we’ve certainly seen before. Don’t let your lack of a supercomputer keep you from exploring machine learning if you see a benefit to it, and if you need more power than just one Raspberry Pi you can always build a cluster to get your task done just a little bit faster, too.

Thanks to [Baldpower] for the tip!

How do you tell how much load is on a CPU? On a desktop or laptop, the OS usually has some kind of gadget to display the basics. On a microcontroller, though, you’ll have to roll your own CPU load meter with a few parts, some code, and a voltmeter.

We like [Dave Marples]’s simple approach to quantifying something as complex as CPU load. His technique relies on the fact that most embedded controllers are just looping endlessly waiting for something to do. By strategically placing commands that latch an output on while the CPU is busy and then turn it off again when idle, a PWM signal with a duty cycle proportional to the CPU load is created. A voltage divider then scales the maximum output to 1.0 volt, and a capacitor smooths out the signal so the load is represented by a value between 0 and 1 volt. How you display the load is your own choice; [Dave] just used a voltmeter, but anything from an LED strip to some kind of audio feedback would work too.

Still just looking for a load meter for your desktop? Take your pick: an LED matrix, old-time meters, or even Dekatrons.