Kategorie: Linux

Unfolding the case reveals three solar panels that output 6 V with 3 A (max 21 W) of power. Enough to power a Raspberry Pi Zero or Pico device. We set it up with a Raspberry Pi Zero 2 W in the pocket to test performance. We used a modified version of jbudd’s uptime.sh code to log the uptime (see this Raspberry Pi forum post). Our Zero 2 W was connected to the local Wi-Fi network so we could log in and check the uptime.log file throughout the test. Our first test involved popping a Zero 2 W directly to the USB-A slot in the TX-207 and we hung the charger vertical in a south-facing window. In theory, this sounded good but the TX-207 powered Raspberry Pi Zero 2 W for less than a minute in a whole day. After that, we took it outside and laid it out flat in a garden where it would sporadically power, sometimes for up to six minutes, but our Zero 2 W  would frequently drop out along with the sun. Pairing the TX-207 with a USB battery charger was a game-changer. We coupled it up with a Golf GF-017 2600 mAh battery charger, which held the charge provided by the TX-207 and charged up the battery alongside running Zero 2 W. We started with a completely empty battery charger and our Raspberry Pi Zero 2 W ran up the charge and went for a total of 13 hours and 14 minutes with no downtime.

So, paired with a suitable battery, you can expect a day’s worth of power from this. More than enough to run scripts and handle low-voltage sensor HATs and other hardware.

It’s not listed as waterproof, although it did tip it down one day to no discernible effect. It certainly feels sturdy enough to withstand the elements, as long as you keep an eye on things.

Verdict

8/10

An exciting device to pair with Raspberry Pi Zero 2 W. You’ll need a battery pack for it to work reliably.

Specs

Power: Max power 21 W, Max voltage 6 V, Current 3 A Max, Efficiency >19%

Dimensions: Weight: 0.75 kg Dimensions: 20 (81 unfolded) × 29 × 3 cm

Design: Solar panel – monocrystalline solar cell, Operating temperature +10°C~+40°C, Material PET, Plug type 2 × USB-A (3 A max)

01. LCD character display

This project is based around an LCD display. Our display has 16 characters across two lines and is often referenced as a ‘1602’. These usually contain an HD44780, or equivalent, driver chip that displays the appropriate pixels that make up the characters.

One downside of the display is that the driver chip needs at least six data connections. This uses up GPIO ports, as well as needing lots of wires to the LCD display. A common solution is to have a ‘backpack’ fitted to the rear of the LCD display using a port expander. The example used here is a PCF8574T 8-bit port expander.

02. Designed for 5 V

The port expanders are available on a PCB backpack pre-soldered onto the back of the LCD PCB. This saves you from having to create your own circuit, but it does come with an issue. These circuits are normally designed for 5 V, whereas a Pico uses 3.3 V for the GPIO ports.

Connecting a 5 V signal to a Pico GPIO port could cause permanent damage to the latter, so this tutorial looks at some of the possible solutions to interfacing between devices designed for different voltages.

03. Move pull-up to 3.3 V

If the 5 V device did not have a pull-up resistor, the I2C bus could work with pull-ups to the 3.3 V supply instead. This is shown in Figure 2. The crossed-out resistors are the pull-ups inside the LCD I2C backpack and the two pull-up resistors on the left are connected to the 3.3 V output on a Pico. Unfortunately, this involves de-soldering surface-mount devices, which can be difficult.

04. Unidirectional level shifter

A simple form of level shifter can be used when controlling 5 V devices from a 3.3 V microcontroller or computer. This is often used for controlling NeoPixels from a Pico or a Raspberry Pi. In its simplest form, this is a MOSFET with two resistors (as shown in Figure 3). The gate resistor RG (typically 470 Ω) reduces the in-rush current, and RL is a pull-up resistor (typically 2.2 kΩ to 10k Ω). With no input, the pull-up resistor sets the output high. When a 3.3 V input is provided, the MOSFET turns on pulling the output low. This results in an inverted signal.

The code can be configured to invert the output, or you could add an additional MOSFET to invert it a second time. A two-stage, non-inverting buffer is shown in Figure 4.

05. Bidirectional level shifter

The LCD is controlled from your Pico, so you may expect the signal would only need to go in one direction. However, due to the use of I2C protocol, signals need to pass in both directions. We need a bidirectional level shifter. These can be made using individual MOSFETS, but using a premade level shifter from Adafruit or SparkFun is more convenient. An example is the Adafruit bidirectional level shifter, which has four level shifters on a convenient PCB. This is shown in Figure 5.

The level shifter has just one MOSFET for each channel. This is in an unusual configuration. The circuit can be thought of as two sides, with the left side being for the low voltage and the right for the higher voltage. The MOSFET joins the two together. The schematic diagram is shown in Figure 6.

06. How the level shifter works

If both the low-voltage and high-voltage signals are high, then the MOSFET is off and the signal is high at both sides. If the low-voltage signal (left) drops low, then the MOSFET is in the forward direction and the voltage at the gate will turn the MOSFET on. This will provide a path to ground and so the high-voltage signal (right) will be pulled low. If the high-voltage signal (right) goes low, due to an internal characteristic of the MOSFET a small current is able to flow in the reverse direction. As this happens, the voltage of the source pin dips, causing the MOSFET to turn on. This pulls the voltage down on the low-voltage signal as well.

07. LCD circuit

The level shifter can be inserted onto the breadboard and connected between your Pico and LCD display. Then it’s just a case of adding three buttons for Start, True, and False. These are shown in Figure 1.

The top power rail is used for 3.3 V taken from your Pico’s 3.3 V output, and the bottom power rail is 5 V taken from the VBUS supply from the USB port.

The buttons used are 16 mm push-to-make switches, similar to arcade buttons, but smaller. You can use other push-to-make switches if you prefer.

08. Download the LCD library

The libraries that support the LCD display with backpack are available from GitHub. Upload the files lcd_api.py and pico_i2c_lcd.py to your Pico. You can see a demo using pico_i2c_lcd_test.py. This can be useful for checking your wiring is correct, but you will need to change the pins used for SDA (GPIO 16) and SCL (GPIO 17).

09. Coding the game

The game code (quizgame.py). starts by setting up the three

button

objects, along with

i2c

and

lcd

. It then reads the file quizfile.txt, which contains the questions.

Then it enters a loop which ensures that the game can be played over again.

Within the first few lines of the loop, you can see that it first clears the display, puts a string which starts on the top line, moves to the start of the second line, and then puts another string to that line.

10. Handling button presses

The button presses are handled by having a

while

loop which runs until an appropriate button is pressed. In the case of the Start button, it just looks for that one button, but when waiting for a true and false, it needs to check both the

true_button

and

false_button

to see if either is pressed. It keeps track of the score and then displays the score at the end, pausing for five seconds before restarting the game.

11. The quiz file

The questions are stored in the file quizfile.txt. This has one line per question. Each line should have three entries separated by a semicolon. The first entry is the top line to display, the second is the second line, and the final entry is a letter T or F to indicate whether the correct answer is

True

or

False

.

The file is opened using the

with

statement. Using with means that the file will be automatically closed after the program has finished reading in the entries. The

readlines

method is used to read all the entries into a list.

To separate the text to display from the answers, the

split

method is used. You may notice that it also uses the

strip

method to ignore any whitespaces, such as spaces before the newline character.

The quiz file is created separately and must be uploaded to Pico.

12. Improving the game

The game can be placed in an enclosure to make a complete game. You could start with a standard enclosure and cut holes for the display and buttons, or if you have a 3D printer you can download an example from the Penguin Tutor website. One improvement would be to add some error checking. Without error checking, if there is an invalid entry in the quiz file, the program may crash.

Another possible improvement would be to provide a way to add multiple quizzes rather than just limiting them to a single quiz.

Download the full code.

This kit also has 32 guides from Elecrow with things you can make with the components using the more standard MicroPython language on Pico – and credit to the team, there’s not a huge amount of overlap with the types of projects as well.

Advanced learning

Despite being called an Advanced Kit, it does let you start from the very basics – getting your Pico to blink its own LED. Then other LEDs. Then switches. Before you know it, you’re measuring distances with ultrasonic sensors, creating Catherine Zeta Jones-style laser traps, and even building a robot arm. The difficulty curve for the projects is fairly good, and tutorials will concisely explain how different components work to better your understanding.

At the end of the book you’ll build a robot and program it, but it really doesn’t stop there. With all the different things you’ve made, it’s very easy to get ideas to create new projects or combine other ones to extend their functionality.

Much like this magazine, the guides list the code example and allow you to download it separately in case you need to check it (or just don’t feel like typing it up from scratch).

With the price and number of components, this really is one of the best ways to help a curious maker learn a ton about electronics, Pico, and coding. You could even upgrade a lot of the projects with a full Raspberry Pi. It’s something we’re definitely keeping close to us for future projects, although we may need to make a Toby Sensor using parts from the box to keep it safe.

Verdict

10/10

Packed full of projects at a very reasonable price, this starter kit will follow even an experienced maker around.

Specs

Microcontroller: Raspberry Pi Pico or Pico W

Components: Sensors, jumper cables, robot kit, breadboards, LEDs, inputs, hand tools

Language: MicroPython

Phil set about designing a method of detecting bats that did not fall foul of frequency issues. His several decades of coding experience and, in particular, his expertise in music synthesis, proved ideal when it came to designing a low-cost device based around Raspberry Pi Pico.

Tuning in

The first challenge was working out whether there were any bats around. Bats echolocate using ultrasonic frequencies, well beyond human range, but they can’t be heard and are hard to see: “uniquely for mammals, you need technology to detect and study bats,” says Phil. His approach was to have Pico’s sensors scan all the frequencies and seek out the strongest ultrasonic signal. It took him just three weeks to design a Pico-based bat detector that included an operational amp (one which amplifies weak signals), an ultrasonic microphone, a button, and enough software to detect bats and perform speech synthesis.

However, the working prototype board was “an ugly mess and too fragile to take out on surveys,” says Phil, who then turned it into both a printed circuit board and an ultrasonic recorder, adding the ability to record 384kHz/16-bit WAV files to an SD card. This extended the project’s usefulness and meant he could move on to perfecting the surprisingly challenging ultrasonic recording features. Not one to shy away from a technical challenge, Phil chose 128-bit FFTs (fast Fourier transforms) to ensure even the highest frequency bats could be detected. Pico offers exceptional functionality for its size. “Its rich feature set and programmable GPIOs meant that I needed to add the bare minimum of hardware to the design beyond the Pico,” Phil comments “while offering a combination of low cost, low power consumption and the ability to handle 100% duty cycles when processing 128bit FFTs.” This efficiency means Pipistrelle can be used as a passive recorder for four or five nights, “sleeping during the day, listening during the dark, and triggering recordings whenever bat candidate sounds are heard.” These, he likens to music.

“To hear the bats’ true calls – the bird-like whistles, the peeps, chirps, and high-pitched screams of the Horseshoes – is remarkable.”

Double duty

Two years on from his original prototype, there are now three models: BatWalk, a detector to take on bat walks; PippyG ultrasonic recorder; and Pipistrelle itself, which offers both functions. The recorder can either be used manually for on-demand recording, or set to record overnight whenever a bat call is heard. “Overnight recording lets me shut down more of the Pico to get cleaner recordings,” says Phil, an audio purist keen to banish even the slightest operational sounds of the electronics caused by the need to write to the SD card. Each of these can be bought via his Omenie website, and integrated into your bat detection project. A full bill of materials and instructions are provided.

Though he continues to tinker with the audio, Phil finally feels the project is mature enough for someone to potentially create an Android version of it (since the software is open-source) and sees its further potential for studying other ultrasonic creatures, listing cetacean research, since dolphins use ultrasound, along with small mammals and insects.

“I had designed a few other projects using Raspberry Pi, so I had extra Raspberry Pi’s laying around,” Barry explains. “[I] decided to put my extra Raspberry Pi 3B+ to good use as the +5 V power source [of the] automatic timer for the phone ring killer circuit.”

In the lab

We feel like everyone needs some kind of maker room if they can manage it. Barry though is a professional.

“I have my own electronics lab in my house,” Barry mentions. “Including lots of spare parts, and very sophisticated test equipment, having worked as an independent consultant engineer for many years. That makes building these tiny projects a breeze for me.”

The tiny project involves a little more hardware than software, as it is connected directly into the phone. You can follow along to Figure 1 for the explanation by Barry on how it works.

“The telephone line attaches to the Ring Detector (components C1, D1, D2, D3, R1, and the input to IC1 the optocoupler). Zener diodes D1 and D2, combined with capacitor C1, allow only high-voltage AC signals to reach the input of the optocoupler. Normal voice and dialling tones don’t affect the ring detector at all. The Ring Signal satisfies these high-voltage AC requirements as it is an 80 V RMS (113 V zero to peak) AC signal superimposed on the 47 V DC idle phone line voltage.

“When the phone rings, the input of the optocoupler gets activated. The output of the optocoupler then turns on driving R2 to nearly 5 V DC into the gate of the MOSFET Q1, which momentarily loads down the telephone line with 680 ohm resistor R3 signalling the phone company to shut off the ring signal. This happens so fast that you don’t even hear the phone ring. This describes the operation of the circuit when it is in the ‘Sleep’ mode.”

The Raspberry Pi controls switching sleep mode on or off via powering GPIO pins with a Python program that gets the time from NTP (Network Time Protocol). There’s also a manual toggle in case you’re going to bed early.

Like a baby

“I get a much better night’s sleep just knowing that I will not have my slumber interrupted by another annoying telemarketing call at six in the morning,” Barry tells us.

When we asked about the success of the project, Barry seems not to think there’s much mass appeal for a project like this, as everyone just uses ‘do not disturb’ on their smartphones. While perhaps true, we still think there are plenty of folks who would love to have some manual control over their old landline.

As with the Galactic Unicorn, it comes preloaded with Pimoroni’s own brand of Pico MicroPython firmware and an auto-running demo program that lets you press one of four tactile buttons to choose from four graphical effects: burning flames, eighties supercomputer (random pixels), cycling rainbow, and nostalgia computer prompt.

Again, the Pico W RP2040’s PIO state machines are used – along with 12 FM6047 constant current LED drivers – to control the 3.5 mm pixels at around 300 fps at 14-bit resolution, so there’s no sign of any flicker.

Sounds good

At the rear you’ll find a small 1 W audio speaker along with two Qwiic/STEMMA ports (JST-SH) for connecting breakouts such as sensors. There’s also a battery connector (up to 5.5 V). Positioned at the right-hand edge of the front is a phototransistor to detect light levels. Two metal legs are supplied to use as a stand.

Programming is relatively simple using the PicoGraphics library for shapes, sprites, and a selection of fonts. Check out the full function list in the Cosmic Unicorn MicroPython reference guide. Inspiration can be found in several code examples, including a neat web-server-based paint program for drawing on the display from a computer.

Verdict

9/10

The larger display area opens up more possibilities for projects, such as a weather dashboard, as well as for playing impressive graphical effects and animations.

Specs

Display: 32×32 matrix of RGB LEDs (1024 in total)

Features: Pico W on board, 10 × push-buttons, mono I2S amp and 1W speaker, 2 × Qwiic/STEMMA ports, battery connector, 2 × metal legs

Dimensions: 204 × 204 mm

“I originally saw someone post a flight tracker using an Arduino but it only displayed overhead flights – when there were no planes, it was a blank screen,” Adam explains. “Myniceaccount posted his own project in the comments on Reddit and it included a clock and a flight tracker using Raspberry Pi, so I followed the instructions and built one.

“Afterwards, I kept looking at the empty space and thinking it could be utilised so much more, especially since it was already pulling data from a weather website and flight tracking website. With some help with the coding, more functions were slowly added.” The result is a constantly useful device.

Raspberry Pi in the sky

Rather than use a screen, the project incorporates a 64×32 RGB matrix panel. “I liked the way it looks,” Adam says. “It’s very low key and old school while being easier to read (I think). If you had a screen, you could add more information, but it would become too cluttered. This one is simple and to the point.”

An Adafruit Bonnet controls the panel, which is covered with black tinted acrylic and housed within a case. Once the casing was cut and glued together, Adam set up his Raspberry Pi 3A+ computer and began working on the software.

“Originally the display showed the time, date, and current temperature on the main screen and the flight route, call sign, and aircraft on the other,” Adam continues. “I had the idea to add a weather forecast on the main screen and to add the airline logo, distance, and direction on the flight screen. I just needed help from someone who knew Python to put it all together.

“I found someone, but he didn’t have the setup to test it, so we spent weeks going back and forth – him sending code and me running it, then sending error reports or feedback on what was working and wasn’t working.” After making the time and date smaller, Adam dabbled with a four-day forecast only to realise three-digit temperatures messed up the screen layout. He chopped a day away.

Is it a bird?

Flight tracking remains a very important part of the project. Adam is a keen plane spotter and a device to aid his hobby was his primary motivation. To ensure accuracy, flight information is sourced from FlightRadarAPI.

“When a plane enters a predetermined ‘box’  made from two lat/long points in the config file along with a minimum altitude, it pulls the flight info and lat/long of the plane and compares it to the lat/long of your location,” Adam explains. “As the plane flies through the box, it updates its distance and direction until it’s out of the box, where it switches back to the clock and weather.”

The device now takes pride of place beneath Adam’s TV, allowing him to quickly view its information. “With this device I can hear a plane outside and I can discover what it is,” Adam says. “This project was also my first involving an actual display and casing so it was definitely a new experience for me.”

Subterranean survival

Now throw into the mix inspiration from a book entitled An Immense World: How Animal Senses Reveal the Hidden Realms Around Us (Ed Yong), and Bjørn’s thinking gets even more fascinating. The book explores how animals perceive the world differently from humans, and a specific story about the star-nosed mole resonated with him. The book describes “an intelligent hunter and explorer that navigates its world not through sight, but through touch. This creature, living in darkness, has developed a unique way of ‘seeing’ its environment using its star-shaped snout.” This story illustrated to Bjørn “how different forms of intelligence perceive the world in ways that are almost unimaginable to us.”

Challenge your perceptions

The fallout from all of this was the design and development of Paragraphica, a context-to-image camera that uses data, not light, to create images, and which offers “a different way of seeing the world, one that is based on data and AI interpretation rather than human perception.” Bjørn feels that it’s a tool that falls “somewhere between critical art and consumer product,” allowing users to explore the ‘dreams’ of AI as he sees it, “providing a glimpse into a form of intelligence that is fundamentally different from our own.”

Perhaps the most striking thing about the camera is the design of the cover on the front, where typically on a camera you’d find a lens, and we have the star-nosed mole to thank for that. Nature plays a key part in a lot of Bjørn’s designs, and this small burrowing mammal’s antenna-like snout was “the perfect inspiration for the camera.” In addition, Bjørn wanted the front of the camera to evoke a “data collector”, such as a radio antenna or satellite dish.

Bjørn’s camera works by collecting data related to its location using open APIs, including OpenWeatherMap and Mapbox. This data is used to compose a paragraph (hence the name of the camera) that details a representation of the current place and moment, and this description is then used as the AI image prompt.

“In a way, you can think of this process as filling in the blanks of a template paragraph,” Bjørn suggests. “I then send this paragraph as a prompt for a text-to-image AI model to convert the paragraph into a ‘photo’.” Some of the resulting images have been surprisingly accurate, “but they never look like the real place – it helps to think of the resulting ‘photo’ as a data visualisation.”

Bjørn wrote the software for the project, which uses a mix of a local Python script to simulate key presses, and a web application running in a browser. The web app was made using the Noodl platform, “and essentially gathers key parameters from the web, like weather, date, street name, time, and nearby places, and recomposes them into a template description.”

Dial development

A Raspberry Pi 4 powers the device from within a 3D-printed shell. “Using a [Raspberry] Pi for the project gave me the freedom to prototype fast and explore some ideas for how it would work,” Bjørn explains. “And I also had a Raspberry Pi 4 with a screen already attached to it laying in my workshop, so this felt like a good starting point.”

As with most projects that we showcase, there were challenges to overcome during development, including 3D-modelling and 3D-printing the unique mole-inspired casing, and setting up the code and API pipeline for Raspberry Pi.

Bjørn has also been tweaking the dials on the camera, which enable the user to control the data and AI parameters, thus influencing the final ‘photo’. “I have recently updated the two dials to affect the photo styles and years,” he explains. “Changing the year the photo should be taken at is particularly fun, as you get to picture your street in the 1960s, or 2077 into the future.”

View-finder

Bjørn describes the feedback received thus far as “mixed”, with the area of AI igniting a range of reactions and opinions. Some people saw it as a product, but “struggled to connect it to a problem that needed to be solved.” Others have understood the concept and absolutely loved it.

However, Bjørn feels that it “defiantly shows that the concept and manifestation hit a sensitive point.” He’s clear that his creation was intended to highlight and encourage discussion around AI perception, along with “the increasing use of AI in creative domains and technologies we use daily to capture reality. I think it did the job perfectly.