Kategorie: Linux

See also: Enviro + review

The Enviro (£28/$30. Pimoroni)also features the same slimline pHAT form factor to match the size of a Raspberry Pi Zero, although it can be used with any Raspberry Pi model.

Sensing the world

The Enviro’s BME280 weather sensor monitors temperature, barometric pressure, and humidity. As on the Enviro +, this has been positioned at the left edge of the board, away from Raspberry Pi’s CPU, and there’s even a little smile-shaped slot around it to help reduce heat radiated through the board. Even so, you’ll need to adjust its temperature reading for accuracy (by measuring that of the CPU itself and deducting a factor of it).

A smartphone-style LTR-559 light and proximity sensor detects the ambient light level and also proves handy as a substitute for a push-button when you put your finger on it. The board’s tiny MEMs microphone measures sound levels, useful for monitoring noise pollution, and can also be used to record audio.

At the time of writing, most of the code examples provided with the Python library are aimed at the Enviro + Air Quality board. However, it’s easy to edit the code for missing sensors from the all-in-one example to get it showing rolling graphs for temperature, pressure, humidity, and light level on the LCD. There are also a couple of examples that make use of the mic to plot noise levels and frequencies.

If you don’t need to test air quality and just want a simple environmental sensor with a built-in display, the Enviro is ideal. The light sensor could also come in handy for use in IoT setups, such as to trigger your lights to come on when the light level falls below a certain level.

If you also require motion/direction sensing, the original Enviro pHAT is still available (albeit without the mini LCD).

Specs

• Built-in sensors: BME280 temperature/pressure/humidity, LTR559 light/proximity, SPH0645LM4H-B noise

• Display: 0.96-inch colour LCD (160×80)

• Dimensions: 65×30×8.5 mm

Verdict

Lacks the gas sensor of the Enviro + Air Quality board, but features the same mini LCD screen to display your environmental data without a monitor.

8/10

Raphaël tell us that he increasingly found components for first-generation digital pipe organs – many of which are installed in churches across the world – to be either obsolete, expensive, or simply unobtainable, threatening to consign many an instrument to the scrap-heap.

The solution has been Organnery, a project to to strip the organs of their old electronics and replace them with something new. “After some thoughts and calculations, we came up with a method that would retain the console, keyboard, and controls and instead make use of a small, affordable, and efficient single-board computer,” he says.

The chosen device was a Raspberry Pi, selected because of its worldwide availability, strong development community, and affordable price. It offered a perfect way of bringing pipe organs back to life so that they can be played as before, while allowing modern options such as a touchscreen.

“There are lots of good HATs available covering sound output, MIDI, and control interfaces,” says Daniel James, boss of 64 Studio, the company tasked with creating the software.

Fine tuning the Organnery

As such, Daniel and colleague Chris Obbard began to work on a customised Debian GNU/Linux image called Organnery (GitHub link) that made use of the open-source classical organ modelling software Aeolus and Raspberry Pi’s capabilities. With eleven different temperaments, variable tuning, three or more manuals, and a pedal board, as well as MIDI in/out control and the flexibility to play different sounds, a personalised experience is possible.

“Organnery needed to be set up as a single-use appliance, and the requirements came directly from the organists we’ve been working with to refine the system,” Daniel says. “We made adjustments to the Aeolus source code as well as to supporting programs. These included Mididings, a scriptable MIDI router and processor written in Python.”

Daniel also created minimal system images based on Debian Buster using Dibby, which is a collection of scripts that leverage the distro’s packaging tools. “This approach was a far leaner and more reproducible way to build appliances than starting from a standard image and stripping the system down,” Daniel says.

Retro hits

So what’s the verdict? “Organnery offers a major sound upgrade since the sound produced by the Aeolus software is of a much better quality than digital electronics from the 1980s,” Raphaël says. “It gives the organ player access to new ‘pipes’ and complete control over sound placement in space, from a standard stereo system up to 3D Ambisonic diffusion.”

Most Organnery systems are being retro-fitted into existing organs, but the system can be built from scratch using standard and affordable MIDI hardware. “Some of the smaller organs made for the domestic market have a five-pin MIDI Out socket and can be obtained for next to nothing,” Daniel explains. “Aeolus and Organnery can also make learning the classical organ much more accessible than it has been in the past.”

Even so, bringing organs back to life, complete with the original woodwork and physical controls, is perhaps most satisfying. “Church organ consoles are also often made of expensive hardwoods so we are saving trees,” Daniel says. For organists used to the age-old interface of their instruments, that’s sure to be extra music to their ears.

“For me, the goal has been to encourage a new generation of bedroom coders,” says legendary games developer Jim Bagley, who is among a group of Spectrum fans behind the project. Jim has been programming games professionally for the past 31 years and is a key member of the specnext.com team dedicated to bringing back the ZX Spectrum.

With 3113 Kickstarter backers handing over £723,390 in cash, many others potentially share that dream.

Work has certainly progressed well. “When the Next was first announced three years ago, it was intended to be a normal Spectrum with an SD card and a Raspberry Pi Zero as an extender,” Jim explains. “Raspberry Pi was going to be used to add extra features such as hardware sprites and hardware scrolling so that newcomers would find it easier to code the computer and get the wow factor of getting something running instantly on the screen.”

During the Kickstarter campaign, however, a large field-programmable gate array (FPGA) was announced for the Next – a configurable integrated circuit which allowed the hardware sprites, scrolling, and other advanced features to be incorporated within the machine itself. “It freed up Raspberry Pi Zero to do something else,” Jim says. So the developers began to play around.

Load and run

One of the initial ideas was to recreate the feel of loading a game from tape – generating the series of scratchy, beepy, high-pitched noises which could be heard as a program was ingested into the computer. On the original hardware, this was accompanied by a loading image slowly building on the screen and animated stripy borders.

Rather than have Next users connect a cassette deck, the developers had a cunning plan. “We thought it would be a good idea to have commands sent back and forth between the Next and Raspberry Pi Zero,” Jim says. This developed into a tool allowing a TZX file (a format that stores an exact copy of a ZX Spectrum tape) to be uploaded from an SD card to Raspberry Pi Zero. By sending it back down to the new-gen Speccy through an audio-in pin, the Next would be fooled into thinking it’s loading a cassette. “It gives the original feeling of loading from tape,” Jim affirms.

Are you there, SID?

Having a Raspberry Pi Zero accompanying the Next has also enabled other audio delights. A Sound Interface Device (SID) emulator has been developed that allows audio created for Commodore’s SID programmable sound generator chip to be played on the Next.

It will also be possible to enjoy Atari ST audio files and tunes created using music trackers on the Commodore Amiga. “We can send the audio through a GPIO pin and it goes straight to the FPGA, where it’s mixed with the audio of the Next,” Jim explains. To achieve all of this, the developers have used DietPi to create a new OS called NextPi. “It remains a fully functioning Raspberry Pi Zero that is running at the same time as the Next, but we wanted the Next to be more in control.”

The most recent extra use for the Next’s Raspberry Pi Zero is the ability to connect the latter to its own display. “It’s possible to send screens to Raspberry Pi Zero so that you can have a dual screen,” Jim says. “This means you could have a game being played on the Next, with a global map or stats shown via Raspberry Pi Zero.”

The team is now looking to get USB controllers to work via Raspberry Pi Zero, allowing them to be read by the Next. “We’d also like Raspberry Pi Zero to help with 3D maths so you can take vertices, have them rotated, and passed back,” Jim says. In the meantime, the team is readying the new computer for a January release and a new Kickstarter is being planned for those who didn’t pledge the first time around. We’re certainly looking forward to seeing where it – and RaspberryPi – goes next.

Raspberry Pi loading

1. Games in the file format TZX – a tape format used for preservation purposes – need to be saved on to an SD card and inserted into the ZX Spectrum Next. 

2. A game can then be selected via the Next computer’s built-in Browser mode. Raspberry Pi Zero will be instructed to load the game’s data from the SD card.

3. Raspberry Pi Zero sends the data back to the ZX Spectrum Next as audio and this generates the once-familiar loading noise and loading screen ahead of the game running.

Looking for some more retro gaming joy? You could always: code your own retro games console, build your own retro game with PICO-8, indulge in an entire issue of The MagPi dedicated to retro gaming or this incredible hardback ‚Code The Classics‘ guide, brand-new from Raspberry Pi Press for a more £12?

A lot of projects need specific tools, and there’s a lot out there to choose from. Raspberry Pi maker Mark Vanstone takes a look at the 50 best physical and digital tools you can use to build projects.

Click here to buy The MagPi magazine issue #89

Raspberry Pi kit & gadget guide

Quickly do more with your Raspberry Pi with kits and accessories. Our guide to the best add-ons, HATs, starter kits, robot builds and accessories has everything you need.

Add internet to a classic computer

Missing the days of dial-up? Build an interface to the modern world for an old computer (an Atari ST, in our case) using a RS232 receiver.

Design a 3D printer pendant with BlocksCAD

BlocksCAD is a 3D model editor that runs just fine on the faster Raspberry Pi 4. In this tutorial we look at how to use this Scratch-like language to design a pendant for a 3D printer.

Aquatic Mini Observation System

We’ve got the best community projects every month. Murray Lowery-Simpson used Raspberry Pi at the heart of this solar-powered, autonomous boat that measures water quality.

Cheeseborg

What could be more entertaining than this AI-powered grilled-cheese sandwich machine? We take an in-depth look at this capable cheese-making robot.

Plus! Win one of five Raspberry Pi and black Official Case kits.

The MagPi is available as a free digital download, or you can purchase a print edition online or in stores.

Save 37% off the cover price with a subscription to The MagPi magazine. Try three issues for just £5, then pay £25 every six issues. You’ll save money and get a regular supply of in-depth reviews, features, guides and other PC enthusiast goodness delivered directly to your door every month.

Subscribe

Save 37% off the cover price with a subscription to The MagPi magazine. Try three issues for just £5, then pay £25 every six issues. You’ll save money and get a regular supply of in-depth reviews, features, guides and other PC enthusiast goodness delivered directly to your door every month.

Subscribe

VR to RL

Minecraft can be hacked with a bit of code so that you can make it do as you wish. But this also means that, via more code, it can interact with reality. David Stevens made it so changes to the Christmas tree in the game alter the lights outside. Clever!

Advanced tree lights

We quite like the smart lights we made ourselves, but if you want to do some serious Christmas tree hacking, we suggest taking a look at this amazing project on Instructables.

Upgrade your office

If you find fishing names out of a hat a bit old-fashioned, you can always have Babbage Bear choose for you. Squeeze his hand and he’ll print out a piece of paper showing who you need to buy for. There’s a £5 gift limit, though.

Home light automation

This is a serious amount of lights all over this house to be controlled by a Raspberry Pi. David does so using a phone to connect to Raspbian via VNC.

Raspberry Pi fireplace

Some people like to turn on the fireplace video on Netflix; others prefer to create digital fires of their own. This one also does the impossible and can cycle through different colours of flame.

Make a list

A modern take on the palm readers you used to find on seaside piers, although this machine takes a more binary approach: are you naughty… or nice? Think happy thoughts.

Drop the house bass

Another project where a house has been kitted out with full Raspberry Pi-powered lights – only this one plays music and syncs to it as well. Especially phat dubstep tracks.

Catch Saint Nick

This is a fun Scratch project that allows you to go to sleep happy in the knowledge that you won’t miss Santa. Maybe you’ll find out exactly how big his sack of toys is.

Hack the magazine

A couple years ago we made a little project that allowed you to turn a copy of The MagPi into a light-up Christmas card. Grab the PDF, print the cover on card, and give it a go!

Send us your holiday projects

Made something with Raspberry Pi for this holiday season? Send us photos on Twitter (@TheMagPi) or via email and we might feature you in the next issue!

When you get your starter set, you have to prepare the cardboard base by pushing out hexagons to leave holes to mount the tiles in. Do not discard these hexagons, because we are going to use them in our project. If you have already discarded them, then you’ll need to cut out a hexagon from either cardboard of the same thickness or 3 mm plywood. We made two types of sensor: a standalone one, and ones where you have to modify an existing part. Just like the GraviTrax system, our approach is modular and you can make as many of each sensor type as you like.

How does this Gravitrax hack work?

All the sensors in this part use light to detect the presence of a ball – through breaking a beam, detecting reflected light, or simply the presence or absence of ambient light. As such, the circuits are all very similar as shown in Figure 1; the only difference is the physical sensor used, and the current limiting resistor value on the LED. They are connected to the Raspberry Pi by a length of three-wires-wide ribbon cable, with a pull-up resistor going on the board that connects to the GPIO pins. In later parts of this tutorial series, we will look at making a distribution board for them all.

Optical slot sensor

The first sensor we will look at is an optical slot sensor. This fits under a track and the height can be adjusted by using the small or large height tiles. Basically, this is a cardboard hexagon with a small piece of 3 mm plywood stuck on it and the electronics glued to that, going from point to opposite point on the hexagon. The physical construction of the electronics board is shown in Figure 2, with the whole assembly shown in Figure 3. It is best to glue the electronics in place with a track running through it, between two pieces, so you can get it aligned precisely.

Reflective detector

The previous sensor needs to be placed under a track, whereas this one can be placed in an adjacent space and it looks downwards. It is capable of detecting balls on the entrance or exit to any of the tiles, be it basic, curved, or launch pad. The sensor is easy to make, as the LED and transistor symbols are drawn on the part. We used a stack of five cardboard hexagons glued together, followed by a plywood hexagon with a hole in the centre and a 10 mm, M3 countersunk screw sticking through it. This was then placed on the arm, and could be rotated to the required point.

Making the reflective detector

Figure 4 shows the measurements of the plywood arm, and the mounting bracket made from a piece of 12×12 mm angle aluminium. The arm should be notched with the corner of a square file; this is so a cable tie can grip the ribbon cable without slipping. The height of the sensor is adjustable due to a long slot in it, allowing it to be slid up and down. You need a gap of about 2 mm between the sensor and the top of a ball to detect it reliably (Figure 5). You can mount two arms on a stack to get coverage of another position.

A track monitor

The last two sensors have been standalone; the next one modifies a GraviTrax part. The physical layout is shown in Figure 6. The TCRT1010 sensor comes with bent leads which neatly wrap round two holes of stripboard. On the strip side, you need to bend the connectors over again and cut them short. Then bend the middle two so they sit on one track and solder them up. You also need a surface-mount 51Ω resistor to make it small, although a 025 W through-hole resistor could be used. The assembly needs hot-melt gluing onto the track (Figure 7).

Launch pad monitor

Take an OPB706B sensor and wrap it round the centre post in the launch pad tile (Figure 8). Push it down and use a pencil to mark the outline on the wall. Then, using a Dremel, and 1 mm router bit, cut to about 1 mm short of the outline you drew, so the part does not go through the hole. Also, cut a slot in the opposite side to let the wires through when attached to a height tile. Paint black the area the sensor is pointing at, and glue a 10×2 mm piece of 1 mm thick styrene to the green plunger with polystyrene glue (Figure 9).

Switch monitor

This uses ambient light to detect which way the switch is set. Draw in pencil around the switching lever in both positions, showing the area being covered and uncovered. Then drill a 2 mm hole in the middle of this area (Figure 10). Next, paint the underside of the switch tile black, and make sure you paint on the inside of the hole (Figure 11). The schematic of this sensor is somewhat different from the others and is shown in Figure 12. Finally, Figure 13 shows the physical layout of the parts. Position the board so you can see the white sensor through the hole and fix with Sugru.

Software to control the hacked GraviTrax

We have written software, shown in the sound_trigger.py listing, that monitors these sensors, and triggers sounds, either immediately or after a delay.

Click here to visit the Pi Bakery GitHub page and download the code.

The software is modular: line 82 determines what GPIO pins you will use and it automatically generates a window size to accommodate the number of pins in this list. Note if you want to use GPIO 14, you should disable SPI before booting with the sensor attached. The sounds’ names are in a list at line 88; by simply changing or adding to this list, different sounds can be used. The GPIO pins are scanned and when a trigger condition is met, the event is put in a pending list to be actioned at the correct time.

Using the software

The user interface is shown in Figure 14. For each line, you can set what the trigger action will be. These states are: disabled, when the signal goes high, when it goes low, or when it goes either high or low. They are changed by clicking on the trigger icon. The delay column, as you might expect, determines a delay between the trigger and the sound, whereas the sound sample played can be changed by the icons on the right. You can change the GPIO pin and note that one pin can trigger different actions; so, for example, you could have the switch tile generating a different sound depending if it is changed to the left or right.

Choosing sounds

We found short sounds were generally best, but longer sounds can be useful at the beginning or end of your run. We copied a lot of sounds from the Scratch media library from the path /usr/share/scratch/Media/Sounds into our sounds directory. Make sure that are all .wav files, because that suffix gets added automatically to the file names. Note that the slot sensor will read as a logic zero with no ball, whereas a reflective sensor will read high in the absence of a ball. There are lots of suitable sounds available online as well.

We have looked at adding optical sensors to detect where a ball is, be it on a track or a tile. Next month we will look at how to add different sorts of LED displays to enhance your GraviTrax layout. In the meantime, if GraviTrax is new to you, then have a play with the different layouts in the accompanying booklet.

Tip! Track monitor

When gluing the PCB to the track, glue the long edge first, then push the sensor slightly so it is not parallel to the track, and test that it detects the ball before gluing the sides to hold it into position.