World’s Smallest MIDI Synth, Now Even Better

October 28, 2019 by Dan Maloney 6 Comments

We’re pretty sure there’s no internationally recognized arbiter of records like “World’s smallest full-featured polyphonic stereo MIDI synthesizer that fits in a DIN shell”. If there isn’t, there sure should be, and we’re pretty sure [mitxela]’s Flash-Synth would hold that particular record.

This is one of those lessons that some people just can’t leave a challenge alone. First [mitxela] built a MIDI synthesizer into a DIN connector, then a couple of months later he made a somewhat more streamlined version. While both were feats of engineering derring-do, neither was entirely satisfactory. With only square wave synthesis and a limit of eight voices, plus some unpleasant audio issues and a total lack of manufacturability, the next challenge was clear.

We won’t pretend to follow all the audio arcana, of which the video below and the build log have plenty, but the technical achievement is obvious enough. The Flash-Synth has an STM32, a tantalum SMD filter capacitor that dwarfs it, and a few support components on a flexible PCB that folds back on itself twice. This bit of circuit origami is connected to a 5-pin DIN plug and stuffed into the connector’s shell, which in turn mates to a custom-machined metal housing. A stereo audio jack lives at the other end of the assembly, and the whole synth is powered parasitically off the MIDI port.

The first half of the video below is mostly a demo that proves the synth sounds great and can do just about anything; skip to the 22-minute mark for the gory build details. Suffice it to say that [mitxela]’s past experience with ludicrous scale soldering served him well here.

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This Home-Etched ARM Dev Board Is A Work Of Art

October 5, 2019 by Jenny List 26 Comments

One of the step changes in electronic construction at our level over the last ten or fifteen years has been the availability of cheap high-quality printed circuit boards. What used to cost hundreds of dollars is now essentially an impulse buy, allowing the most intricate of devices to be easily worked with. Many of us have put away our etching baths for good, often with a sigh of relief.

We’re pleased that [Riyas] hasn’t though, because they’ve etched an STM32 dev board that if we didn’t know otherwise we’d swear had been produced professionally. It sports a 176-pin variant of an STM32F4 on a single-sided board, seemingly without the annoying extra copper or lack-of-copper that we remember from home etching. We applaud the etching skill that went into it, and we’ll ignore the one or two boards that didn’t go entirely to plan. A coat of green solder mask and some tinning, and it looks for all the world as though it might have emerged from a commercial plant. All the board files are available to download along with firmware samples should you wish to try making one yourself, though we won’t blame you for ordering it from a board house instead.

It’s always nice to see that single board computers are not the sole preserve of manufacturers. If the RC2014 Micro doesn’t isn’t quite your style, there’s always the Blueberry Pi which features a considerably higher penguin quotient.

Tiny LED Cube Packs Six Meters Of Madness

September 8, 2019 by Kerry Scharfglass 11 Comments

When [Freddie] was faced with the challenge of building a sendoff gift for an an LED-loving coworker he hatched a plan. Instead of making a display from existing video wall LED panels he would make a cube. But not just any cube, a miniature desk sized one that wasn’t short of features or performance. We’d be over the moon if someone gifted us with this itty-bitty Qi coil-powered masterpiece of an RGB cube.

Recently we’ve been blessed with a bevy of beautiful, animated RGB cubes but none hit quite this intersection of size and function. The key ingredient here is tiny but affordable RGB LEDs which measure 1 mm on a side. But LEDs this small are dwarfed by the otherwise minuscule “2020” package WS2812’s and APA102s of the world. Pushing his layout capabilities to the max [Freddie] squeezed each package together into a grid with elements separated by less than 1 mm, resulting in a 64 LED panel that is only 16 mm x 16 mm panel (with test points and controller mounted to the back). Each of these four-layer PCBs that makes up the completed cube contains an astonishing 950 mm of tracking, meaning the entire cube has nearly six meters of traces!

How do you power such a small device with no obvious places to locate a connector? By running magnet wire through a corner and down to a Qi coil of course. Not to let the cube itself outshine the power supply [Freddie] managed to deadbug a suitably impressive supply on the back of the coil itself. Notice the grain of rice in the photo to the left! The only downside here is that the processor – which hangs diagonally in the cube on a tiny motherboard – cannot be reprogrammed. Hopefully future versions will run programming lines out as well.

Check out the video of the cube in action after the break, and the linked photo album for much higher resolution macro photos of the build. While you’re there take a moment to admire the layout sample from one of the panels! If this sets the tone, we’re hoping to see more of [Freddie]’s going-away hacks in the future!

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GigaDevice Releasing RISC-V MCUs And Development Boards

August 27, 2019 by Maya Posch 30 Comments

Probably not too many people have heard of Chinese manufacturer GigaDevice who so far has mostly been known as a NOR Flash memory manufacturer. Their GD32 range of MCUs is however STM32-compatible, making them interesting (cheaper) alternatives to sourcing directly from ST. Now GigaDevice has announced during a presentation that they are releasing a range of RISC-V-based MCUs: the GD32V series.

As GigaDevice has not yet updated their English-language website, the information we do have is based on CNX-Software‘s translations from Chinese. The specs for the GD32VF103 series of MCUs are listed by them as follows:

Core – GD32VF103 RISC-V “Bumblebee Core” @ 108 MHz
Memory – 8KB to 32KB SRAM
Storage – 16KB to 128KB flash
Peripherals – USB OTG and CAN 2.0B
I/O – 3.3V, 5V tolerant
Supply Voltage – 2.6 to 3.6V
Package – QFN36, LQFP48, LQFP64, and LQFP100 packages

Whether they are pin-compatible with the GD32 MCUs is still to be confirmed. If that turns out to be the case, then this might be an interesting drop-in solution for some products. From the specs it seems clear that they are targeting the lower-end ARM-based MCUs such as ST’s Cortex-M3-based STM32F103, which are quite common in a large range of embedded systems.

Seeing a performance comparison between both types of MCU would be interesting to see as lower power usage and higher efficiency compared to the ARM cores is being claimed. Both MCUs and development boards are already available for sale at Tmall, with the basic GD32VF103C-START board going for about $11 and the GD32VF103TBU6 MCU (QFN36, 64 kB Flash) for roughly $1.27.

Documentation and SDKs in English seem to be a bit scarce at this point, but hopefully before long we too will be able to use these MCUs without having to take up Chinese language classes.

Thanks to [Flaviu] for the tip!

Blue Pill Makes Cheap But Powerful Morse Tutor

August 7, 2019 by Al Williams 2 Comments

[W8BH] attended a talk by another ham, [W8TEE] that showed a microcontroller sending and receiving Morse code. He decided to build his own, and documented his results in an 8 part tutorial. He’s using the Blue Pill board and the resulting device sends code with paddles, sends canned text, provides an LCD with a rotary knob menu interface, and even has an SD card for data storage.

All the code is on GitHub. If you are interested in Morse code or in learning how to write a pretty substantial application using the Blue Pill and the Arduino IDE (or any other similar processor), this is a great exposition that is also a practical tool.

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Create A Low-Cost, High-Accuracy LCR Meter With An STM32 MCU

July 20, 2019 by Maya Posch 14 Comments

Having a good LCR meter was something which [Adil] had wanted for his personal lab, so as any good university student (and former Hackaday contributor) does, he ended up building his own. Using a Nucleo-F446RE board for the MCU side and a custom PCB for the side that does the actual measuring, he created a meter that reportedly comes pretty close to commercial meters, and for the low price of £55.

Running through some of the theory behind the design as well some design choices, the resulting product is then presented. The choice to not using a standard current shunt, but instead a transimpedance amplifier (TIA) is explained as well. Unfortunately there are no schematics or source code, and the text is somewhat unclear on some points, failing to explain some acronyms that’d make it hard for someone who is not active in this field to understand the full design.

We hope that [Adil] can address those points and provide design files and source code, as it does look like a very interesting project!

Building A Development Board For The STM32 G0 Series

July 16, 2019 by Maya Posch 30 Comments

When [Andy Brown] recently tripped over ST’s new G0 series of MCUs, he figured after some research that the best way to learn everything there’s to know about the STM32G0xx by making his own development board based around the STM32G081. The result is a Nucleo-style board, breaking out all pins to convenient 2.54 mm headers, and with a number of niceties, such as an on-board coin cell and 32.768 kHz LSE oscillator for RTC use and three different power supplies (3.3 V, 2.5 V, and 1.8 V) for the MCU.

The board is programmed with an external ST-Link programmer that connects to the SWD interface on the MCU, with a 20-pin programming header provided. While by no means small or compact, it makes for very easy breadboarding and prototyping, with all 2.54 mm headers accessible from the bottom and top.

As for the STM32G0 series itself, the jury is still out on its performance compared to the F0. The former swaps the Cortex-M0 core for an M0+, with a reduced pipeline length (3 stages in the G0) but increased frequency (64 MHz versus 48 MHz). The G0 has a little bit more SRAM, but so far less Flash storage. According to ARM, this MCU range is designed to remove any need to still use an 8-bit MCU. Big claims, indeed.

The biggest issue which [Andy] had while developing this board was probably with the CH340 USB-UART chip. Ordering them from AliExpress as is common, the CH340G ICs he got just wouldn’t work on the first board revision, forcing him to switch to the CH340E and requiring a board respin. This version has an internal oscillator and as a bonus even came in the original tape packaging when it arrived, instead of in a plastic baggy like with the CH340G parts.

See a video of [Andy] going through the design after the break.

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