OTA ESP32 GUI Makes Updates Simple

June 23, 2020 by Al Williams 18 Comments

One of the disadvantages of having cheap WiFi-capable boards like those based on the ESP32 is that you have to update them. If you have even a few in every room of your house, it can be a pain to pull them out and connect them to a cable for programming. Over the air programming is a great answer, and [Kevin] shows how you can control the update via a simple GUI. You can see a video demonstration of how it works below.

[Kevin] uses a ready-made OTA library to do the work, but creates a GUI configuration and downloader tool. There is a manual step to force the board into the OTA mode, which might be a mild inconvenience, but it improves security since you need physical access to the device to do an update.

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ESP32 Becomes Music Player In Under 40 Lines Of Code

June 14, 2020 by Donald Papp 60 Comments

The demo code for [XTronical]’s ESP32-based SD card music player is not even 40 lines long, though it will also require a few economical parts before it all works. Nevertheless, making a microcontroller play MP3s (and other formats) from an SD card is considerably simpler today than it was years ago.

Part of what makes this all work is I2S (Inter-IC Sound), a format for communicating PCM audio data between devices. Besides the ESP32, at the heart of it all is an SD card reader breakout board and the MAX98357A, which can be thought of as a combination I2S decoder and Class D amplifier. The ESP32 reads audio files from the SD card and uses an I2S audio library to send the I2S data stream to the MAX98357A (or two of them for stereo.) From there it is decoded automatically and audio gets pumped though attached speakers.

A few economical components, and only a handful of connections between them.

It’s amazing how much easier audio is to work with when one can take advantage of shuffling audio data around digitally, and the decoder handles multiple formats with an amplifier built in. You can see [XTronical]’s ESP32 player in action in the video embedded below.

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Hackaday Podcast 071: Measuring Micrometers, The Goldilocks Fit, Little Linear Motors, And 8-bit Games On ESP32

June 12, 2020 by Mike Szczys 3 Comments

Hackaday editors Mike Szczys and Elliot Williams fan through a fantastic week of hacking. Most laser cutters try to go bigger, but there’s a minuscule one that shows off a raft of exotic components you’ll want in your bag of tricks. Speaking of tricks, this CNC scroll saw has kinematics the likes of which we’ve never seen before — worth a look just for the dance of polar v. Cartesian elements. We’ve been abusing printf() for decades, but it’s possible to run arbitrary operations just by calling this Turing-complete function. We wrap the week up with odes to low-cost laptops and precision measuring.

Take a look at the links below if you want to follow along, and as always, tell us what you think about this episode in the comments!

Direct download (60 MB or so.)

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Building An ESP32 Smart Power Strip From Scratch

June 10, 2020 by Tom Nardi 33 Comments

Surely the most straightforward way of creating a smart power strip would be to take an existing model and hack in some relays that you could fire with a WiFi-enabled microcontroller. But where’s the fun in that? Instead of repurposing a commercial power strip for his recent project, [Md Raz] decided to just build the whole thing himself.

The project started with a 3D printed enclosure that could hold the electronics and three panel mount sockets. The use of heat-set inserts makes it a bit more robust for future upgrade work, but otherwise it’s a fairly simple rectangular design. Nobody ever said a power strip had to be pretty, right? In addition to the panel mount sockets, there’s also a AC-DC converter to step mains voltage down to 5 VDC for the ESP32.

In addition to the microcontroller, the custom PCB in the power strip holds a trio of MOSFETs connected to AQH2223 solid state relay (SSR) chips. Once the ESP32 toggles the line attached to each MOSFET, the indicator LED above the outlet goes on and the appropriate SSR is thrown to turn on the power. With a simple web interface running on the microcontroller, all three outlets can be independently controlled from any device with a web browser.

If you’d like to limit your interaction with mains voltages, then we’ve seen some projects that commandeer the low-voltage side of a commercial smart power strip. But remember, putting a Raspberry Pi inside of a power strip might seem suspicious to some folks.

A 50W Speaker Made Of Light Bulbs

June 8, 2020 by Jenny List 27 Comments

When we think of a speaker, we are likely to imagine a paper cone with a coil of wire somewhere at the bottom of it suspended in a magnetic field. It’s a hundred-plus-year-old technology that has been nearly perfected. The moving coil is not however the only means of turning an electrical current into a sound. A number of components will make a sound when exposed to audio, including to the surprise of [Eric], the humble incandescent light bulb. He discovered when making an addressable driver for them that he could hear the PWM frequency when they lit up, so he set about harnessing the effect for use as a speaker.

Using an ESP32 board and with a few false starts due to cheap components, he started with MIDI files and ended up with PWM frequencies. It’s an interesting journey into creating multiple PWM channels from an ESP32, and he details some of his problems along the way. The result is the set of singing light bulbs that can be seen in the video below the break, which he freely admits is probably the most awful 50 W speaker that he could have made. That however is not the point of such an experiment, and we applaud him for doing it.

For more MIDI-based tomfoolery, take a look at the PCB Tesla coil.

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Sparklines For Your ESP32 Projects

June 6, 2020 by Jenny List 9 Comments

On a typical microcontroller project we may only have access to a relatively tiny screen. Information display can be a challenge, but it’s one that may be made easier by [0xPIT]’s ESParklines library for Espressif processors using the Arduino framework.

A sparkline is a simple line graph without annotations (like axes or units) intended to fit within the flow of text. They’re largely associated today with the statistician Edward Tufte, and if you’ve not encountered them or Tufte before then we suggest you’ll enjoy educating yourself.

It’s a simple enough library and it comes with example code. Usefully it maintains a data buffer all of its own allowing simple updating, and as well as the examples there is a YouTube video we’ve put below the fold showing graphs evolving as more information is added to them. We’re curious about one thing though, it’s billed as an ESP library, for either the ESP8266 or the ESP32, but we can’t find any ESP-specific code in there and neither could our friendly ESP-guru. Have we missed something? The comments are below if you can shed any light.

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Day Clock Monitors Air Quality Of The Great Indoors

June 4, 2020 by Kristina Panos 6 Comments

As the world settles into this pandemic, some things are still difficult to mentally reckon, such as the day of the week. We featured a printed day clock a few months ago that used a large pointer to provide this basic psyche-grounding information. In the years since then, [Jeff Thieleke] whipped up a feature-rich remix that adds indoor air quality readings and a lot more.

Like [phreakmonkey]’s original day tripper, an ESP32 takes care of figuring out what day it is and moves a 9 g servo accordingly. [Jeff] wanted a little more visual action, so the pointer moves a tad bit every hour. A temperature/humidity sensor and a separate CO₂ sensor output their readings to an LCD screen mounted under the pointer. Since [Jeff] is keeping this across the basement workshop from the bench, the data is also available from a web server running on the ESP32 via XML and JSON, and the day clock can get OTA updates.

Need a little more specificity than just eyeballing a pointer? Here’s a New Times clock that gives slightly more detail.