A graph from the article, showing dead zones and error bars for the ESP32 ADC

RP2040, ESP32, And An Atmega Have An ADC-Off

March 7, 2024 by 31 Comments

[Simon Monk] got frustrated with bad ADC performance when tinkering with an ESP32 board, and decided to put three of the nowadays-iconic boards to the test – a classic ESP32 devboard, a Pi Pico with an RP2040, and an Arduino Uno R3 with an ATmega328P. To do that, he took a bench PSU, added a filter circuit to it, went through the entire ADC range for each board, took a large number of samples at different points and plotted the results. The plots show us both linearity and precision, as well as ADC dead zones, and the results are quite surprising.

The ESP32 doesn’t only have the most limited ADC with maximum 1V input, it also produces the worst results out of all three, with large error bars and sizeable dead zones at both ends. The Pi Pico, despite being colloquially known for its subpar ADC, produces better results than the ESP32. However, both of them are dwarfed by the ATMega328P’s performance. If you need a dedicated ADC, it might just be a good idea to put an ATMega328P on your board.

The example code is provided, and we are wondering whether there are methodology errors. For instance, the ATMega328P code is written in Arduino-supplied C++, but ESP32 and RP2040 in particular used MicroPython, which does more than just running the code, and MicroPython for ESP32 in particular creates a WiFi access point – something known to induce noise into ADC readings. Nevertheless, this is a fun comparison, and we like when hackers do microcontroller standoffs like that – for instance, check out this review from 2017 which pits a dozen microcontrollers of the time against each other!

A multifactor authentication device showing TOTP codes

An ESP32 MultiFactor TOTP Generator

March 7, 2024 by 20 Comments

MFA, or multifactor authentication, is a standard security feature these days. However, it can be a drag to constantly reach into one’s pocket, scroll to Google Authenticator (other MFA applications are available!), and find the correct TOTP code to log in to a site for a short while. [Allan Oricil] felt this pain point, so they took the problem by the horns and created a desktop MFA TOTP generator to make life just that little bit easier.

TOTP, which stands for Time-based One-Time Password, is a security measure that uses a device or application to provide unique codes that expire after a short time. Two-factor authentication requires a physical item (something you have), such as a key or swipe card, and knowledge of a fact (something you know), like a password, rather than relying on a single factor. This approach ensures a higher level of security. [Allan]’s project is a physical thing one would use with a password or key file.

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Hacking An Actual WiFi Toothbrush With An ESP32-C3

March 5, 2024 by 15 Comments

Following on the heels of a fortunately not real DDoS botnet composed of electric toothbrushes, [Aaron Christophel] got his hands on a sort-of-electric toothbrush which could totally be exploited for this purpose.

Evowera Planck Mini will never gonna give you up, never let you down. (Credit: Aaron Christophel)
Evowera Planck Mini will never gonna give you up, never let you down. (Credit: Aaron Christophel)

The Evowera Planck Mini which he got is the smaller, children-oriented version of the Planck O1 (a more regular electric toothbrush). Both have a 0.96″ color LC display, but the O1 only has Bluetooth and requires a smartphone app. Meanwhile the Mini uses a pressure sensor for the brush along with motion sensors to keep track of the child’s teeth brushing efforts and to provide incentives.

The WiFi feature of the Mini appears to be for both firmware updates as well as to allow parents to monitor the brushing reports of their offspring in the associated smartphone app. With this feature provided by the ESP32-C3 SoC inside the device, the question was how secure it is.

As it turns out not very secure, with [Aaron] covering the exploit in a Twitter thread. As exploits go, it’s pretty straightforward: the toothbrush tries to connect to a default WiFi network (SSID evowera, pass 12345678), tries to acquire new firmware, and flashes this when found without any fuss. [Aaron] made sure to figure out the pin-out on the PCB inside the device as well, opening up new avenues for future  hacking.

We’re great fans of [Aaron] and his efforts to breathe new life into gadgets through firmware hacking. His replacement firmware for the Xiaomi LYWSD03MMC Bluetooth thermometer is one of the best we’ve seen.

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A breadboard showing a tiny ESP32 board and two HMC5883L sensors connected to it on different pins

Avoid I2C Address Conflicts On ESP32 By Pin Muxing

February 28, 2024 by 20 Comments

Using hardware I2C on an ESP32? Do you need to connect multiple I2C devices with the same address? Normally, you wouldn’t be able to do that without extra parts, but on the ESP32, [BastelBaus] has found a nice hack — just connect your devices to different pins and slightly abuse the ESP32 GPIO muxing, no extra hardware required!

Initially, they tried separating SDA and SCL completely, and after a bit of tinkering, that’s worked out wonders! For this method, [BastelBaus] provides example Arduino code you could easily integrate into your project, and shows logic analyzer captures that demonstrate there’s barely any overhead. Later, they’ve also found out that you could multiplex only one of the pins, specifically, SDA, having the SCL line be common! As far as we see, this could also work out with split SCL, but do let us know if that doesn’t sound right.

Typically, such a problem is solved with an I2C multiplexer, and we’ve highlighted projects with them before. However, this simple method could also work on chips like the RP2040 or even the Raspberry Pi 4 — just a bit more limited, since the GPIO muxing for I2C has less available ports! Also, if you’re not using a chip with such a comfortable GPIO mux and you must use devices with overlapping addresses, check out the comment section under our I2C ecosystem article – there’s a fair few other methods you can use. And, if this method ever malfunctions for you, there’s a bunch of very straightforward ways you could debug your bus!

ESP32 Weather Station Looks Great With Color E-Paper Display

February 28, 2024 by 20 Comments

[educ8s.tv] has built weather stations before, but his latest is his best yet. It’s all thanks to its low-power design, enabled by its e-paper display.

The build is based around an ESP32 microcontroller, combined with a BMP180 sensor for measuring barometric pressure, and a DHT22 sensor for measuring temperature and humidity. By taking these values and feeding them into the Zambretti algorithm, it’s possible to generate a rudimentary weather forecast.

The weather station looks particularly impressive thanks to its six-color e-paper display. It’s brightly colored and easy to read, and displays graphs of temperature, pressure, and humidity over time. Plus, by virtue of the fact that it only draws power when updating, it allows the project to last a long time running solely on battery power.

As far as DIY weather stations go, this is an attractive and clean design that offers plenty of useful data to the user. We’ve seen some other neat builds in this vein before, too.

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ESP32 Oscilloscope Skips Screen For The Browser

February 23, 2024 by 29 Comments

An oscilloscope can be an expensive piece of equipment, but not every measurement needs four channels and gigahertz sampling rates. For plenty of home labs, old oscilloscopes with CRTs can be found on the used marketplace for a song that are still more than capable of getting the job done, but even these can be overpowered (not to mention extremely bulky). If you’re looking for something even cheaper, and quite a bit smaller, this ESP32 scope from [BojanJurca] might fit the bill.

The resulting device manages to keep costs extremely low, but not without a trade-off. For this piece of test equipment, sampling is done over the I2C bus on the ESP32, which can manage a little over 700 samples per second with support for two channels. With the ESP32 connected to a wireless network, the data it captures can be viewed from a browser in lieu of an attached screen, which also keeps the size of the device exceptionally small. While it’s not a speed demon, that’s more than fast enough to capture waveforms from plenty of devices or our own circuit prototypes in a form factor that can fit even the smallest spaces.

Of course for work on devices with faster switching times, it’s always good to keep a benchtop oscilloscope around. But as far as we can tell this one is the least expensive, smallest, and most capable we’ve come across that would work for plenty of troubleshooting or testing scenarios in a pinch. We’ve seen others based on slightly more powerful microcontrollers like this one based on the STM32 and this other built around the Wio Terminal with a SAMD51, both of which also include built-in screens.

Reverse-Engineering The ESP32’s WiFi Binary Blob With A Faraday Cage

January 15, 2024 by 36 Comments
The Faraday cage constructed by Jasper Devreker.
The Faraday cage constructed by Jasper Devreker.

As part of a team reverse-engineering the binary blob driver for the ESP32’s WiFi feature at Ghent University, [Jasper Devreker] saw himself faced with the need to better isolate the network packets coming from the ESP32-under-test. This is a tough call in today’s WiFi and 2.4 GHz flooded airwaves. To eliminate all this noise, [Jasper] had to build a Faraday cage, but ideally without racking up a massive invoice and/or relying on second-hand parts scavenged from eBay.

We previously reported on this reverse-engineering project, which has since seen an update. Although progress has been made, filtering out just the packets they were interested in was a big challenge. The solution was a Faraday cage, but on a tight budget.

Rather than relying on exotic power filters, [Jasper] put a battery inside a Faraday cage he constructed out of wood and conductive fabric. To get Ethernet data in and out, a fiber link was used inside a copper tube. Initial testing was done using a Raspberry Pi running usbip and a WiFi dongle.  The Faraday cage provided enough attenuation that the dongle couldn’t pick up any external WiFi signals in listening mode.

The total cost of this build came down to a hair over €291, which makes it feasible for a lot of RF experiments by hobbyists and others. We wish [Jasper] and the rest of the team a lot of luck in figuring out the remaining secrets of Espressif’s binary WiFi blob using this new tool.