Posts | Comments

Planet Arduino

Archive for the ‘i2c’ Category

You’d be hard pressed to find an IT back office that doesn’t have a few Cisco routers or switches laying around and collecting dust. We’d even bet there are a decent number of people reading this post right now that have a stack of them within arm’s reach. They’re the kind of thing most of us have no practical application for, but we still can’t bear to throw away. But it looks like [Sven Tantau] has found an ideal middle ground: rather than junk his Cisco Catalyst switches, he turned them into automatic bartenders.

Inspired by all those perfect little square openings on the front, [Sven] loaded each switch with a whopping 24 peristaltic pumps, one for each Ethernet port. To fit all his plumbing inside, the switches were naturally gutted to the point of being hollow shells of their former selves, although he does mention that their original power supplies proved useful for keeping two dozen power-hungry motors well fed.

The motors are connected to banks of relays, which in turn are thrown by an ESP32 and an Arduino Nano. [Sven] explains that he wasn’t sure if the ESP32 could fire off the relays with its 3 V output, so he decided to just use an Arduino which he already knew could handle the task. The two microcontrollers work in conjunction, with a web interface on the ESP32 ultimately sending I2C commands to the Arduino when it’s time to get the pumps spinning.

[Sven] mentions his robotic bartenders were a hit at the 2019 Chaos Communication Camp, where we know for a fact the computer-controlled alcohol was flowing freely. Of course, if you don’t intend on carrying your barbot around to hacker camps, you can afford to make it look a bit swankier.

A Raspberry Pi Zero (W) and Arduino are very different animals, the prior has processing power and connectivity while the latter has some analog to digital converters (ADCs) and nearly real-time reactions. You can connect them to one another with a USB cable and for many projects that will happily wed the two. Beyond that, we can interface this odd couple entirely through serial, SPI, I2C, and logic-level signaling. How? Through a device by [cburgess] that is being called an Arduino shield that supports a Pi0 (W). Maybe it is a cape which interfaces with Arduino. The distinction may be moot since each board has a familiar footprint and both of them are found here.

Depending on how they are set up and programmed, one can take control over the other, or they could happily do their own thing and just exchange a little information. This board is like a marriage counselor between a Raspberry Pi and an Arduino. It provides the level-shifting so they don’t blow each other up and libraries so they can speak nicely to one another. If you want to dig a bit deeper into this one, design files and code examples are on available.

Perhaps we’ll report on this board at the heart of a pinball machine retrofit, a vintage vending machine restoration, or maybe a working prop replica from the retro bar in Back to the Future II.

A Raspberry Pi Zero (W) and Arduino are very different animals, the prior has processing power and connectivity while the latter has some analog to digital converters (ADCs) and nearly real-time reactions. You can connect them to one another with a USB cable and for many projects that will happily wed the two. Beyond that, we can interface this odd couple entirely through serial, SPI, I2C, and logic-level signaling. How? Through a device by [cburgess] that is being called an Arduino shield that supports a Pi0 (W). Maybe it is a cape which interfaces with Arduino. The distinction may be moot since each board has a familiar footprint and both of them are found here.

Depending on how they are set up and programmed, one can take control over the other, or they could happily do their own thing and just exchange a little information. This board is like a marriage counselor between a Raspberry Pi and an Arduino. It provides the level-shifting so they don’t blow each other up and libraries so they can speak nicely to one another. If you want to dig a bit deeper into this one, design files and code examples are on available.

Perhaps we’ll report on this board at the heart of a pinball machine retrofit, a vintage vending machine restoration, or maybe a working prop replica from the retro bar in Back to the Future II.

In the era of touch screens and capacitive buttons, we’d be lying if we said we didn’t have the occasional pang of nostalgia for the good old days when interfacing with devices had a bit more heft to it. The physical clunk and snap of switches never seems to get old, and while you can always pick up a mechanical keyboard for your computer if you want to hear that beautiful staccato sound while firing off your angry Tweets, there’s a definite dearth of mechanical interface devices otherwise.

[Jeremy Cook] decided to take matters into his own hands (literally and figuratively) by designing his own multipurpose USB rotary input device. It’s not a replacement for the mouse or keyboard, but a third pillar of the desktop which offers a unique way of controlling software. It’s naturally suited to controlling things like volume or any other variable which would benefit from some fine tuning, but as demonstrated in the video after the break even has some gaming applications. No doubt the good readers of Hackaday could think of even more potential applications for a gadget like this.

The device is built around the diminutive Arduino-compatible PICO board by MellBell, which features a ATmega32u4 and native USB. This allowed him to very rapidly spin up a USB Human Interface Device (HID) with minimal headaches, all he had to do was hang his buttons and rotary encoder on the PICO’s digital pins. To that end, he [Jeremy] used the fantastic I2C rotary encoder designed by [fattore.saimon], which readers may remember as a finalist in the Open Hardware Design Challenge phase of the 2018 Hackaday Prize. He also added a NeoPixel ring around the encoder to use for some visual feedback and because, well, it just looks cool.

Since all of the core components are digital, there’s not a whole lot required in the way of wiring or passive components. This let [Jeremy] put the whole thing together on a piece of perfboard, freeing him up to spend time designing the 3D printed enclosure complete with translucent lid so he can see the NeoPixel blinkenlights. He got the tolerances tight enough that the whole device can be neatly press-fit together, and even thought to add holes in the bottom of the case so he could push the perfboard back out if he needed to down the line.

[Jeremy] spends a good chunk of the video going over the software setup and development of the firmware, and details some of the nuances he had to wrap his head around when working with the I2C encoder. He also explains the math involved in getting his encoder to emulate a mouse cursor moving in a circle, which he thinks could be useful when emulating games that originally used an encoder such as Tempest or Pong.

We’ve seen similar USB “knobs” in the past for controlling volume, but the additional inputs that [Jeremy] built into his version definitely makes it a bit more practical. Of course we’re suckers for interesting USB input devices to begin with.

Amazon might not be happy about it, but at least part of the success of their Fire TV Stick was due to the large hacking and modification scene that cropped up around the Android-powered device. A quick search on YouTube for “Fire Stick Hack” will bring up a seemingly endless array of videos, some with millions of views, which will show viewers how to install unofficial software on the little media dongle. Now it looks like their latest media device, the Fire TV Cube, is starting to attract the same kind of attention.

The team at [Exploitee.rs] has recently taken the wraps off their research which shows the new Fire TV Cube can be rooted with nothing more than an Arduino and an HDMI cable you’re willing to cut apart. Of course, it’s a bit more complicated than just that, but between the video they’ve provided and their WiKi, it looks like all the information is out there for anyone who wants to crack open their own Cube. Just don’t be surprised if it puts you on the Amazon Naughty List.

The process starts by putting the device’s Amlogic S905Z into Device Firmware Upgrade (DFU) mode, which is done by sending the string “boot@USB” to the board over the HDMI port’s I2C interface. That’s where the HDMI cable comes in: you can cut into one and wire it right up to your Arduino and run the sketch [Exploitee.rs] has provided to send the appropriate command. Of course, if you want to get fancy, you could use an HDMI breakout board instead.

With the board in DFU mode in you gain read and write access to the device’s eMMC flash, but that doesn’t exactly get you in because there’s still secure boot to contend with. But as these things tend to go, the team was able to identify a second exploit which could be used in conjunction with DFU mode to trick the device into disabling signature verification. Now with the ability to run unsigned code on the Fire TV Cube, [Exploitee.rs] implemented fastboot to make it easier to flash their custom rooted firmware images to the hardware.

As with the Fire TV Stick before it, make sure you understand the risks involved when you switch off a device’s security features. They’re often there to protect the end user as much as the manufacturer.

The CatGenie is an amazing device to watch in action, basically a self-cleaning litter box for cats that even does away with the need to replace the litter. It’s comparable to what the indoor flush toilet is for humans compared to maintaining a composting toilet. However, there is a problem. It uses costly soap cartridges which have to be replaced because an RFID reader and a usage counter prevent you from simply refilling them yourself.

CatGenie and Arduino
CatGenie and Arduino

[David Hamp-Gonsalves] reverse engineered the electronics so that he didn’t have to pay for the cartridges anymore. This has been done before and one of those who did it created a product called the CartridgeGenius, but it’s made and sold as a parttime project and there were none in stock. The cartridges have an RFID tag and another solution which we’ve covered before is to replace the RFID reader board with an Arduino. That’s the solution [David] adopted. So why write this post if this isn’t new?

The RFID reader board communicates with the rest of the CatGenie using I2C and he needed to know what was being transmitted. To do that he learned how to use a cheap logic analyzer to read the signals on the I2C wires, which makes this an interesting story. You can see the logic analyser output on his blog and GitHub repository along with mention of a timing issue he ran into. From what he learned, he wrote up Arduino code which sends the same signals. He and his cat are now sitting pretty.

What he didn’t do is make a video. But the CatGenie really is amazing to watch in action as it goes through its rather complex 30-35 minute process so we found a video of it doing its thing, shown at 3.5x speed, and included that below.  If you’re into that sort of thing.

[via Adafruit]

It’s probably fair to say that anyone reading these words understands conceptually how physically connected devices communicate with each other. In the most basic configuration, one wire establishes a common ground as a shared reference point and then the “signal” is sent over a second wire. But what actually is a signal, how do the devices stay synchronized, and what happens when a dodgy link causes some data to go missing?

All of these questions, and more, are addressed by [Ben Eater] in his fascinating series on data transmission. He takes a very low-level approach to explaining the basics of communication, starting with the concept of non-return-to-zero encoding and working his way to a shared clock signal to make sure all of the devices in the network are in step. Most of us are familiar with the data and clock wires used in serial communications protocols like I2C, but rarely do you get to see such a clear and detailed explanation of how it all works.

He demonstrates the challenge of getting two independent devices to communicate, trying in vain to adjust the delays on the receiving and transmitting Arduinos to try to establish a reliable link at a leisurely five bits per second. But even at this digital snail’s pace, errors pop up within a few seconds. [Ben] goes on to show that the oscillators used in consumer electronics simply aren’t consistent enough between devices to stay synchronized for more than a few hundred bits. Until atomic clocks come standard on the Arduino, it’s just not an option.

[Ben] then explains the concept of a dedicated clock signal, and how it can be used to make sure the devices are in sync even if their local clocks drift around. As he shows, as long as the data signal and the clock signal are hitting at the same time, the actual timing doesn’t matter much. Even within the confines of this basic demo, some drift in the clock signal is observed, but it has no detrimental effect on communication.

In the next part of the series, [Ben] will tackle error correction techniques. Until then, you might want to check out the fantastic piece [Elliot Williams] put together on I2C.

[Thanks to George Graves for the tip.]

A good deal of the projects we cover here at Hackaday are not, in the strictest sense, practical endeavors. If we required that everything which graced our digital pages had a clear end result, the site would be in a rather sad state of affairs. Sometimes it’s enough just to do something for the challenge of it. But more often than not, you’ll learn something in the process which you can use down the line.

That’s precisely what pushed [Laurence Bank] to see how well he could optimize the frame rate on the popular SSD1306 OLED display. After several iterations of his code, he was able to achieve a blistering 151.5 FPS, with apparently still some room for improvement if he’s feeling up to the challenge. But considering his first attempt was only running at 5.5 FPS, we’d say he’s already more than earned his hacker cred on this one.

A few different tricks were used to achieve such incredible performance gains. To start with, while the official I2C specification says you’re supposed to wait for an acknowledgment back from the device when communicating with it, [Laurence] realized the SSD1306 didn’t actually care. He could continuously blast commands at the display without bothering to wait for an acknowledgment. He admits there are problems with this method, but you can’t argue with the results.

To really wring all the performance out of the system he could, [Laurence] donned his Assembly Cap and examined how the Arduino IDE compiler was interpreting his code. He identified a few areas where changing his C code would force the compiler to generate faster output. He notes that this wouldn’t normally be required when working with more advanced compilers, but that the Arduino toolchain needs its hand held occasionally.

This isn’t the first time we’ve seen somebody try and push more pixels through the very same OLED display, and it’s interesting to see the two very different approaches to the same goal.

We’re digging these daisy-chainable encoders built by [fattore.saimon]. Each module consists of a rotary encoder attached to a PCB with a PIC16F15386 on the back. As we’ve covered in the past, the Microchip released their feature-rich PIC16 microprocessor just this year, and it’s great to see them start to crop up in projects. With 4 address jumpers on the back of each PCB, [fattore.saimon] is able to connect up to 16 of the encoders on the bus. The modules also have male and female plugs so he can connect them physically as well, to simplify wiring. Each module also has a PWMable bicolor LED for keeping track of each encoder’s setting.

If you’re interested in making your own you can buy the PCBs from Tindie or download the project files from the creator’s GitHub, including an Arduino library.

We love encoders here on Hackaday — building DIY encoders, as well as using them in projects like this precision cutting jig. And definitely read our colleague [Al]’s great piece on encoders.


Filed under: Arduino Hacks

Feel like taking a long walk, but can’t be bothered with carrying your drinks? Have no fear, this  “Follow Me” Cooler Bot is here!

Really just a mobile platform with a cooler on top, the robot connects to smartphone via Bluetooth, following it using GPS. Making the platform involves a little woodworking skill, and an aluminium hub with a 3D-printed hub adapter connects the motors to a pair 6″ rubber wheels with a swivel caster mounted at the rear. A pocket in the platform’s base houses the electronics.

The Arduino Uno — via an L298n motor driver — controls two 12V DC, brushed and geared motors mounted with 3D printed brackets, while a Parallax PAM-7Q GPS Module in conjunction with an HMC 5883L compass help the robot keep its bearing. A duo of batteries power the motors and the electronics separately to prevent  any malfunctions.

Controlling the platform is done on an Android smartphone using Blynk. Ease of use and the ability to set basic commands to be sent to the robot over a desired connection type made it ideal for this helpful little ‘bot.

There isn’t anything more complicated going on — like obstacle avoidance or sophisticated pathfinding — so you kinda need a clear line between you and the cooler. Still, beverage storage is a great feature to add to you tag-along robot companion. It seems to work just fine.


Filed under: Arduino Hacks, gps hacks, robots hacks


  • Newsletter

    Sign up for the PlanetArduino Newsletter, which delivers the most popular articles via e-mail to your inbox every week. Just fill in the information below and submit.

  • Like Us on Facebook