Choosing The Right RTC For Your Project

September 30, 2020 by Lewin Day 27 Comments

When it comes to measuring time on microcontrollers, there’s plenty of ways to go about things. For most quick and dirty purposes, such as debounce delays or other wait states, merely counting away a few cycles of the main clock will serve the purpose. Accurate to the tens of milliseconds, they get the average utility jobs done without too much fuss.

However, many projects are far more exacting in their requirements. When you’re building a clock, or a datalogger, or anything that relies on a stable sense of passing time for more than a few minutes, you’ll want a Real Time Clock. So called due to their nature of dealing with real time, as we humans tend to conceive it, these devices take it upon themselves to provide timekeeping services with a high degree of accuracy. We’ve compiled a guide to common parts and their potential applications so you can get things right the first time, every time.

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Hacking A Cheap Action Cam Into A Dashcam With A Microcontroller

September 25, 2020 by Danie Conradie 15 Comments

Repurposing commodity electronics is one of the true forms of hacking, and it’s always the simple little hacks that lead to big ones. [Everett] wanted to use a $20 GoPro clone as a dash cam, so he wired a microcontroller into it to automate some actions and make it practical.

The camera turns on automatically when connected to external power like a car charger, but starting and stopping a recording and power down all had to be done manually. [Everett] wanted to automate these functions, so he opened up the camera and started probing with an oscilloscope. He found the power button, record button, 3.3 V and external 5 V traces conveniently next to each other in the top of the camera.

To automate the required functions, he wired in a PIC10 on a small breakout board, powered by the 3.3 V line. It detects if 5 V is connected to the charging port on start-up via an N-channel FET, then automatically starts a recording. When the 5 V power is switched off with the car, it waits 10 seconds before stopping the recording and switching off the camera. If no external 5 V is not detected on start-up the microcontroller does nothing, which allows the camera to be used as a normal handheld. [Everett] mounted the camera to his rearview mirror with a magnetic bracket made using a combination of a 3D printer and 3D pen.

This is a simple and practical little hack, and the firmware is available on Github. Cheap dashcams are available for similar prices, but you won’t get any hacking satisfaction that way.

The very nature of actions cameras inspire hacking. You can simply add an external battery with the help of a 3D printer, or go all out and build a gimballed helmet cam from scratch

Putting The Firmware In Your Firmware

September 15, 2020 by Kerry Scharfglass 12 Comments

Performing over-the-air updates of devices in the field can be a tricky business. Reliability and recovery is of course key, but even getting the right bits to the right storage sectors can be a challenge. Recently I’ve been working on a project which called for the design of a new pathway to update some small microcontrollers which were decidedly inconvenient.

There are many pieces to a project like this; a bootloader to perform the actual updating, a robust communication protocol, recovery pathways, a file transfer mechanism, and more. What made these micros particularly inconvenient was that they weren’t network-connected themselves, but required a hop through another intermediate controller, which itself was also not connected to the network. Predictably, the otherwise simple “file transfer” step quickly ballooned out into a complex onion of tasks to complete before the rest of the project could continue. As they say, it’s micros all the way down.

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Turning The Raspberry Pi Into A MCU Programmer

September 5, 2020 by Tom Nardi 42 Comments

Once you graduate beyond development boards like the Arduino or Wemos D1, you’ll find yourself in the market for a dedicated programmer. In most cases, your needs can be met with a cheap USB to serial adapter that’s not much bigger than a flash drive. The only downside is that you’ve got to manually wire it up to your microcontroller of choice.

Unless you’re [Roey Benamotz], that is. He’s recently created the LEan Mean Programming mAchine (LEMPA), an add-on board for the Raspberry Pi that includes all the sockets, jumpers, and indicator LEDs you need to successfully flash a whole suite of popular MCUs. What’s more, he’s written a Python tool that handles all the nuances of getting the firmware written out.

After you’ve configured the JSON file with the information about your hardware targets and firmware files, they can easily be called up again by providing a user-defined ID name. This might seem overkill if you’re just burning the occasional hex, but if you’re doing small scale production and need to flash dozens of chips, you’ll quickly appreciate a little automation in your process.

Of course, if you’re just trying to flash some code in a pinch, there are some more expedient options out there. We’re particularly fond of using a development board to program the bare MCU.

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Pause Your Tunes When It Is Time To Listen Up!

September 2, 2020 by Brian McEvoy 9 Comments

“Sorry. I had music playing. Would you say that again?” If we had a money-unit every time someone tried talking to us while we were wearing headphones, we could afford a super-nice pair. For an Embedded C class, [extremerockets] built Listen Up!, a cutoff switch that pauses your music when someone wants your attention.

The idea was born while sheltering in place with his daughter, who likes loud music, but he does not want to holler to get her attention. Rather than deny her some auditory privacy, Listen Up! samples the ambient noise level, listens for a sustained rise in amplitude, like speech, and sends a pause signal to the phone. Someday, there may be an option to route the microphone’s audio into the headphones, but for now there is a text-to-speech module for verbalizing character strings. It might be a bit jarring to hear a call to dinner in the middle of a guitar riff, but we don’t like missing dinner either, so we’re with [extremerockets] on this one.

We don’t really need lots of money to get fun headphones, and we are not afraid of making our own.

Bike Computer Powers On Long After Your Legs Give Out

August 20, 2020 by Brian McEvoy 13 Comments

A typical bicycle computer from the store rack will show your speed, trip distance, odometer, and maybe the time. We can derive all this data from a magnet sensor and a clock, but we live in a world with all kinds of sensors at our disposal. [Matias N.] has the drive to put some of them into a tidy yet competent bike computer that has a compass, temperature, and barometric pressure.

The brains are an STM32L476 low-power controller, and there is a Sharp Memory LCD display as it is a nice compromise between fast refresh rate and low power. E-paper would be a nice choice for outdoor readability (and obviously low power as well) but nothing worse than a laggy speedometer or compass.

In a show of self-restraint, he didn’t try to replace his mobile phone, so there is no GPS, WiFi, or streaming music. Unlike his trusty phone, you measure the battery life in weeks, plural. He implemented EEPROM memory for persistent data through power cycles, and the water-resistant board includes a battery charging circuit for easy topping off between rides.

When you toss the power of a mobile phone at a bike computer, someone will unveil the Android or you can measure a different kind of power from your pedals.

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Gaming In Different Languages

July 7, 2020 by Bryan Cockfield 2 Comments

One of the perks of using older hardware is its comparative simplicity and extensive documentation. After years or decades of users programming on a platform, the amount of knowledge available for it can become extensive. This is certainly the case with the 6502 microprocessor, used in old Apple computers and some video game systems from the ’80s. The extensive amount of resources available make it a prime candidate in exploring various programming languages, and their advantages and disadvantage.

This project looks into those differences using a robot game, which has been programmed four different ways in three languages. [Joey] created the game in Python first and then began to port it to the 65C02, a CMOS variant of the 6502. The first iteration is its assembly language, and then a second iteration with optimized assembly code. From there, he ports it to C and then finally to Forth. Each version of the game is available to play in a browser using an emulator to run the 6502 hardware.

Since the games run in the browser, other tools are available to examine the way the game runs in each language. Registers can be viewed in real time, as well as the values stored in the memory. It’s an interesting look at an old piece of hardware and of its inner workings. For an even deeper dive into the 6502, it’s possible to build a working computer on breadboards using one.