Tutorial: Booting the NXP i.MX RT from Micro SD card


Erich Styger has written an article on how to boot the NXP i.MX RT from Micro SD card:

It is a common thing to boot a Linux system (see the Raspberry Pi) from a micro SD card. It is not that common for a microcontroller. The NXP i.MX RT ARM Cortex-M7 fills that gap between these two worlds. No surprise that it features a ROM bootloader which can boot from a micro SD card.
Booting from a SD card is kind of cool: load a new software to the card, insert it and boot from it. In some applications this can be very useful: in my configuration the processor starts the ROM bootloader, then loads the image from the SD card into RAM and then runs it. In that configuration no internal or external FLASH memory would be needed.

Via MCU on Eclipse.

App note: Increasing accuracy in feedback circuits and voltage dividers with thin film chip resistor arrays


App note from Vishay on using chip resistors to achieve long-term stability. Link here (PDF)

Thin film chip resistor arrays consist of several resistors of equal or different values combined in one package. During the manufacturing processes and the device’s lifecycle, all the particular resistors virtually experience identical conditions, which allow the specification of their relative tolerances, relative temperature coefficients, and even a relative resistance drift. These relative parameters provide precise and stable resistance ratios and far better long-term stability of feedback circuits and voltage dividers compared to discrete resistors.

App note: Custom magnetics – What are they and when do you need them?


Consideration factors before going to custom magnetic request from manufacturer, an app note from Vishay. Link here (PDF)

There are many manufacturers that claim they build custom magnetics. However, there is often confusion as to what constitutes custom magnetics and whether or not a designer actually needs them or can afford them. This article will clarify what custom magnetics are, help designers determine if they are needed, and explain how to engage with a custom magnetics supplier.

The Boris Beacon – A 1mW solar powered hifer beacon


Dave Richards (AA7EE) has written an article detailing his 1mW solar-powered HiFER beacon project, the Boris Beacon:

In this post from May of last year, I detailed the construction of a 1mW solar-powered HiFER beacon. I named it the Boris Beacon, in tribute to my neighbor’s cat. The beacon was never mounted permanently outside. I kept it indoors, powered from a small solar panel in the window, and feeding an “antenna” of sorts, consisting of the original dipole wires folded up into two small bundles. Obviously, I had no serious intention of it being heard by anyone; I just liked having it come on every day when the sun came up, and transmitting until later in the day, when the light was too low to sustain operation.

See the full post on his blog.

Viewing ARM CPU activity in real time


Jeremy Bentham writes:

In previous blog posts, I have described how an FTDI USB device can be programmed in Python to access the SWD bus of an ARM microprocessor. This allows the internals of the CPU to be accessed, without disrupting the currently running program.
In this blog I take the process one step further, and add a graphical front-end, that shows the CPU activity in real time

More details on Iosoft blog. Source files are available on GitHub.

DIY Arduino based RC transmitter



Dejan over at HowToMechatronics posted a detailed how-to on building DIY Arduino RC transmitter:

Now I can wirelessly control any Arduino project with just some small adjustments at the receiver side. This transmitter can be also used as any commercial RC transmitter for controlling RC toys, cars, drones and so on. For that purpose it just needs a simple Arduino receiver which then generates the appropriate signals for controlling those commercial RC devices. I will explain how everything works in this video through few examples of controlling an Arduino robot car, controlling the Arduino Ant Robot from my previous video and controlling a brushless DC motor using an ESC and some servo motors.

More details on HowToMechatronics’ project page.

Check out the video after the break.

PLA dielectric strength measurement

PLA Dielectric Strength Measurement

Kerry Wong did some experiment measuring the dielectric breakdown voltage of PLA:

In my previous post, I designed and 3D printed a high voltage connector for my Bertan 225-20R high voltage power supply. The silicone high voltage wire I ordered had finally arrived so I made a couple of cables using the connectors I printed. A few of my viewers had questioned the suitability of using PLA as printing material in high voltage applications so I decided to measure the dielectric breakdown voltage of PLA and gather some real-world data.

See the full post on his blog here.

Check out the video after the break.

App note: Simplify home audio systems With the PCM9211 – A versatile audio interface transceiver


A digital interface PCM9211 from Texas Instruments app note. Link here (PDF)

Large-screen HDTVs are selling in huge volumes over last few years, primarily driven by amazing improvements in picture quality & form factor (thinner screens). The form factor constraints from having skinny screens result in tiny built-in speakers that are undersized, under-powered and are typically aimed at wrong direction. Hence sound bars have exploded in popularity as complementary audio system by providing a sound experience that more closely matches the TV’s life-like pictures. In addition, with release of HDMI 2.1 specification we finally have a nocompromise audio solution for HDMI as part of the eARC [enhanced Audio Return Channel]. This tech note reviews eARC and simplified Sound Bar design using PCM9211 and how to interface eARC signals with PCM9211.

App note: Noise suppression for wireless headphones


Wireless headphone interference investigation from muRata. Link here

Recently, the popularity of wireless headsets has been growing as the number of situations where people “play sports while listening to music” increases.

Bluetooth is frequently used for communication between smartphones and headsets. However, audio can skip due to communication errors, so countermeasures are required.

This is an extremely important point of user evaluation and a difficult issue to resolve.
Here we depict an actual case to explain the interference mechanism in the device which causes the audio to skip, and key points for improvement to introduce useful countermeasures for solving the problem.
We hope that you will use it as a guide to help your design work proceed more smoothly.

MusiCubes project


Michael Teeuw published a new build:

Now that the MusiCubes tray is assembled and the RFID-sensor and LEDs are working as expected, It’s time to add the last feature of the original concept: invisible capacitive touch sensors to control the volume of the music.

See the full post on Xonay Labs blog. Be sure to see Part 1 and 2.

Check out the video after the break.