Tuesday, August 12, 2014

Linduino: USB-Isolated Arduino, Working With DACs and ADCs

Linear Technology products, including ADC & DAC
So a lot of microcontroller (MCU) topics I write about in this blog are mini-research projects for me, because I'm new to MCUs and to electronics in general. Through my research I get to learn more about MCUs and how they're used, and, with a little luck, you get to be informed or amused, or both, by the posts here. But today's topic, Linduino, DACs and ADCs, is even further than normal from my experience and knowledge base, so this post will just give you an overview of the Linduino board from Linear Technology.

"Linduino is a USB-isolated Arduino," an August 11 post on EDN.com, caught my interest because of the *duino name and because the post mentioned applications involving temperature sensors (Humboldt MCU Garden project), audio systems (Humboldt Laser Harp and other music-light instruments) and car systems (Ed Smith is a great resource for vehicle-related MCU projects, possibly something with on-board diagnostics, or OBD). Familiarity with the Linduino board isn't required to do any of the aforementioned Humboldt MCU projects, but at some future point a Linduino could provide major benefits for us. If nothing else, it would be worthwhile to connect with some of the *duino people at Linear Technology, the manufacturer of the Linduino, to expand and strengthen the statewide and worldwide network of the Humboldt MCU community. Plus, their headquarters are in Milpitas, California, so maybe they'll get the urge to drive north behind the redwood curtain and participate in a Humboldt Microcontrollers Group meeting or a Humboldt Makers meeting!
Linduino board

Onward to tech specifics about Linduino. The EDN blog post mentioned above says:
"My pals over at Linear Technology have developed the Linduino board to drive their ADCs (analog to digital converters) and DACs (digital to analog converters) as well as temp sensors and other devices...in addition to the normal shield headers on an Arduino, there is a header that Linear Tech has used for years to drive their demo boards. This computer interface function used to be done with their DC590 interface board. Indeed, the firmware that comes shipped with the Linduino emulates that board, so you can run the original Linear Tech interface program on your PC...The Linduino board will accept all the shield mezzanine boards for Arduino, but has this extra header to control Linear Tech demo boards...Linear Tech also used one of their USB isolators on the Linduino board. This means that the board and what you plug into it are galvanically isolated from the computer you have the USB plugged into. This means you can measure things off a car or an audio system without worrying about ground loops polluting the measurement...Since Linear Tech is also a power supply chip company, they beefed up the power supply on the board, using a switching regulator to replace the linear regulator on the Arduino. This means you can get 750mA out of the power system. Since a USB can’t supply this much power, that means you have to feed the board with an external wall wart. Now you have the power to drive actuators or other heavy loads..."
We're in the early stages of refining the Humboldt Laser Harp, and depending how deep we get into developing the Humboldt family of laser harps and other light-music MCU instruments, there may come a time when we'll need, or at least want, a board that can be used on "an audio system without worrying about ground loops polluting the measurement." That's one of the reasons I am interested in the Linduino board.

The main Linduino webpage has lots of info and links about the board, including several internal blog posts and an overview video about Linduino. Since getting two viewpoints about what the board is and does might help you better understand its value, here's the Linear Technology webpage description of what Linduino is:
"Linduino is Linear Technology’s Arduino compatible system for developing and distributing firmware libraries and example code for Linear Technology’s integrated circuits. The code is designed to be highly portable to other microcontroller platforms, and is written in C using as few processor specific functions as possible. The code libraries can be downloaded by clicking the Downloads tab above and used as-is in your project or individual code snippets may be viewed in the Code section of a supported part. The Linduino One board (Demonstration Circuit DC2026A) allows you to test out the code directly, using the standard demo board for the particular IC. The Linduino One board is compatible with the Arduino Uno, using the Atmel ATMEGA328 processor. This board features a 14-pin “QuikEval” connector that can be plugged into nearly 100 daughter boards for various Linear Technology parts, including Analog to Digital converters, Digital to Analog Converters, high-voltage power monitors, temperature measurement devices, RF synthesizers, battery stack monitors, and more."
Humboldt Laser Harp and Ed Smith
Linduino is not inexpensive, so participants of the Humboldt Microcontrollers Group won't be buying them on a whim like a $3 Arduino Micro clone from China. But if someone has a genuine need for the board, especially a business-related, revenue-generating need, it would be good to know it's available. You can order the board from this Linear Technology page, and there are two options. One option is the DC2026A-KIT for $125, and the other is just the DC2026A board for $75. Digi-Key, Newark and Arrow are also distributors for Linear Technology.

So now you have a general idea of what the Linduino board is and can do, and you've got links above that lead to more info about this member of the continually-expanding *duino family. I'll have to check in with Ed Smith to find out exactly what value this tool might have for us while working on the Humboldt Laser Harp, the Humboldt MCU Garden or any other MCU projects our MCU group or maker group gets involved with.


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