The internet of things has created a big market for inexpensive computer boards, so much so that standard open-source designs now have their own clones.
Leland Teschler • Executive Editor
If you eyeball crowd-funding sites such as Indiegogo or Kickstarter you will find several projects aimed at creating computer boards in the format of the Raspberry Pi, BeagleBone Black, or other inexpensive open-source devices. There have been over 11 million Raspberry Pi boards sold since the computer’s release in 2012. The somewhat more expensive BeagleBoard has been around since 2010 and several hundred thousand seem to have sold so far. And there seem to be well over one million Arduino microcontrollers in circulation as well. All these boards originally targeted educational uses but have increasingly been applied in a variety of practical applications.
Much of the open-spec embedded industry has standardized on the interface format for one of these three boards. There are numerous add-on boards available that will work on Raspberry Pi’s 40-pin expansion interface. Ditto for the Linux-ready BeagleBone Black from BeagleBoard.org, containing dual 46-pin connectors. The Arduino layout is also widely used and is a bit notorious because its 14 digital I/O reside on two connectors, so there is an irregular offset between I/O pins seven and eight where one connector ends and the other starts.
All these boards have gone through several revs over the years. The more recent versions have typically added wireless networking schemes of one kind or another, mainly because of the internet-of-things movement. Most clones emerging today also contain numerous wireless radios, but the usual reason for cloning one of these boards isn’t for better wireless facilities. Instead, the goal is to either beef up the ability to handle complicated tasks with more memory and specialized processing abilities, or to enhance the I/O capabilities in ways oriented toward specific applications.
For example, one clone of the BeagleBone Black board comes from SanCloud in the UK. Its version of the BeagleBone Black SBC launched on Indiegogo and starts at $52. Improvements include double the amount of DDR3 RAM found on the original BeagleBone Black. Also on the board are extra USB ports, optional barometer and six-axis gyro, and Gigabit Ethernet.
Over on Kickstarter, there were ten active computer board projects when we recently checked, all aimed at building Raspberry Pi or BeagleBone clones. One such project is a Pi clone developed by UP in the Netherlands. Where the original Pi uses a Broadcom SoC with a quad-core ARM processor, the UP version contains an Intel quad-core Atom processor. The Intel processor lets the UP device run Windows 10 – a feat not possible with any of the ARM versions of the board.
Several other boards and open-source products in this area have debuted in recent months. Interestingly, many them incorporate features that are helpful in applications involved with motors and motion control. Here are a few we found particularly noteworthy.
Board basics
Though the Raspberry Pi has been around for more than five years, new versions still emerge. One of the latest comes from the electronic distributor Premier Farnell Ltd. via its Element14 online community. Element14’s Pi 3 Model B board includes the standard Broadcom BCM2837 64-bit quad-core processor. But the clock speed has been boosted to 1.2 GHz. The board also reflects the recent trend toward wireless connectivity: It contains both WiFi and Bluetooth LE facilities, as well as the usual Ethernet port. Storage facilities consist of the usual 400 MHz 1-GB SDRAM and MicroSD card. The Model B also reflects another trend in Pi boards: It’s power consumption has risen to 2.5 A from a 5-V source. Slower Pi boards lacking WiFi and BLE generally have drawn about 1.8 A.
Peripherals aimed at Pi boards continue to expand as well. A significant number of Pi 
applications turn the Pi into a kind of desktop computing device, so add-ons have emerged that simplify this task. One is the Pi Desktop computer kit based on Raspberry Pi 2 and 3. Also from Element14, it includes a case and an expansion board that can let a Raspberry Pi become a kind of desktop PC. The kit provides an intelligent and safe power controller, a real- time clock, an intelligent on/off switch and an mSATA SSD socket for up to 1 TB of on-board storage. Additional hardware includes a heat sink and various fasteners, spacers, and USB Micro-type A adapter.
One advantage of obtaining peripherals like the Pi Desktop through an entity like Element14 is the relatively extensive online forums surrounding products. Comments posted there about the Pi Desktop, for example, reveal a couple of interesting facts: Lots of Pi users don’t notice the higher current requirements of the newer versions. They power the boards from older supplies and wimpy cables that aren’t up to the new specs, and they experience hard-to-track-down issues as a result. Also, users sometimes have issues with the Pi Desktop because they haven’t flashed the Pi SD card with the latest version of the Debian Linux operating system that runs the Pi. (As of this writing the latest version is “Jessie.”)
As with the continual upgrades of the Raspberry Pi, board makers have extended the BeagleBoard format from its initial mission statement. Recent additions tend to be helpful in application areas focused on robotics and machine control. One version, called the BeagleBone Blue, is built around the same 1-GHz Texas Instruments AM335 processor as BeagleBone Black and carries the same 4 GB for onboard Flash storage and 512 MB of RAM. But it is geared toward motion control thanks to an integrated power management system that lets the board natively host eight 6-V servo controls, four 4-A dc motor outputs, and four encoder inputs. The board also comes equipped with a nine-axis inertial measurement unit and a barometer. Dedicated headers are provided for UART, SPI, DSM2 radio, and even GPS.
The board has a standard USB 2.0 host and client port, useful because there is no dedicated camera or display interface. It is also possible to connect a TFT display via SPI. As with the Raspberry Pi, operating systems load via a MicroSD card. The board supports the Unix-like Debian operating system and the Linux Ubuntu Snappy distributions, as well as robotic-specific OSs and languages like ROS, ArduPilot, and Machinekit.
Similarly, versions of the Arduino microcontroller board now sport features that come in handy for motion control. The current basic Arduino board is called the UNO. It is based on the ATmega328 processor from Atmel and carries 14 digital input/output pins (of which six can serve as PWM outputs), six analog inputs, an ICSP (in-circuit serial programming) header, and a reset button. The Uno differs from older Arduino boards in that it includes an Atmega16U2 programmed as a USB-to-serial converter.
One of the more recent Arduino boards is dubbed the Arduino 101. The most notable thing about it is the substitution of an Intel Curie processor for the traditional Atmel device. There are two tiny cores, an x86 (Quark) and a 32-bit ARC architecture core, both clocked at 32 MHz. The Intel toolchain compiles Arduino programs (called sketches in Arduino parlance) so they distribute optimally across both cores. The processor runs a Real-Time Operating System (RTOS) and framework developed by Intel that is open sourced. The Arduino core communicates with the RTOS to accomplish such tasks as performing PWM.
The 101 includes Bluetooth LE and a six-axis accelerometer/gyro. The board operating voltage and I/O is 3.3 V, but all pins are protected against 5-V overvoltage. Max current draw is 1.5 A. The board can be powered either from the USB connector or an external source.
Finally, there is a chip that is compatible with the Arduino which frequently serves as the basis for simple internet-of-things devices. The chip is the ESP8266 made by Espressif Systems in China. It is basically a WiFi chip but has a microcontroller built in. The CPU is a 32-bit design from Tensilica in the U.S. which runs at 80 MHz. The ESP8266 also contains 16 GPIO pins and interfaces for SPI, I2C, I2S, and a UART.
The ESP8266 CPU and its Wi-Fi components can be programmed like any other Arduino device. One widely used board built on this CPU is called the Feather Huzzah and is made by Adafruit in NYC. This small (2×0.9×0.28-in) board comes with 4 MB of 32-Mbit Flash, 9 GPIO pins, a built-in lithium-polymer battery charger, and a 3.3-V regulator with a 500-mA peak current output. The board works with an Arduino IDE (or NodeMCU firmware with the Lua scripting language) via a USB interface.
The Huzzah is part of Adafruit’s Feather board series. So it can be expanded by combining it with other boards in that series. They include boards for BLE, packet radio, relay controlled power, GPS, stepper and dc motor control, and numerous other functions.
References
Adafruit Feather Huzzah ESP8266
Element14 Raspberry Pi 3
Element14 Raspberry Pi Desktop
Arduino 101
BeagleBone Blue
UP
Libre Computer Le Potato, Raspberry Pi form factor
SanCloud BeagleBone Enhanced
