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than open source licenses. Hardware and software source files, including schematics, are provided for download. Galileo has good documentation and Intel seeded the community by giving away thousands of boards. The Galileo has some differentiating attributes such as PCI Express (PCIe) and a Real Time Clock (RTC), whereas the RPi has peripherals well-suited for graphicsintensive applications for HD 1080p streaming video. Galileo is a memory-rich, fairly high-performance 32-bit x86 with traits well-suited to embedded portables or wearable devices: small in size (highly integrated), low power, and fairly low cost with respect to the value that is packed in this SoC. Some major differences: RPi has a Graphics Processing Unit (GPU.) Galileo does not. Galileo has an I2C-controlled I/O expander that runs at 200Hz. I/O that runs through the any of the three “GPIO PWM” blocks on the Galileo schematic is going to be limited to only 200 updates per second. IO13 avoids the limitations of the expander, as well as the UARTs, SPI, I2C, and the ADC. Galileo boots from on-board memory. RPi can only boot from the SD card. Galileo has the first PCIe slot supported by Arduino. Cost: Galileo vs. RPi The Galileo board costs almost twice as much as the RPi model B, but there are some hidden costs with RPi, because all that comes in the box is the board. To get RPi running, you need: a USB power supply (at least 700mA at 5V) and an SD card with boot code installed. You may also want a Keyboard, Mouse, HDMI-to-DVI cable (for a monitor),   Galileo   Raspberry  Pi  (Model  B)   DC  Power  Supply  (VIN)   Included.  AC/DC  adapter  with  a   Power  Rating   15W   3.5W  (Model  B)   Ethernet  cable   Cat5e/Cat6;  not  included.     Cat5e/Cat6;  not  included.   USB  2.0  type  A/B-­‐micro  cable   Included.   Not  included.   Mini  SD  Card   Not  required.   At  least  a  4MB,  Class  4  or   Powered  USB  Hub   If  you  require  >2A  for   Table 4: Board Requirements and the informed RPi user will want a powered USB Hub (for parking powerhungry USB devices.) The RPi is not fussy; an old analog TV can be a monitor via the RCA port, but it needs a standard RCA cable. On the other hand, Galileo can be booted and programmed immediately out of the box, since it ships with a USB cable, power supply, and some stand-offs. Galileo boots without the need for external memory like the RPi. Booting the Boards Galileo can boot from on-board memory. The RPi boots only from an SD card (4MB or more), which needs an image that can be found on the Foundation website. Thus, RPi requires formatting a card and copying the image before booting for the first time. Performance Arguably, “performance” is subjective, and depends on what you want to do with the board. Recall that Galileo runs the 400MHz Pentium-class Quark. RPi is normally clocked at 700MHz, but since RPi performs fewer calculations per cycle, they are roughly equivalent in this aspect. The big difference is that RPi includes a GPU as a co-processor and is well suited to work with high definition graphics. The RPi can provide Blue Ray-quality play back. RPi allows itself to be over-clocked, but heat dissipation increases and it might need a fan to prevent erratic operation when overclocked. Galileo sports a 32-bit Pentium ISA-compatible SoC that uses 1/10th the power 2.1mm  center-­‐positive  plug.   Output  rating  of  the  power   adapter  is  5V  at  up  to  3A.   Galileo  must  only  be  used  with   5V  power  supplies.   Not  included.  Micro  USB-­‐plug   charger  providing  5VDC  and  0.7A   (min)  or  up  to  2A  (max  )  if  you   plan  to  use  accessories.   better.   peripherals  powered  via  Galileo.   Recommended  to  power  any   USB  peripherals  that  would  take   RPi  current  draw  above  1A.   of the Intel Atom and a price point within reach of open source projects. Galileo could be applied in remote monitoring, but without a CAN bus, Galileo cannot interface easily with some industrial networks. However, WiFi is available with an adapter on the PCIe slot. Over the last decade or so, embedded processors have begun to interact more with the end user over the internet. Embedded devices have begun to look more like desktops in terms of interaction with people and networking, and the demarcation is getting fuzzy. The line gets more fuzzy with the x86-based Quark in the OSHW community; so much software has already been developed to run on x86 from a desktop point of view. (If you have to program a processor via a host, it’s embedded. Once you install the Linux operating system for use on Galileo, Galileo is a technically a desktop.) Although there is an Open Core movement afoot, OSHW is not always 100% open if the processor chip is not open source. (ARM cores are licensed, but not “open” to reuse without cost.) Some manufacturers make their devices more accessible by allowing users some control over a closed-source chip (e.g., software drivers that allow some manipulation without exposing contents lower in the stack.) Both Galileo and RPi are excellent boards, and they both have the most important feature of all: an established ecosystem with open sources. Mouser Electronics (www.mouser.com) offers the Galileo and many of the products mentioned in this article. Lynnette Reese is a member of the technical staff at Mouser and holds a B.S. in Electrical Engineering from Louisiana State University. http://www.raspberrypi.org/faqs “Overall real world performance is something like a 300MHz Pentium 2, only with much, much swankier graphics.” - http://www.raspberrypi.org/faqs   Galileo   Raspberry  Pi  (Model  B)   USB  2.0   2  ports  (AB  and  B).  USB  2.0  Full   Host  and  Client.    Arduino  library   support  (does  not  convert  USB   input  to  ASCII  for  you.)  3rd  USB   Host  available  over  PCIe.   2  external  ports.  Two  USB  ports   and  share  one  upstream  port  to   the  LAN9512  chip  that  handles   Ethernet  as  well.  Max  current   draw  is  100mA  from  USB  ports,   not  the  expected  500mA.     Ethernet  (RJ45)    10/100  Mbps  with  a  dedicated   PHY  for  Ethernet  control.  One   RJ45  port.   10/100  Mbps  via  a  built-­‐in  USB-­‐ to-­‐Ethernet  adapter.  One  RJ45   port.   WiFi   No.  Can  use  the  PCIe  slot  or  a   USB  port  with  a  USB  adapter  to   obtain  WiFi.    Intel®  Centrino   N135  min-­‐PCIe  wireless  module   is  recommended  by  Intel.   No.  Can  support  WiFi  with  a   USB  adapter,  using  one  USB   port.     SD  Card  Slot   Yes,  a  micro  SD  slot.  Includes  an   on-­‐board  dedicated  SD   controller.     Standard  SD  slot,  min  4GB,  class   4  or  higher.    RPi  must  boot  from   a  portion  of  the  SD  card.     PCIe   Yes,  PCI  Express  mini.    This   enables  WiFi,  SD  card,  USB   Host,  Bluetooth,  or  GSM   (cellular  phone  technology.)     No   TWI/I2C   TWI    means  “Two  Wire  Interface”   Yes   Yes   SPI   Yes.  Native  controller,  Master   SPI  programmable  to  25MHz.   Additional  Slave  SPI  available   only  through  via  a  USB  Client   connector.   Yes   Serial  Data  (UART)   Yes.  Two,  one  is  Tx/Rx  only   ported  as  a  3-­‐pin  RS-­‐232  3.5mm   audio-­‐type  jack.  Programmable.   The  other  has  dedicated  pins.   Yes,  but  no  dedicated  pins;     uses  up  GPIO.   GPIO   Up  to  6  Analog,  Muxed.       Up  to  14  Digital,  of  which       up  to  6  can  be  used  as  PWM.   17  GPIO  pins  (access  to  I2C,   UART,  and  SPI.)  Input  voltage   limited  to  3.3v  only.  26  pin   header  GPIO  interface   Reset  button   Yes   No   DSI  (Digital  Serial  Interface)   No   Yes  (Used  for  char-­‐driven  LCD   displays)   CAN  Bus   No   Yes   GPU   No   Yes   EEPROM   Yes.  11KB.     HDMI   No   Full  HD  1920  X  1080.   DVI   No   No   VGA   No   No   On-­‐board  ADC   Yes.  One  AD7898.  MUXed.           No   Clock   Internal.  Pins  for  an  external   clock,  too.  On-­‐board  RTC.     Camera   No   Header  only.  Expansion   accessory  required.  A  separate   RPi  Camera  board  exists.   Table 3: Comparison of Peripherals/Utilities www.electronics-eetimes.com Electronic Engineering Times Europe February 2014 7


EETE FEB 2014
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