Tag Archives: Arduino shield

Spark Core Weather Station

In my previous blog post I described my first encounter with the Spark Core. Today I want to demonstrate a first simple code example. For this I connected the Spark Core to a Weather Shield from Sparkfun. The shield offers sensors for light, humidity, temperature and pressure. It can even be extended with rain and wind sensors as well as GPS.
.Spark Core Weather
The shield comes with a nice set of libraries and examples that I used as a starting point. To keep things really simple, I combine the entire Weather Shield source with the sensor library functions and the setup() and loop() into a single file. This did not take long and compiled quickly. I also removed the wind and rain related functionality as I did not plan to use those. The source code below takes measurements every second and writes the them to the USB serial port.

For debugging I used the Serial Communication link over USB. Windows users have to install a COM driver. However, MAC and Linux support the Spark Core USB functionality out of the box.

I was really pleased to see how well the Spark Core supports Arduino libraries and well written legacy code. With only a few code modifications I had the sensors up and running.

The setup is now streaming values over a USB cable to a PC. There I captured the values with Tera Term and created a Weather Graph from the comma separated values (CVS). The example below shows the pressure curve of a Bay Area Storm passing by at end of February 2014.
CA Storm
This setup is a somewhat trivial example that a basic Arduino can also do. The project really does not take advantage of the Spak Core's connectivity to the internet. So stay tuned for my next blog post where I will add internet connectivity to the setup.

How does Galileo Stack up against Raspberry PI

I am interested is to compare Galileo and other DIY single board computers. In this post I want to analyze the Galileo board against the popular Rasberry PI. The first thing to note is that the Rasberry PI is not an Arduino compatible platform. However, there are now extension boards available that allow to use Arduino shields with Raspberry PI. Here are to examples: The first is the AlaMode for Raspberry Pi  the second is the GertDuino: Add-On Board for Raspberry PI . Both boards are priced in the range of a Rasberry PI. So the combination of a Raspberry PI with an Arduino shield extension puts this solution right where the Galileo board is.

Have a look at the table below. It compares the two single board computer's hardware. The technical data for the Raspberry PI are taken from WikiPedia.

Rasberry PI Model A Rasberry PI Model B Intel Galileo
Target price: US$ 25 US$ 35 US$69
SoC: Broadcom BCM2835 (CPU, GPU, DSP, SDRAM, and single USB port) Intel Quark X1000
CPU: 700 MHz ARM1176JZF-S CPU 400MHz 32-bit x86 Pentium Class CPU
GPU: Broadcom VideoCore IV @ 250 MHz none
Memory (DRAM): 256 MBytes (shared with GPU) 512 MBytes (shared with GPU) as of 15 October 2012 256 Mbyte
PCIe ports: none PCIe 2.0
USB 2.0 ports: 1 Host 2 Host (from LAN9512) 1 Host,
2 Device
Video input: A CSI input connector allows for the connection of a RPF designed camera module none
Video outputs: Composite RCA (PAL and NTSC), HDMI (rev 1.3 & 1.4), raw LCD Panels via DSI none
Audio outputs: 3.5 mm jack, HDMI, and, as of revision 2 boards, I²S audionull none
Onboard storage: SD/MMC/SDIO 3.3V card slot SD/MMC/SDIO 3.3V card slot
Onboard network: None 10/100 Ethernet (from LAN9512) 10/100 Ethernet
Low-level peripherals: 8 × GPIO, UART, I²C bus, SPI bus with two chip selects, I²S audio +3.3 V, +5 V, ground 16 × GPIO,
UART, I²C bus, SPI
Power ratings: 300 mA (1.5 W) 700 mA (3.5 W) 550 mA (1.9-2.2W)
Power source: 5 volt via MicroUSB or GPIO header 5 Volt
Size: 85.60 mm × 53.98 mm (3.370 in × 2.125 in) 106.68 mm x 71.12 mm (4.2 in x 2.8 in)

The Raspberry PI uses a SoC chip that was originally designed for the set-top box market. Therefore it shows a nice lineup of features on the video side. The integrated HDMI port and on-chip graphics accelerator are testimony to this. However for IoT applications the Quark X1000 SoC used by Galileo offers a really nice selection of interfaces.

What shields are working with Galileo

In my last post I touched on Galileo's shield interface implementation. 010511_0750_0082_nsmsHaving experimented with a few shields sitting in my drawer, I realized that the implementation of the Arduino shield interface creates a bit of a challenge.  So before you assume that a shield is plug-and-play do your homework. Like with a vintage car they may need some tender loving care.

Here are a few key criteria that you want to check:

  • Hardware
    1. Does my shield draw a lot of current: the Cypress CY8C9540A 40-Bit I/O Expander is only capable of driving 15/25mA instead of 40/50mA
    2. Are you accessing some of the shield pins at a high rate? Without special tricks, the Galileo can only toggle an IO pin at 477 kHz (see also Galileo FAQ and Forum post on this subject).
  • Software
    1. Does the driver directly access Atmel's  registers? This can be either the IO-port registers, Interrupt, Pulse Width Modulator (PWM) or Timer registers.
    2. Does it use any  AVR libraries? These libraries are exposing the Atmel AVR hardware to the programmer and are therefore a sure sign that you are in for some work to port the Arduino software libraries to the Galileo platform. Search for "#include <avr/" to see how many AVR hardware specific libraries are used.

Well written software libraries only use the official Arduino application programmers Interface (API). However, many of the existing shield libraries directly manipulating AVR hardware registers. This is either done out of ignorance for software portability or out of necessity as to push the hardware to its limits. I expect that with the transition away from the 8-bit AVR (ATmega328) micro controller to the more powerfule 32-bit CPUs ( Arduino Due, Arduino TreGalileo and Olimex-STM32) this problem will gradually subside.

Also note that as of this writing the following Arduino Libraries are supported:

  • SPI
  • EEPROM
  • UART
  • GPIO
  • WiFi

Check the Release Notes on Intel's site for the latest status.

Galileo is different, is it?

There a quite a number of Arduino boards available. The original Arduinos all used 8-bit AVR micro-controllers from Atmel. Recently Arduino adopted 32-bit ARM cores. In this post I want to look at the features of the Galileo board. The Board is about double the size of an original Arduino board and built around the Intel Quark X1000 controller.Galileo-circuitry_610x534 The Quark family of Intel chips are the new low cost line of x86 controllers that are positioned below the Atom cores.  Quarks are elementary particles that make up the atomic nucleus. Intel positions the Quark family for Internet of Things (IoT) applications. The X1000 controller is the first member of this line. The X1000 offers:

  • 400 MHz 32-bit x86 CPU
  • 512 Kbyte ECC protected embedded SRAM
  • Up to 2Gbyte external ECC protected DDR3 memory
  • 10 /100 Mbps Ethernet port with RMI interface
  • 2 x PCI Express Rev 2.0 ports offering up to 2.5 GT/s data transfer rates
  • 2 x USB 2.0 Host ports
  • 1 x USB 2.0 Device port
  • SDIO card interface
  • 2 x I2C Master interfaces up to 400 Kbit/s
  • 16 x GPIO
  • 2 x SPI Master controllers
  • 2 x 16550 compliant UART supporting baud rates from 300 to 2764800
  • Real Time Clock (RTC)

The controller is packed into a Flip-Chip Ball Grid Array (FCBGA) package with 393 solder balls that come with a 0.593 mm ball pitch. The package dimensions are 15mm x 15mm. With this kind of a package hand soldering is out of the picture.

Noteworthy is the implementation of the Arduino shield interface. The interface is pretty much designed with external components. For the GPIO/PWM digital shield pins a Cypress CY8C9540A 40-Bit I/O Expander with EEPROM  is used. The analog shield pins use an Analog Device AD7298 8-Channel, 1 MSPS, 12-Bit SAR Analog to Digital Converter (ADC) with Temperature Sensor . The Quark controller uses I2C serial interface to control the PGIO/PWM CY8C9540A device and the SPI for the ADC AD7298.