wifi module

• Wi-Fi


  Wireless networking technology that uses radio waves to provide wireless high-speed Internet and network connections
• A common misconception is that the term Wi-Fi is short for "Wireless Fidelity"
• The Protocol

  • Built on the IEEE802.11 standards
  • Wireless Local Area Network (WLAN)
• Consumer Wi-Fi growth (2009-2010)


  • 158% growth in Wi-Fi consumer electronics
  • 90% Wi-Fi enabled cell phones
  • 3 in 4 consumers considered buying a Wi-Fi enabled device
• Embedded Systems

  • Evangelizes on the huge availability of "hotspots"
  • Provides data with a ultra low cost transport
• Wi-Fi communication

  1. A computer's wireless adapter translates data into a radio signal and transmits it using an antenna

  2. A wireless router receives the signal and decodes it

  3. The router sends the information to the Internet Ethernet connection
• Wi-Fi specification

  • Transmit at frequencies of 2.4 GHz or 5 GHz
  • Higher frequency allows the signal to carry more data
• 802.11 networking standards

  • 802.11a
  • 802.11b
  • 802.11g
  • 802.11n
• 802.11a


  • Transmits at 5 GHz
  • Can move up to 54 Mbps
  • Uses orthogonal frequency-division multiplexing (OFDM) to reduce interference
• 802.11b


  • Transmits in the 2.4 GHz frequency band
  • Can handle up to 11 Mbps
  • Uses complementary code keying (CCK) modulation to improve speeds
• 802.11g


  • Transmits at 2.4 GHz
  • Can handle up to 54 Mbps
  • Uses the same OFDM as 802.11a
• 802.11n


  • Newest standard
  • Can achieve speeds as high as 140 Mbps
• Wi-Fi radios

  • Can transmit on any of three frequency bands
  • Can "frequency hop" rapidly between the different bands to reduce interference and let multiple devices use the same wireless connection simultaneously
• There are 13 Wi-Fi channels
• Ad-hoc vs. Infrastructure Networks

  Ad-hoc: Devices connect directly to each other

  Infrastructure: Devices connect through an access point
• UDP

  • Low-level, connectionless
  • No reliability guarantee
  • Faster
  • 2-way handshaking
• TCP

  • Connection-oriented
  • Slower
  • 3-way handshaking (uses communication feedback to open and close)
• WiFly Module

  • Roving's Wi-Fi Solution
  • Industry's lowest power, complete system-on-module solution
• WiFly Module Specification

  • 2.4 GHz IEEE 802.11b/g transceiver
  • Ultra low-power consumption (.4uA sleep, .40mA RX/Connected, 200mA max TX)
  • Embedded TCP/UDP/IP stacks
  • Hardware interfaces (UART, SPI slave, 8 analog sensor inputs)
  • Security (WEP128, WPA-PSK, WPA2-PSK)
  • Real-time clock
  • 1MB flash memory, 2KB NV RAM
• Data Mode

  Default state where WiFly module is a data pipe, transparently handling TCP/UDP headers
• Command Mode

  • Special configuration mode entered by $$$ (Default)
  • Used to assign data such as SSID, IP, pass phrases etc.
  • Configuration settings are stored in the module's flash and persist after power cycling
• Command Mode


  1. Entered by $$$

  2. Performed using ASCII commands

  3. Changes require a reboot to take effect

  4. Commands use a keyword followed by additional information

  5. Case sensitive, no spaces (use "s" instead), shorthand can be used
• Command Mode Commands


  • Set: Immediate effect, permanent if saved

  Get: Retrieve and display stored information

  Status: Display current interface status

  Action: Perform actions like scan, connect, disconnect

  File: Upgrade, load/save config, delete files