The University of Iowa. Copyright© 2005 A. Kruger 1 Introduction to Wireless Sensor Networks Engineering Issues I 31 March 2005

The University of Iowa. Copyright© 2005 A. Kruger 2 Organizational Monday 4:30-5:20Room 4511 SC Thursday12:30-1:20Room 3220 SC Please note that the room numbers are different for Mondays and Thursdays. Monday5:20-6:20Room 1126 SC Thursday1:30-2:30Room 1126 SC OtherBy appointmentRoom 523C SHL Class Website Class Time Office Hours

The University of Iowa. Copyright© 2005 A. Kruger 3 Issues Interfaces –Mote/MCU radio(s) –Mote/MCU Sensors –Programming mote Temperature & Humidity –Impacts reliability, packaging, stability, –Consumer (0 … 70 o ) –Industrial (-40 … +85 o ) –Automotive, Military Packaging Reliability –Consumer, Medical

The University of Iowa. Copyright© 2005 A. Kruger 4 Interfaces

The University of Iowa. Copyright© 2005 A. Kruger 5 Concept DTE/DCE DTE (The device that generates or requests data) –MCU –Datalogger –PC –Terminal emulator –Mote DCE (The devices that interfaces with the media) –Modem –Radio –Instruments –GPS Important DTE and DCE data rates may differ. Often DTE DCE data rates are larger than data rates between DCEs

The University of Iowa. Copyright© 2005 A. Kruger 6 Concept: Data Rates and Flow Control DTE DCE data rates may exceed DEC DCE rates DCE has internal buffers When buffer is close to full DCE signals DTE to stop sending data When DEC buffer becomes empty, it signals DTE that it can start sending data

The University of Iowa. Copyright© 2005 A. Kruger 7 Concept: Handshaking DTE uses a “Request To Send” (RTS) signal to let DCE know its want to send data DCE uses a “Clear To Send” (CTS) to signal it is ready to send or not Sleep modes –RTS are sometimes used to wake sleeping DCEs

The University of Iowa. Copyright© 2005 A. Kruger 8 Serial Communications RS232/RS232C,RS422, RS485 or TTL Levels USB, USB RS232 adapters DB9, DB25, Two-wire, I2C, SPI Data lines –TX or TD : data is transmitted to a DCE (out from PC) –RX or RD : data is received from DCE (into PC) Control Lines –Hardware Flow Control RTS (Request To Send). DTE (PC) uses this to inform DCE that it wants to send data CTS (Clear To Send) DCE (modem/radio) uses this to inform DTE (PC) when it is clear to send or not CD (Carrier Detect) DTR (Data Terminal Ready) – similar to RTS Software Flow Control – special codes in the data stream (XON/XOFF)

The University of Iowa. Copyright© 2005 A. Kruger 9 RS232 Serial Communications

The University of Iowa. Copyright© 2005 A. Kruger 10

The University of Iowa. Copyright© 2005 A. Kruger 11 Command vs. Data Mode – AT Commands Sending Data & Commands over a serial link –Data (normal) mode –Command (configuration) mode Switch between modes with a special sequence delay +++ delay Issue AT commands ATDT … Switch Back ATCN

The University of Iowa. Copyright© 2005 A. Kruger 12 Serial Communications Misc Cable Lengths Null Modems Gender Changers Loop-back adapters Break-out boxes Cable testers RS232 TTL converters Gotcha’s (not all DB9 cables are RS232) –UPS cables –Some instrument cables

The University of Iowa. Copyright© 2005 A. Kruger 13 Null Modems

The University of Iowa. Copyright© 2005 A. Kruger 14 Null Modem Cont. Full Handshaking Loop back handshaking

The University of Iowa. Copyright© 2005 A. Kruger 15 Loop Back Cables & Adapters

The University of Iowa. Copyright© 2005 A. Kruger 16 Applications Echo Server Streaming Server

The University of Iowa. Copyright© 2005 A. Kruger 17 Lab Next Week Two-three hours –Groups of three students work as a team –Individual reports Signup sheet –Wednesday afternoon –Thursday afternoon –Friday afternoon –Saturday? Preparation –Will post and