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Data Collection U sing Z igbee Network. Timothy Melton Moscow, ID. Introduction. Problem: I wanted a way to monitor analog inputs to microcontrollers using a zigbee wireless network with a central gathering point

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Data collection u sing z igbee network

Data Collection Using Zigbee Network

Timothy Melton

Moscow, ID


Introduction
Introduction

  • Problem: I wanted a way to monitor analog inputs to microcontrollers using a zigbeewireless network with a central gathering point

  • Solution: Using three xbee brand transceivers and two pic32 microcontrollers I was able to setup a short range network for data monitoring and collection


Hardware
Hardware

  • 3 Xbee 1mW w/Chip Antenna zigbeetranceivers

  • 1 XBee Explorer USB

  • 1 Personal computer w/serial terminal

  • 2 pic32mx4 microcontroller experimenter boards


Xbee transceiver
Xbee Transceiver

  • RF Data Rate: 250 kbps

  • Indor/Urban Range:100 ft (30 m)

  • Transmit Power: 1 mW (+0 dBm)

  • Frequency Band: 2.4 GHz

  • Interfaces: I2C, SPI, UART

  • Uses Zigbee communication standard

    • IEEE 802.15.4


Pic32mx4
PIC32MX4

  • Max Speed MHz: 80

  • Program Memory Size (KB): 512

  • RAM (KB): 32

  • A/D channels 16

  • RTCC Yes

  • UART 2


Microcontroller layout
Microcontroller layout

Transmitter 2 (z2)

Transmitter 1 (z1)


Collection layout
Collection layout

Collection Unit





Configuration
Configuration

  • Microprocessor recievers

    • Set as endpoint device on network

      • Harcoded to send to router

    • UART to transceiver

    • 9600 BAUD

    • No flow control, 8-bit, no-parity, 1 stop bit

    • UART receive interrupt

  • Collector

    • Set as router

      • Broadcast messages

    • Transceiver to serial

    • Matching serial configuration in terminal


Method
Method

  • Microcontroller units

    • Addressed z1 and z2

    • Read ADC measurements every second

    • Attach time to the measurments

    • Use fprintf statement to write to a buffer

    • Record past three readings

    • Wait for go signal from collector

    • Broadcast last three readings

  • Collector

    • Broadcasts go command with specific address

    • Recieves data from zigbee through uart into terminal

    • Displays readings in terminal


Method continued
Method Continued

  • Since the microcontroller has a realtime clock and calendar getting the time was a matter of initalizing the time and then polling and storing it to a variable for the printf function

  • A polling timer was setup to check whether the one second ADC sample delay was met

  • To put the packet together for sending:

    fprintf(uartbuff, “z1:: %d:%d - r1:%5.3f r2:%5.3f r3:%5.3f\r\n” hour, min, adc1, adc2, adc3);

    “z1:: 14:22 – r1:01.334 r2:02.454 r3:05.287”

  • packet is generated each time the adc is read

  • Uartbuff3 = uartbuff2; uartbuff2 = uartbuff;

  • then assign to uartbuff each time through to keep track of last three readings.


Method continued1
Method Continued

  • The Collector will send out command:

    zx go

    where x is the microcontroller address

  • A UART receive interrupt is generated in both receivers

  • Receivers parse which receiver is getting the go signal

  • Appropriate receiver sends three buffers to collector


Problems
Problems

  • Configuring XBEE transceivers

    • Firmware flashing issues

      • Only certain available firmwares were able to be flashed

    • Working firmware limited network setup

      • Only able to implement router and endpoint configuration

    • Support for newer firmware hidden


Areas for improvement
Areas for Improvement

  • Buying better xbeetrancievers

    • Newer models

      • Support more features (xbee pro, encryption, mesh networks)

    • More expensive models

      • Support longer ranges and have more antennae options

  • Collector time logging

    • Takes the burden off of the micro for keeping track of time

    • Prevents transmitting data from interfering with time information

    • Would keep track of when received instead of when gathered

  • Writing a program to collect data

    • Enables better storage options

      • Terminal outputs to screen

      • Enables parsing of data for better usage/readability


Conclusion
Conclusion

  • Zigbee provides many options for setting up wireless networks

  • UART communication is an effective means to interface with transceivers

  • PIC32MX4 is very capable of receiving analog inputs and packetizing the data to be transferred over Zigbee.



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