DATA COLLECTION USING ZIGBEE 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 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 3 Xbee 1mW w/Chip Antenna zigbee tranceivers 1 XBee Explorer USB 1 Personal computer w/serial terminal 2 pic32mx4 microcontroller experimenter boards

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: I 2 C, SPI, UART Uses Zigbee communication standard IEEE

PIC32MX4 Max Speed MHz: 80 Program Memory Size (KB):512 RAM (KB): 32 A/D channels 16 RTCC Yes UART2

Microcontroller layout Transmitter 1 (z1) Transmitter 2 (z2)

Collection layout Collection Unit

Implementation

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 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 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: r2: 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 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 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 Buying better xbee trancievers 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 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.

Questions