Lost Item Pager Project Description Russ Kinley
Introduction The lost item pager will have a base unit that is stationary, consisting of a few page buttons and a digital display. Each of the buttons will page a small pager that is attached to the item you have misplaced. The digital display will show the user which item is being paged and if the item is out of range of the base or beeping. The pager units, when triggered, will have LED s flash and emit a beeping sound that will be locatable to the user. When the lost item is found the button on the pager ends the beeping. Physical Description Base The base of the system will be much bigger than the pagers in order to make it easier to mount on the wall or sit on a desk. The LCD display will be the largest piece of hardware and will set the limit on how small the base can be. The printed circuit board for the MCU and all of the connected parts will not need to be larger than 4in x 3in. There will be three buttons, numbered 1, 2, and 3, three red LEDs each corresponding to a button, a green LED and an LCD display. These components will be spread out on the face of the base and will be soldered to the printed circuit board. The base will be powered using a 5V dc transformer plugged into a standard 120V 60Hz outlet. The green LED will be included to show that power is reaching the unit. Units: inches 1
Pagers The pagers will be about the size of a typical car alarm remote, as shown in the drawing below. The printed circuit board inside will contain all of the connecting hardware and will not need to be larger than 2in x 1.5in. The pagers in this system will run off of a 3V coin sized battery (one in each pager). Included in the pager are two red LEDs, a push button, a keychain hole and a speaker below the pin-holes in the plastic case. The case is slender to fit in one s pocket, with smooth rounded sides and corners to keep the pager comfortable to touch and hold. Functional Hardware Description Units: inches The base and the pager units will use a ZigBee system IC from Freescale, MC1321x, which includes an HCS08 microcontroller and an RF transceiver. The base will use a MC13213 which comes with 4K of RAM and 60K of flash, which will be plenty of memory for this application. The base unit will be using a 2x16, 5x7 LCD screen connected to the MCU by an 8 pin bus. Three push buttons will be included as shown in the drawing above, connected to port B on the MCU; one for each pager. A red LED corresponding to each button will be connected to port D on the MCU. The base will be stationary and plugged into an outlet so it is plausible to have continuous processing in the base requiring no low power sleep mode, but the pagers will be running off of batteries and so will need to be in low power mode most of the time until paged. On the pager an 8 ohm speaker will be included instead of an LCD screen and there will only be one button and two red LEDs. An MC13211 will be used in the pagers instead of the MC13213, because they are a little cheaper due to not as much memory: 1k of RAM 2
and 16k of flash which better fits the application. The pagers will run off of a small 3V coin sized lithium battery. To conserve battery life, the pagers will be in a low power mode most of the time and will wake up when the IRQ pin is set internally on the MCU through the transceiver. Base block diagram: 3.3V 5Vdc 3.3Vdc Power Supply 120Vac-5Vdc 3.3V regulator (500 ma) VDD LEDs 3 Port D PTD4-6 Xtal1-2 4k RAM 2MHZ Buttons 3 Port A PTA2-4 MC13213 60k Flash RFIN_M RFIN_P 5V Port B PTB0-7 8 LCD Vss 3
Pager block diagram: 3V battery Vddint Vbatt LEDs 2 Port D PTD4-5 Port D Xtal1-2 2MHz crystal Button Amp. and Speaker Port A PTA2 Port D PTD2 1k RAM 16k Flash MC13211 RFIN_M RFIN_P Vss Software Description The programming of the lost item pager s MCUs will be done using Freescale s Code Warrior; assembly and C languages. There will be a few program modules in the base used for the I/O routines on the base like displaying ASCII character strings on the LCD, a counter, active detection and a time-slice kernel to control the individual tasks. Just one main module will be used for the pagers. The system communication is relatively simple so I will be using SMAC (simple medium access control) to access between the wireless devices; the software is available from Freescale. The signals sent between the devices will be packets of data accompanied by an address, so that only the desired device actually receives the data or command. The system will have two-way communication between the base and the pagers, to allow useful functions like active detection. The active detection function in the base will pole the pagers once an hour to test if they respond back; this information will be used to display to the user if each pager is responsive (within range) or non-responsive (out of range). 4
The base unit will use a time-slice kernel module to pole the pagers, check for a button press, update LCD display, activate timer and display beeping timer. Only one pager, containing the correct address, will be allowed to activate and beep at a time to help avoid confusion from multiple sources of beeping. The system will be set up for peer to peer data transfers, though the pagers will not communicate with each other. The pagers are going to be in a low power mode most of the time and will need to wake up to receive a message using an IRQ from the transceiver. When each pager wakes up (transceiver returns from hibernate and MCU returns from stop3) the message s address sent from the base will be analyzed, letting the intended pager perform its task while the others return to the low power state. The MCU has a built in programmable Low Voltage Interrupt (LVI) that will be used to put the pager into a reset state when the battery runs low so that the device doesn t act in an unpredictable way due to low input power. To conserve power, a timer will be used on the base which will sent a signal to the beeping pager to return to sleep after five minutes of beeping. Below is a list of the expected modules used in this product: Base: Module Name LCD Display Wireless Page button Device Active Timer Time slice Kernel Pager: Module Name Main Description This will be used for displaying messages on the LCD This module will handle the transmit and receive operations and SMAC software Detect when a button is pressed and determines the next course of operation (state changes) Continuous polling module, determines if pager is responsive Counts in minutes and seconds, how long the page function has being running Creates time for each module or task to operate Description SMAC software and the repeated beeping and flashing tasks User Interfaces The lost item pager will be activated by pressing one of the buttons on the base. The LED on the base, corresponding to the button, will light up and the LCD display will show a message telling the user which item number is being paged. Once the pager starts beeping, a signal will be send back to the base from the pager telling the LCD display to add an item beeping message. The activated pager will have two LEDs that blink along with a locatable beeping sound from the speaker. The pager is deactivated by pressing either the button on the pager or by pressing the same button on the base. If a pager is beeping and another page button is pressed the beeping pager will continue to beep and the other pager will not. The base will tell the user that only one pager can be activated at a time. Both base and pager only have two states of function; the pager is either beeping or conserving energy in low power mode. The base can only either page 5
or wait, but there are seven LCD display messages used throughout the functioning of the base. Base LCD Messages: #1. When the item pager base is not being used, it will remain in the wait state. In this state the LCD display shows the main message shown below, the numbers in the bottom right corner correspond to the pager units that are found responsive to the base. I T E M P A G E R R E A D Y P R E S S B U T T O N 1 2 3 #2. When a page button is pressed, the base will then be in the paging state and the LCD display shows the following message where instead of X the number on the button pressed will appear: P A G I N G # X... #3. If the pager receives the page signal with the correct address, it transition into the beeping state and returns a signal to the base. Then the LCD display will update to this message, where the time in minutes and seconds since the pager started beeping will appear: P A G I N G # X... # X B E E P I N G 0 0 : 0 0 #4. If the base is in the paging state (where either messages #2 or 3 are shown) and the user presses a different page button the message below will appear for 10 seconds before returning to the previous message: O N L Y O N E I T E M A T A T I M E 0 0 : 0 0 #5. If the pager does not receive the page signal (pager out of range or dead battery), no acknowledgement signal will be returned to the base from the pager and the following message will be displayed instead of display #3: P A G I N G # X... N O R E S P O N S E 6
#6. When the button on the beeping pager is pressed, the base returns to the wait state and this message will be displayed: P A G E R # X F O U N D 0 0 : 0 0 #7. If the pager has been clocked at beeping for five minutes or if the same page button was pressed again on the base, the base will return to the wait state the following message is displayed on the screen: P A G I N G # X E N D E D 0 0 : 0 0 After 30 seconds of displaying any of the three messages shown directly above (#5, 6, 7), the base will return to the wait state and the main screen (#1) will reappear as shown below. In this display, pager 1 has been non-responsive (out of range) and pagers 2 and 3 are responsive (in range of the base). I T E M P A G E R R E A D Y P R E S S B U T T O N - 2 3 Base State Diagram Page Button Pressed Wait Display message #1, 6 or 7 shown Polls pagers hourly Waits for user input Paging LCD shows one of page messages either #2,3,4 or 5 Found signal received from pager, same button pressed again on base or the base timed five minutes of beeping 7
Communication Standards and Protocol The MC1321x is designed to meet the IEEE standards set for Zigbee wireless devices, IEEE 802.15.4, which is the short-distance wireless communication standard for 2.4 GHz ISM band. The features of the standard used in this project are data rate of 250kbps, two addressing modes; 16 bit and 64 bit, power management for low power consumption, 16 channels in the 2.4GHz ISM band. The data transferred between the base and pagers will be set up as peer to peer communication sent using SMAC software. The FCC rules and regulations needed for this project are stated under 47 C.F.R. part 15, for unlicensed low power radio frequency communication. The rules encountered in this project are basically stating that the Zigbee parts cannot be manipulated or changed, that interference from the devices must be within a tolerance and if the product is to be marketed it must be tested and inspected by the commission. The prototype I will demonstrate will be designed on a Zigbee evaluation kit which has already been approved by the FCC and meets the IEEE standards. Development Plan Weekly schedule: My prototype will be created on a Zigbee evaluation kit, which is similar to my actual design. Using this kit; one central board with LCD and two smaller battery operated boards, so I should not need to add any hardware. Therefore the bulk of my prototype 8
creation will be software oriented. I will first need to practice some simple programming on the boards to become familiar with how the boards work such as LED lighting and blinking, sound generation and RF transmitting and receiving. There are a few example software programs and tests provided on the Freescale website, which will help me complete my understanding of the boards. I have created a list of a few programs I will be experimenting with and a plan for incorporating all the different parts needed to complete the design and prototype on a weekly schedule for winter and spring quarters: Winter Quarter Week 1 Week 2 Week 3 Week 4 Week 5 Week6 Week 7 Week 8 Week 9 Week 10 Finals Week Spring Quarter Week 1 Week 2 Week 3 Week 4 Week 5 Week6 Week 7 Week 8 Week 9 Week 10 Finals Week Research Zigbee requirements for transmitting Determine which sleep mode is most appropriate Determine good sound frequency signal Design/ find a test program for LEDs and other board operations Finish test programs Begin testing LCD module Continue LCD tests Decide what areas will need more work than others Begin testing RF transmitting/ communication between boards Distinguish best way to wake pagers Further testing Begin finalizing hardware description and design Continue on hardware Finish hardware description and design Hardware Reviews Finalized software flow chart Begin software programming Test and debug Time to program/ clean up code Code Reviews Demonstration Development hardware and software: The software programming will be done using Freescale Code Warrior. I will be using the mixed signal digital oscilloscopes in the ET 340 lab to test pin outputs for the timeslice usage and various functions as the development continues. I will be using the P&E USB multilink interface from Freescale to program the boards from a USB port on the computers in the ET 340 lab. Demonstrating the Prototype: The boards I am using in the development kit are inside plastic cases and should not require any additional hardware. Because the units are encased, I plan on allowing people to come up and try out the system (move the pager units around the room) while I 9
will be there to answer questions and show off its features. In order to show my project to many people a visual prop will be accompanying me at my station. Design Issues The most important issue in my project will be to create a design with excellent battery life, which will depend on the sleep modes available. There are two sleep modes available on the MCU: stop2 and stop3. There will need to be a wireless external interrupt sent from the base to wake up the pagers so that they will receive and process the commands from the base. A trade off of lower power consumption in sleep mode is wake up time, which will delay the response from the pager, but it will be important for the pagers to respond relatively quickly to a signal from the base. Electrical Specifications Project specifications/ Environment Conditions Parameter Condition Units Frequency range 2.400-2.483 GHz Transmit range 75 ft Operating temp 0-50 ºC Pager PCB 2x1.5 in. Base PCB 3x4 in. Speaker output 100 db # of possible pagers 3 47 C.F.R. Sec. 15 RF device requirements FCC Standards IEEE 802.15 Zigbee RF devices IEEE Standard Power Requirements Pager: Power Source size milliamp hrs Pd (ma) cost expected life 3V lithium battery 24.5mm 575 7.9 $1.28 72.8 hrs (beeping) 0.0443 12800 hr (Sleeping) Base unit: Power Source Size (in) milliamp hrs Pd (ma) cost expected life 5V dc switching power supply 2.5 x 1.4 x 1.05-15.9 $4.94-10
Preliminary Parts list: Base Part Part # Quantity Price(ea) Cost Distributor Power Dissipation Lead Time MCU/transceiver MC13211 1 $3.43 $3.43 Freescale 2.1mA 6weeks LCD Display MDLS16268B 1 $8.30 $8.30 Digikey 9mA 6weeks LED (red) 160-1707-ND 3 $0.09 $0.27 Digikey 1mA 2-3weeks LED (green) 160-1706-ND 1 $0.09 $0.09 Digikey 1mA 2-3weeks Quartz Crystal NJU6368 1 $0.25 $0.25 Digikey 0mA 2-3weeks Button EFTL620 3 $0.41 $1.23 Digikey 0mA 2-3weeks antenna - 1 - - - - - Resistors RNF1/2T210K 9 $0.03 $0.27 Digikey 2.7mA 2-3weeks 5V wall transformer T977-P6P-ND 1 $4.94 $4.94 Digikey - 3-4weeks Inductors varies 5 $0.30 $1.50 Digikey 0mA 2-3weeks Capacitors varies 6 $0.30 $1.80 Digikey 0mA 2-3weeks Transformers varies 1 $1.02 $1.02 Digikey 0mA 2-3weeks 3.3V regulator LM2937ET-3.3 1 $0.71 $0.71 National 6weeks Totals: $23.81 15.9mA Pager Part Part # Quantity Price (ea.) Cost Distributor Power Dissipation Lead Time MCU/transceiver MC13211 1 $3.43 $3.43 Freescale 2.1mA 6weeks 8 ohm speaker 1420CM08(GP) 1 $1.00 $1.00 Digikey 1.5mA 2-3weeks LED (red) 160-1707 2 $0.09 $0.18 Digikey 1mA 2-3weeks Quartz Crystal NJU6368 1 $0.25 $0.25 Digikey 0mA 2-3weeks Button EG4375CT-ND 1 $0.41 $0.41 Digikey 0mA 2-3weeks transistor (signal amp) 2N222 1 $0.21 $0.21 Digikey 1.5mA 2-3weeks antenna - 1 - - - - - Resistors RNF1/2T210K 6 $0.03 $0.10 Digikey 1.8mA 2-3weeks 3V Lithium Battery N340-ND 1 $1.28 $1.28 Digikey - 2-3weeks Inductors varies 6 $0.30 $1.80 Digikey 0mA 2-3weeks Capacitors varies 6 $0.30 $1.80 Digikey 0mA 2-3weeks Totals: $9.56 7.9mA 11