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FITtape Fitness Information Tracking Tape Measure with Bluetooth Data Syncing Alex Chuang Table of Contents Introduction .................................................................................................................................................. 2 Microcontroller ............................................................................................................................................. 2 System Power ............................................................................................................................................... 2 Battery Pack and Charging ........................................................................................................................ 2 Voltage Output Control............................................................................................................................. 3 Encoder ......................................................................................................................................................... 3 Bluetooth ...................................................................................................................................................... 3 User Interface ............................................................................................................................................... 3 Display ....................................................................................................................................................... 3 Capacitive Touch Interface ....................................................................................................................... 3 Pushbutton Switch .................................................................................................................................... 4 Servo Control ............................................................................................................................................ 4 Bill of Materials ............................................................................................................................................. 5 FITt a p e | 2 Introduction FITtape is a fitness monitoring system that allows the user to easily take body measurements and store them for long-term tracking. It achieves this through the use of a powerful, yet efficient, ARM M0+ core controlling several levels of operation. The FITtape takes length measurement by using a tape on a retracting reel. The system records these measurements using a rotary quadrature encoder and stores them to onboard memory until system is synced to a Bluetooth or USB enabled device. The device also can operate independently of a Bluetooth/USB host device. The FITtape has a super low powered LCD and simple user interface. Microcontroller The MCU in the FITtape is a Freescale Kinetis L MLK25Z128VFM4 ARM M0+ core on a QFN-32 SMD 32pin surface mount package. The microcontroller will be running off its internal clock because the time scale between measurements is 3 to 4 days. It will be able to resync its calendar whenever it connects via Bluetooth or USB. In order to communicate with other modules, it uses the SPI1 ports and chip selects between SPI devices. The two devices running off SPI are the LCD screen and the Bluetooth module. All the other pins are GPIO pins that read input of the encoder, user interface, or output control to the servo system. The FITtape uses 30 of the available 32 pins on the Kinetis chip. The Kinetis L line was chosen for its low power characteristics. When the device isn’t being used after a short period of time, it will go into sleep mode. It wakes on the sleep/power button. The decision to go with the KL25Z128 was due to the memory requirement of the graphic user interface. System Power Battery Pack and Charging The FITtape is a battery powered device running on a Lithium Polymer single cell 500mAh battery. The battery pack comes with its own protection circuit that protects it from overcharge and overdischarge. The maximum charging rate is 150mAh. In order to charge the device, the user will be able to use any standard USB charger. The charge controller is a MCP73831T-2ACI/OT regulates the charge current to 125mAh to stay a safe margin away from the maximum charge rate. The charging circuit also uses a load balancing chip that consists of a p-channel MOSFET, Q1-1, and a zener diode, Q1-2. This allows the 5V of the USB bus to power the device while the battery is charging without interfering with the operation of the charge controller. FITt a p e | 3 Voltage Output Control The FITtape runs on both 3.3V and 5V. In order to achieve this, the FITtape uses two switching regulators. The TPS63001DRCR is a Texas Instruments 3.3V, 1.8A switching Buck/Boost converter with an input range between 1.8 and 5.5V. This powers the MCU, encoder, LCD, and Bluetooth modules. The input range allows for the voltage range of the battery and the voltage input of any USB chrager. The TPS61030PWPR is a 5V boost converter that powers the servo for the measuring tape retracting system. This device has an enable that can disconnect the load from power when not in operation. This feature is ideal for power saving and allowing the use of the small 500mAh battery. Both of these devices were designed using the recommended specifications given by TI. Encoder The AS5035-ASST is a magnetic encoder integrated circuit that outputs a quadrature AB/Index set of pulses. The device operates at TTL and CMOS levels depending on the power driving the device. Since it is being driven at 3.3V, it matches the MCU voltages for GPIO input pulses at 3.3V. The AS5035-ASST has an output resolution of 64 pulses per revolution. This allows for an overall tape measure resolution of 2mm increments, making it the most accurate digital fitness tape measure in the industry. The encoder has a consumption of 500mAh. In order to preventing excessive drain on the battery, the encoder is enabled using a P-channel mosfet in order to reduce power consumption. Bluetooth The 450-0103C Bluetooth module is a one part solution that is FCC compliant. This allows the FITtape to be within compliance without any extra testing. The module communicates with the MCU via the SPI1 channel on port D. The device is powered by 3.3V and has a low power consumption because of the device is focused towards low energy. The Bluetooth power pins have two choke circuits in order to prevent over current. User Interface Display The LCD display is a SHARP LS013B4DN04 transreflective display. It is a super low power display with a 1bit latch for every pixel. This allows the LCD to hold its state without always refreshing. The display is a write-only device on the SPI1 channel and doesn’t have controller so this requires the MCU to buffer the display data. At 96x96 pixels, this requires 1,152 bytes of memory on the MCU be dedicated to graphics output. The display is enabled by pin 28 on the MCU. Capacitive Touch Interface The capacitive touch interface will be built into the body of the device as a glass lay-over of the screen with slider beneath it. This is done using copper electrodes behind the glass to pick up the change in capacitance when a person slides or taps the slider. This inputs to the touch sense interface on the Kinteis L chip. FITt a p e | 4 Pushbutton Switch The pushbutton switch ties to a pin that the Kinetis chip reads to wake from sleep state. When awake, the pushbutton will sleep the device after being held for 1 second. Servo Control The servo is powered by the 5V boost converter and its power draw is controlled by the built in enable of the converter. The KL25Z MCU will output a PWM signal on PTA4 to control the location of the servo. The servo draws .5A so limiting the operation of the servo is of paramount importance. This is achieved by only operating the servo when it needs to be moved, which is only long enough for the servo arm to move 5 degrees. FITt a p e | 5 Bill of Materials Item # Qty 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 18 19 20 21 23 25 26 28 31 32 34 35 40 42 43 45 48 50 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 2 1 2 3 1 2 1 5 2 1 2 3 2 1 Description Battery - 3.7v 500mAh LiPo single cell IC- MCP73831T-2ACI/OT IC - 450-0103C IC- TPS63001DRCR IC- TPS61030PWPR LCD - LS013B4DN04 IC- AS5035-ASST IC -MLK25Z128VFM4 MOSFET - NTHD3101FT1G MOSFET - Si2347DS-T1-GE3 Ferrite Bead - BKP2125HS331-T, 330Ω RGB LED - CLV1L-FKB-CHMMQEHBB7673673 SERVO - T010050, 5V SWITCH - EVQ-Q2B03W, push button tactile CONNECTOR - XF2L-1025-1A CONNECTOR - S2B-PH-SM4-TB(LF)(SN) CONNECTOR - 10118193-0001LF Micro USB B CONEECTOR - 2x5 pin header RES - 100kΩ, 1%, 1/8W, 0805 SMD RES - 300kΩ, 1%, 1/8W, 0805 SMD RES - 33Ω, 1%, 1/8W, 0805 SMD RES - 8kΩ, 1%, 1/8W, 0805 SMD RES - 10kΩ, 1%, 1/8W, 0805 SMD RES - 220Ω, 1%, 1/8W, 0805 SMD INDUCTOR - 2.2uH, 10%, 0805 SMD INDUCTOR - 5.6nH, 10%, 0805 SMD INDUCTOR - 6.8uH, 10%, 0805 SMD CAP - 10uF, 20%, Radial,Can-SMD CAP - 100pF, 20%, Radial,Can-SMD CAP - 220uF, 20%, Radial,Can-SMD CAP - 2.2uF, 20%, Radial,Can-SMD CAP - 1uF, 20%, Radial,Can-SMD CAP - .1uF, 20%, Radial,Can-SMD CAP - 100nF, 20%, Radial,Can-SMD Designator B1 U1 U2 U3 U4 U5 U6 U7 Q1 Q2 FERR_BD1 LED1 M1 SW1 CN4 CN1 CN3 CN2 CN5 R1 R2 R8 R3 R5 R4 R6 R7 R9 R10 R11 L1 L2 L3 L4 C1 C2 C4 C5 C9 C3 C6 C7 C8 C16 C10 C11 C13 C12 C14 C15