OP4-ATS-TX418lower limb force monitoring device

123456 A B C D 654321 D C B A Title NumberRevisionSize B Date:2-Sep-1999 Sheet of File:C:\FCCCERT\TXBLOCKD.SCHDrawn By: ADC1 ADC2 AMPS DAC Sensor Memory Calibration Connector Transmitter Network Matching Circuit PCB Trace Antenna Battery DC to DC Converter Microcontroller +3.3V +3.3V +3.3V +3.3V +3.3V +3.3V Transmitter Block Diagram A 1 of 1 Rainer Riffert LBILBO 2.7V Threshold Detection 1.6V Threshold Detection Power Supply Shut Down 9600 baud Data PacketsRF RF Out Pulsed Power to Sensor Battery Pack Including Antenna (1.6 to 3.3 Vin) Vout Setup and Calibration Data Computer Calibration and COM Port Bridge Strain Gage CPU Main Program

2 FCC ID: OP4 – ATS – TX418 This device complies with part 15 of the FCC Rules. Operation is subject to the following two conditions: (1) This device may not cause harmful interference, and (2) this device must accept any interference received, including interference that may cause undesired operation. OTR, Inc. Knoxville, TN

Description of Shoe Transmitter Operation (Brief). The transmitter electronics is part of a weight bearing shoe product that senses a weight by analog means. The microcontroller converts this signal to an 8 bit digital word. The microcontroller then transmits the word along with a shoe address, Hi/Lo battery indicating bit, and error code correction to a receiver in a train of bursts at a rate 20 per second. An individual burst duration is a little less than 9 ms, and the duration of the train of bursts last for as long as a weight of 10 Lbs. or greater is applied to the force plate. It is a user actuated device and is used while walking for orthopedic patients or patients that need to monitor their weight to one limb. The product unit is to be sold as 3 size shoes, small, medium, and large i.e. 3 transmitters operating identically in the same fashion as described here only with a different shoe address for the different shoe sizes, and a receiver. In some instances it may be required of us to provide up to as many as 32 shoes/shoe addresses per receiver. Moderately Detailed Circuit Description. Power is applied in the form of 2x1.5 Volt AAA batteries i.e. (a voltage that ranges from less than 1.6 to about 3.3 Volts). This in turn supplies a DC to DC converter, which generates a stable 3.3 Volts. This voltage then supplies power to the microcontroller, which then begins the start up process. It then collects data stored in a memory to identify itself by a shoe address and it reads the calibration data. The program then goes into operation mode. The program at a rate of 20 times a second first wakes up the amplifiers and then sends an 8 bit digital word to the DAC to set the amplifiers offset to the proper value. The microcontroller then pulses the power to the sensor and then takes a reading and converts it to a digital word. This digital word is then corrected by a calibration multiplying factor to adjust the gain due to inaccuracies of part tolerances in the manufacturing of the various passive and active analog parts of the sensing circuitry. This new corrected 8 bit digital word is then evaluated to see if the weight has exceeded 10 Lbs. in which case the word is then merged with the shoe address, Hi/Lo battery indicator bit, error code correction, and then is sent to the transmitting chip. This information is then sent in on/off keyed bursts at a carrier frequency of 418Mhz. Each burst is about 8.5 ms long and continues 20 times per second as long as there is a weight of 10 Lbs. or greater on the force plate of the shoe. The microcontroller is also looking for inactivity in which case the microcontroller after 1 minute of inactivity will shut down the DC to DC converter/power supply and then go to sleep as long as the battery voltage stays above 2.7 Volts. The microcontroller then feeds off the batteries directly in sleep mode. In the sleep mode it wakes up once every 3 seconds to look for activity and to check battery status. If it detects no activity above 10 Lbs., and a battery voltage is above 2.7 Volts then, it goes back to sleep. If the microcontroller detects activity above 10 Lbs. the microcontroller will run in normal operating mode again until another minute of inactivity occurs in which case it will go back into sleep mode. If the battery voltage falls below the 2.7 Volt threshold the power supply will not shut down to protect the power supply to the microcontroller. If the batteries total voltage falls below the 2.7 Volt threshold the microcontroller might not wake up and run properly below 2.5 Volts with out the DC to DC converter running all the time. The circuit will still function properly with the battery voltage below 2.7 Volts, but the power supply will not shut down until the batteries fall below 0.8 Volts. The Hi/Lo battery bit is not changed until the battery voltage falls below 1.6 Volts for reasons of longer operation. Once the batteries reach 1.6 Volts, the battery bit is changed to the Lo setting and during normal activation with a weight of 10 Lbs. or greater, the battery information is sent along in the burst to the receiver for decoding. The transmitter does not transmit unless the user actuates it by stepping on the force plate. The transmitter can be turned off, by removing one or both batteries. The data transfer rate is 9600 baud in each packet or burst. The shoe/transmitter is worn by a patient or individual for periods of minutes up to hours and only transmits the data when the patient or individual steps down on the shoe. When a patient or individual does not wear the shoe the transmitter is rendered inactive and does not transmit data.

123456 A B C D 654321 D C B A Title NumberRevisionSize B Date:18-Sep-1999Sheet of File:C:\FCCCERT\ACCUTX31.SCHDrawn By: SGP Vcc Vcc SGP Vcc Vcc Low Battery Low Battery In RS232 In RS232 Out uController Functions 1. 8-bit analog input 2. RS232 serial port to communicate with computer 3. ID Code input 5-bits 4. Output pulse to turn on power to the Load Cell 5. Low Battery input pin 6. Try to Design around a 3.3 Volt Vcc 7. 50 to 100 words transmitted per second Serial Communication Protocol byte type 1 5-bit ID code + LBI signal 2 8-bit A/D word 3 checksum / error correction 3 pin connector for communication to computer interface for parameter information loading OTR AccuShoe Transmitter, +3.3V Micro Ctrl of Transmitter TX1 3A Rainer G. Riffert 3 of 5 Design Engineers: Rainer G. Riffert & Mike Blair OUT1 1 IN1- 2 IN1+ 3 Vee 4 IN2+ 5 IN2- 6 OUT2 7 Vcc 8 U1 MAX492CSA R4 1.00M R5 1.00M R2 42.2K R3 42.2K R6 42.2K R7 1.00M SHDN 1 3/5 2 REF 3 LBO 4 LBI 5 OUT 6 GND 7 LX 8 U4 MAX856CSA D1 1N5817M L1 47uH + C11 22uF + C12 22uF D2 DL4148 C10 0.1uF C8 0.1uF R14 390K R15 330K MCLR*/Vpp 1 RA0/AN0 2 RA1/AN1 3 RA2/AN2 4 RA3/AN3/Vref 5 RA4/OCKI 6 RA5/AN4/SS* 7 OSC1/CLKIN 9 OSC2/CLKOUT 10 RC0/T1OSO/T1CKI 11 RC1/T1OSI/CCP2 12 RC2/CCP1 13 Vss 8 Vss 19 RC3/SCK/SCL 14 RC4/SDI/SDA 15 RC5/SDO 16 RC6/TX/CK 17 RC7/RX/DT 18 RB0/INT 21 RB1 22 RB2 23 RB3 24 RB4 25 RB5 26 RB6 27 RB7 28 Vdd 20 U2 PIC16LC73A R8 30.1 XTAL1 4.000MHz C4 18pF C3 18pF Q1 BSS84ZX CS 1 CLK 2 DI 3 D0 4 GND 5 NC 6 NC 7 Vcc 8 U3 93C06 DATA IN 1 +Vcc 2 GND 3 RF OUT 4 U5 HX1003 R13 22K C1 0.01uF C14 0.01uF C7 0.01uF C6 0.01uF + C2 10uF Q2 BSS84ZX C9 0.01uF IN2- +3.3V IN2+ GND R1 182K 1 2 3 4 J1 CN4 1 A1 IN2- 1 A3 IN2+ 1 A5 SCREW_HOLE 1 A6 SCREW_HOLE L2 47uH + C13 22uF 1 2 3 4 5 J3 CN5 Vcc Vcc R9 10.0K VccAmp_PWR SG_PWR TRX_PWR + C5 22uF 1 A4 GND R12 100K R10 100K A R11 100K PWR_Shutdown 5V RS232 Input Line 1 5V RS232 Output Line 2 GND 3 J2 RS232-I/O-B Yel Blu Grn Red GND 1 OUTA 2 CS* 3 Din 4 SCLK 5 LDAC* 6 REF 7 Vcc 8 U6 MAX550ACUA Vcc C15 0.01uF C16 220pF TP1 TP-S30 TP2 TP-S30 A2 SGP TP3 TP-S30 TP4 TP-S30 TP5 TP-S30 TP6 TP-S30 TP7 TP-S30 R19 100K Vcc B1 Battery Pack R20 Rx4 R21 100K R22 100K

CD&T FCC ID: OP4ATS-TX418 A. DEVICE UNDER TEST The product is a body worn medical device used to transmit force/weight readings to a companion receiver (OP4ATS-R418). This product is designed to operate under the provisions of Part 15.231(e) of the FCC rules. The transmit frequency is 418 MHz. nominal. The modulation mode is on/off keying. Power for the device is provided by two internal alkaline “AAA” cells. B. MEASUREMENT PROCEDURE: RADIATED EMISSIONS Transmitter field strength measurements were conducted according to the procedures set forth in ANSI C63.4 (1992). Testing was conducted with fresh batteries and monitored periodically to insure that the battery voltage (under load) was maintained at 95% of nominal or better. The device under test was placed on a rotating turntable 0.8 meters high, centered at 3 meters distant from the measurement antenna. The device was placed in the center of the turntable and tested in two positions shown in the test setup photographs. This product is designed to be worn on the foot similar to a shoe and will not transmit unless it is affixed to the foot and downward pressure is applied. A side angle test position (shown in the photograph) was included to insure that there were no hot radiation angles. For the purpose of testing, the micro- controller in the test sample was programmed with a special subroutine to transmit a pulse stream continuously without having to apply pressure to the strain gauge. The field strength measurements were taken using an HP8596E spectrum analyzer, EMCO 3121C dipole set, an EMCO 3115 double ridge guide horn and an Avantek UJ210 preamp. The device was scanned from 30MHz. to 9.2GHz. and all emissions were noted. In this case the only emissions detected were those harmonically related to the fundamental transmit frequency. At each detected frequency of emission, the device was measured by rotating the turntable and adjusting the antenna height over a range of 1 to 4 meters to obtain the maximum output level. This procedure was performed with both horizontal and vertical antenna polarizations with the device in the positions described above. The peak reading for each frequency was recorded in the second column on the data sheet. The measurement for emissions at the 6 th harmonic was performed by reducing the distance from the measurement antenna to 1 meter and factoring –9.54dB into the calculation. No emissions were detected above 2.6 GHz. C. DUTY CYCLE CALCULATIONS The transmission format for this device is RS-232 rendered in a pulse position format. Each data packet consists of 26 bits that represent the device address and the data for the applied pressure reading. The worst case transmission occurs when a force of 256 pounds is applied to the strain gauge transducer. This reading was used for the plots and to calculate the duty cycle correction factor. The data pulses are nominally 92uS. long, but due to rise and fall time errors, some pulse stretching occurs. To allow for this, the pulse and packet measurements were taken at points 12dB. down from peak to insure worst case. The packets are 8.25mS. duration and repeat at 50mS. intervals. The worst case on total time for one packet is 5.35mS. The duty cycle is calculated as follows: 5.35mS. (total on time for 1 packet) X 2 packets (repeat interval)___________ 10.70mS. 20log(10.7mS./100mS.)= -19.4dB The duty cycle correction factor used for the calculations on the data sheet is –19.4dB. As provided in Part 15.35 of the FCC rules.

CD&T FCC ID: OP4ATS-TX418 A. DEVICE UNDER TEST The product is a body worn medical device used to transmit force/weight readings to a companion receiver (OP4ATS-R418). This product is designed to operate under the provisions of Part 15.231(e) of the FCC rules. The transmit frequency is 418 MHz. nominal. The modulation mode is on/off keying. Power for the device is provided by two internal alkaline “AAA” cells. B. MEASUREMENT PROCEDURE: RADIATED EMISSIONS Testing of this device and its associated receiver (OP4ATS-RX418) was conducted at the Hyak Laboratory test facility located in Spotsylvania, Virginia. Transmitter field strength measurements were conducted according to the procedures set forth in ANSI C63.4 (1992). Testing was conducted with fresh batteries and monitored periodically to insure that the battery voltage (under load) was maintained at 95% of nominal or better. The device under test was placed on a rotating turntable 0.8 meters high, centered at 3 meters distant from the measurement antenna. The device was placed in the center of the turntable and tested in two positions shown in the test setup photographs. This product is designed to be worn on the foot similar to a shoe and will not transmit unless it is affixed to the foot and downward pressure is applied. A side angle test position (shown in the photograph) was included to insure that there were no hot radiation angles. For the purpose of testing, the micro- controller in the test sample was programmed with a special subroutine to transmit a pulse stream continuously without having to apply pressure to the strain gauge. The field strength measurements were taken using an HP8596E spectrum analyzer, EMCO 3121C dipole set, an EMCO 3115 double ridge guide horn and an Avantek UJ210 preamp. The device was scanned from 30MHz. to 9.2GHz. and all emissions were noted. In this case the only emissions detected were those harmonically related to the fundamental transmit frequency. At each detected frequency of emission, the device was measured by rotating the turntable and adjusting the antenna height over a range of 1 to 4 meters to obtain the maximum output level. This procedure was performed with both horizontal and vertical antenna polarizations with the device in the positions described above. The peak reading for each frequency was recorded in the second column on the data sheet. The measurement for emissions at the 6 th harmonic was performed by reducing the distance from the measurement antenna to 1 meter and factoring –9.54dB into the calculation. No emissions were detected above 2.6 GHz. C. DUTY CYCLE CALCULATIONS The transmission format for this device is RS-232 rendered in a pulse position format. Each data packet consists of 26 bits that represent the device address and the data for the applied pressure reading. The worst case transmission occurs when a force of 256 pounds is applied to the strain gauge transducer. This reading was used for the plots and to calculate the duty cycle correction factor. The data pulses are nominally 92uS. long, but due to rise and fall time errors, some pulse stretching occurs. To allow for this, the pulse and packet measurements were taken at points 12dB. down from peak to insure worst case. The packets are 8.25mS. duration and repeat at 50mS. intervals. The worst case on total time for one packet is 5.35mS. The duty cycle is calculated as follows: 5.35mS. (total on time for 1 packet) X 2 packets (repeat interval)___________ 10.70mS. 20log(10.7mS./100mS.)= -19.4dB The duty cycle correction factor used for the calculations on the data sheet is –19.4dB. As provided in Part 15.35 of the FCC rules.