Revision as of 00:18, 14 September 2007

State Machine (Master) Controller

• 25.38V max supply voltage (6 cell LiPoly)
• IIC EEPROM for controller parameters (24LCxx)

Off board interfaces

Switch Input

• external logic switch input for mode control

External Serial Communication and ISP

• Ability to support a variety of attached serial devices: wired RS-232, Bluetooth, 802.11, and ISP.
• 1Mbaud (max) RS-232 level ASYNC serial (Tx, Rx, RTS, CTS) :
• Power for external devices: 5V and Vbat (with 0.25amp self resettable fuse)
• ISP signals (PGC, PGD, MCLR) for external ISP
• signals: Vbat, Vcc5, GND, Tx, Rx, RTS, CTS, PGC, PGD, MCLR

Power / Data to Motor Controller

• logic level ASYNC 2-wire serial between SM and motor controller CPUs
• logic level output to motor controller fault pin to disable PWM
• logic level input for motor controller alert status
• (Vbat) battery power from motor controller
• sense path to battery for voltage monitoring
•  ??? board to board stacking connector (more reliable that wires)

Ankle Angle Sensor

Strain, SEA, Motor Temp, Supply current, Ankle Ankle

• 5 analog inputs to CPU, DC to 500 Hz analog bandwidth
• 1 x 10k(or more) thermo resistor (requires opamp follower) : AGND and signal
• 2 x strain gauge bridges (340 or 1k ohm) to high gain INA326 : AGND, SG+, SG-, bridge reference
• SG bridge reference voltage through 0.1% resistance (1k to reduce bridge current) ideally from AVCC3.3 (ADC reference) or from AVCC5
• 1 x analog input for SEA hall sensor board (no voltage or current amp required) : 3.3V, AGND, signal
• 1 x analog input for ankle angle (10k-100k) potentiometer (higher bandwidth for fast power cycling)

Vibrator Motor and Piezo

• 4 pin header
• ability to turn on/off pager motor (3.3V)
• ability to drive miniature piezo (from PWM or OC)

On board sensors

Ambient Temperature

• Thermo resistor (>=10k) with opamp follower placed very close to XY axis IMU

Supply Voltage Monitor

• (better than) 1% accurate measurement of battery voltage (prevent over-voltage during regeneration)

IMU

• One SPI device, and (upto) 3 analog rate gyro signals

• 3axis (SPI) accelerometer LIS3LV02DQ
• Z axis rate gyro ADXRS300 (analog) or ADIS16100 (digital)
• XY axis (analog) rate gyro IDG300
• Note: XY is in circuit board plane, Z axis is normal to circuit board plane

AVCC5 monitor

• If SG bridge is powered from AVCC5 then we need to measure AVCC5/2, and SG bridge offsets depend on AVCC5

LEDs

• 2 LEDs mounted so as to be externally visible

Low Power Support

• Design for overall low power
• Target for sleep power of 5mW (0.12WHr/day - from VBAT), processor is sleeping.
• RS232 output interface disable (Rx still active - SN75C3223)
• Control of supply to internal sensors : ambient temperature, IMUs
• Control of supply to external sensors : ankle angle, SG, SEA, motor temperature

Sensor Power

• EC30 MR-ENC 15.5mA @ 5V 77.5mW
• EC30 HALL SEN 10.6mA @ 5V 53mW

• IDG300 9.5mA @ 3.3V 31.mW
• ADXRS300 6-8mA @ 5V 35mW
• ADIS16100 7-9mA @ 5V 40mW

• ADIS16006 1.5-1.9 @ 3-5V 5 mW
• LIS3LV02DQ .6-.8 @ 2.2-3.3V < 2.6mW
• ankle angle pot 0.1-1mW

software

• ability to reprogram controller over ASYNC serial
• 2 DMA controllers run the two ADC units at 12 bits, 400 KHz total sample rate
• Input capture measures PWM period of magnetic rotary encoder / QEI captures encoder position
• DMA controller sends/receives SPI to digital accelerometer
• Main code loop runs at 500 Hz
  • decimation of analog inputs
  • reads ankle position
  • reads IMU, estimates orientation
  • reads motor controller status (motor current, motor position, status)
  • processes external communication interface

Motor Controller

Motor