Freescale's ZSTAR3 wireless sensor reference design offers a flexible solution for both analog and digital accelerometers, enabling communication with a PC via a USB node using the RF ZigBee® 2.4 GHz module. The ZSTAR3 system includes key components such as the three-axis analog accelerometer MMA7361L, the three-axis digital accelerometer MMA745xL, and the System-in-Package (SiP) MC13213. This article provides an in-depth overview of the main features of these components, along with the sensor board block diagram, material list, and circuit diagram for both analog and digital sensor configurations.
The ZSTAR3 design supports multiple wireless sensing boards equipped with either analog or digital accelerometers. These boards connect wirelessly through ZigBee to a single USB node that links to a PC. Each board measures acceleration across three axes using a pin-compatible digital sensor or an optional analog sensor. The sensitivity is determined by the selected accelerometer, making it adaptable for various applications.
The ZSTAR3 project comes with a new PC software interface that allows users to access basic accelerometer functions and explore different use cases. Freescale’s RD3172MMA7456L ZSTAR3 reference design simplifies wireless control and streamlines development. It is a compact, portable board that integrates the following key components:
- MMA7361L analog or MMA7456L digital triple-axis accelerometer
- MC1321x 2.4 GHz low-power transceiver combined with an S08 MCU in one package
Target applications include mobile phones, handheld gaming devices, portable media players, MP3 players, PDAs, computer peripherals, GPS navigation systems, healthcare devices, toys, and robotics. The ZSTAR3 is ideal for demonstrating and evaluating cost-effective, low-power wireless solutions.
Figure 1: ZSTAR3 Reference Design Outline Drawing
The ZSTAR3 reference design supports the following main components:
1) **Three-Axis Analog Accelerometer MMA7361L**
The MMA7361L is a low-power, low-profile capacitive micromachined accelerometer featuring signal conditioning, a 1-pole low-pass filter, temperature compensation, self-test, 0g-detect for free-fall detection, and g-Select for selecting between two sensitivities. It operates on a wide voltage range and includes a sleep mode for battery-powered devices.
Main Features:
- 3mm x 5mm x 1.0mm LGA-14-pin package
- Low current consumption: 400 μA
- Sleep mode: 3 μA
- Operating voltage: 2.2 V – 3.6 V
- High sensitivity: 800 mV/g at 1.5g
- Fast startup: 0.5 ms enable response time
- Self-test and 0g-detect for free-fall protection
- Signal conditioning with low-pass filter
- Robust design, high shock survivability
- RoHS compliant and environmentally preferred
2) **Three-Axis Digital Accelerometer MMA745xL**
The MMA745xL is a digital-output (I2C/SPI), low-power, 3x5x1 mm capacitive micromachined accelerometer with signal conditioning, a low-pass filter, temperature compensation, self-test, and interrupt-based 0g detection. It also supports pulse (click) detection for motion recognition and offers programmable thresholds for motion tracking.
Main Features:
- Digital output (I2C/SPI)
- Low-profile 14-pin 3mm x 5mm x 1mm LGA package
- XYZ sensitivity in one device (2g/4g/8g)
- Standby mode: 5 μA
- Low-voltage operation: 2.4 V – 3.6 V
- Customer-calibrated offset registers
- Programmable threshold interrupts
- Motion detection (shock, vibration, free-fall)
- Click (pulse) recognition
- High sensitivity: 64 LSB/g at 2g and 8g in 10-bit mode
3) **System-in-Package (SiP) MC13213**
The MC13213 SiP combines the MC9S08GT MCU with the MC1320x transceiver into a single 9x9mm LGA package. It supports IEEE 802.15.4 compliant MAC or BeeStack ZigBee protocol stacks, making it suitable for mesh networking applications.
Main Features:
- 40 MHz HCS08 core
- 60 KB Flash and 4 KB RAM
- 7 CPU addressing modes
- Multiple 16-bit timers
- 2V–3.4V operating voltage with on-chip regulator
- -40°C to +85°C operating temperature
- Low external component count
- Single 16 MHz crystal required
- Auto-trim for crystal accuracy
- 9x9x1 mm 71-pin LGA package
Figure 2: Sensor Board Block Diagram
Table 1: Sensor Board Bill of Materials (Using Analog Sensors)
Table 2: Sensor Board Bill of Materials (Using Digital Sensors)
Figure 3: ZSTAR3 Circuit Diagram
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