User Manual
Table Of Contents
- Revision History
- Table of Contents
- Chapter 1 Introduction
- Chapter 2 Wireless Sensing Triple Axis Reference design introduction
- Chapter 3 Sensor Board description
- 3.1 Board overview
- 3.2 A/D conversion of XYZ levels
- 3.3 Power management
- 3.4 ZSTAR Sensor Board hardware overview
- 3.4.1 Analog connections
- 3.4.2 g-select connections
- 3.4.3 BDM (Background Debug Mode) connections
- 3.4.4 Sensor Board schematics
- 3.4.5 Button connections
- 3.4.6 MC13191 to MC9S08QG8 microcontroller interface
- 3.4.7 MC13191 RF interface
- 3.4.8 Clocking options of MC9S08QG8
- 3.4.9 LED indicators connections
- 3.4.10 Power supply
- 3.5 Bill of Materials
- Chapter 4 USB stick board description
- Chapter 5 Software Design
- 5.1 Introduction
- 5.2 SMAC (Simple Media Access Controller)
- 5.3 ZSTAR RF protocol
- 5.4 STAR protocol and ZSTAR extensions (over USB)
- 5.5 Bootloader
- Chapter 6 Application Setup
- Appendix A References
USB stick board description
Wireless Sensing Triple Axis Reference design, Rev. 0.9
30 Freescale Semiconductor
4.2 ZSTAR USB stick Board hardware overview
This section describes the USB stick board in terms of the hardware design. The MCHC908JW32
microcontroller drives the MC13191 RF transceiver and communicates over USB with PC.
4.2.1 USB connections
Two USB communication lines are connected directly via R1 to PTE2/D+ and R2 to PTE3/D-
microcontroller pins. There, the R1 and R2 resistors define the output impedance of both drivers (Z
DRV
as per chapter 7 of the USB 2.0 specifications).
Terminating the D+ line with a 1.5kΩ pull-up resistor (required for Full-speed signalling) is internal in the
MCHC908JW32.
A USB “A” type SMT Plug is designed at the edge of the USB stick board allowing the stick to be
connected directly into a USB hub without the need for a cable.
4.2.2 Power supply
The USB stick board is a Low-power Bus-powered Function (as defined in chapter 7.2.1.3 of USB 2.0
specifications). This means that a maximum of one unit load (100mA) may be drawn by the USB Stick
board. Ferrite beads are included on the VBUS and GND USB connections to minimize EMI. The
recommended type is a GLF1608T100M or similar from TDK.
V
BUS
voltage is defined as a minimum 4.4V and a maximum 5.25V on a Low-power Bus-powered
Function.
The MC13191 RF transceiver requires a maximum power supply voltage of 3.4V and the MCHC908JW32
microcontroller could not guarantee an internal 3.3V regulator working at such a low power supply.
Therefore, two separate voltage regulators need to be implemented, and in addition, the voltage levels
have to be close enough to avoid the need for level shifters (for the MC13191 to MCHC908JW32
microcontroller interface).
4.2.2.1 Fixed voltage regulators
Two voltage levels (3.3V for MC13191 and 3.6V for MCHC908JW32) were selected. For these levels, a
low-cost, small footprint fixed regulator exists. The NCP502/A series regulators from ON
Semiconductor
TM
were successfully implemented.
The NCP502/A series voltage regulator is an 80mA CMOS fixed linear regulator designed primarily for
handheld communication equipment and portable battery powered applications which require a low
quiescent current.
Each device contains a voltage reference unit, an error amplifier, a PMOS power transistor, resistors for
setting the output voltage, current limit, and temperature limit protection circuits. The NCP502/A has been
designed to be used with low cost ceramic capacitors. The device is housed in a micro-miniature SC70-5
surface mount package. Standard voltage versions are 1.5 V, 1.8 V, 2.5 V, 2.7 V, 2.8 V, 3.0 V, 3.3 V, 3.5
V, 3.6 V and 5.0 V. Other voltages are available in 100 mV steps.
Typically, a low-cost 1µF ceramic capacitor is recommended for input and output decoupling. 0603-sized
SMD TDK capacitor C1608X5R1A105K was used.