Figure 3-11. Gps/Bluetooth/Accelerometer Block Diagram - Motorola APX 3000 Basic Service Manual

Basic Theory of Operation: Controller Section
Misc Control // 7
128MB
SDRAM
Accelero-
meter
3.4.1 Radio with Mace
In addition to the Mace features, the Main Board consists of a 3-axes digital accelerometer and the
Bluetooth Controller IC (AVR) together with LF Wakeup IC (AS3930A) for Secure Pairing.
The radio also has the ability to connect to a wireless Bluetooth audio headset. This feature is
implemented using a combination Bluetooth/GPS integrated circuit (NL5500 IC) located on the Main
board. An optional accessory headset can connect using a low-data rate GFSK modulated signal
hopping on 79 x 1 MHz wide Bluetooth channels from 2402 MHz to 2480 MHz in the ISM band. Each
APX accessory that is capable of Bluetooth communication will have its own unique Bluetooth
address. Bluetooth uses a frequency hopping spread spectrum (FHSS) technique to spread the RF
power across the spectrum to reduce the interference and spectral power density. The frequency
hopping allows the channel to change up to 1600 times a second (625 μs time slot) based on a
pseudo random sequence. If a packet is not received on one channel, the packet will be
retransmitted on another channel. The Bluetooth IC sends data to the AVR32 processor over an HCI
UART link. The AVR32 processor communicates to the OMAP processor on the main board through
a dedicated USB port.
The Bluetooth feature is accompanied by a Low-Frequency (LF) detection circuit. The LF circuit
provides the ability of a secure pairing connection with a Bluetooth accessory. Once a radio has the
Bluetooth feature enabled, a user can tap their LF enabled Bluetooth audio accessory with the radio
at the pairing spot to establish a secure Bluetooth connection. The LF circuit uses a 125 kHz
radiated signal to communicate the secure pairing information between the Bluetooth accessory and
low-frequency receiver. The low-frequency receiver is programmed by the AVR32 processor through
a dedicated SPI bus and transfers the pairing data through a dedicated UART.
There is a digital accelerometer on the main board that detects the 3-axis force of gravity which can
be used to determine the radio's orientation. The accelerometer's position is communicated to the
AVR32 processor through a SPI bus.
OMAP 1710
USB // 2
// 38
ATMEL AVR32
AT32UC3A0512
64kB SRAM
512kB Flash
// 6
12MHz
LF IC
XTAL

Figure 3-11. GPS/Bluetooth/Accelerometer Block Diagram

Main Board
GPS_Shutdown // 1
UART (GPS Tx/Rx) // 2
SSI (BT Audio) // 4
UART (BT HCI) // 4
GPS+Bluetooth
Combo Chipset
BT Control // 3 NL5500
// 1
// 1
32kHz
from CPLD
LF Antenna (located on flex)
GPS/RF Antenna
GPS SAW
GPS/RF
filters &
Diplexer
LNA
BT Antenna
BT
Filter
// 1
26MHz
TCXO
3-9