UG-065 Datasheet, PDF (3/12 Pages) Analog Devices – Battery-powered for portable applications

Evaluation Board User Guide
UG-065
OVERVIEW
The ADXL345/ADXL346 inertial sensor development board
has the following features:
• A 2-layer printed circuit board (PCB), 1.20 inches ×
2.30 inches form factor
• A two AAA battery power supply
• A 4-pin UART header to connect to an RS-232 interface
cable
• Reset/download push buttons
• Power indicator/general-purpose LEDs
• Access to microcontroller I/Os from the external header
• Demonstration firmware logs 100 Hz acceleration data
FEATURES
Power Supply
A pair of AAA batteries powers the board, and the battery holder is
located on the back of the board. An on/off switch on the lower
left of the front of the board controls power to it. The battery
voltage is not regulated but is decoupled with a 10 μF capacitor
globally and an additional 1 μF capacitor at the device supply
pins to ground.
RS-232 Interface
The ADuC7024 (UC1) P1.1 and P1.0 lines are connected to the
RS-232 interface cable via the connector (UART). The interface
cable generates the required level shifting to allow direct connection
to a PC serial port. Ensure that the supplied cable is connected
to the board correctly; that is, VDD is connected to VDD and
GND is connected to GND.
RESET/PROG Push Buttons
A RESET push button is provided to allow the user to manually
reset the part. When the RESET button is inserted, the RST pin
of the ADuC7024 is pulled to GND. Because the RST pin is
Schmitt-triggered internally, there is no need to use an external
Schmitt trigger on this pin.
To enter serial download mode, the user must hold the P0.0/BM
pin low while reset is toggled. On the development board, serial
download mode can be easily initiated by holding down the serial
download push button (PROG) while inserting and releasing
the reset button (RESET), as illustrated in Figure 2.
Power Indicator/General-Purpose LEDs
Two general-purpose LEDs are available on the board. A red
LED (LED1) is connected to P4.5 of the ADuC7024, and a green
LED (LED2) is connected to P4.4. Both LEDs can be repurposed
via firmware.
Breakout Header
Many of the ADuC7024 pins are connected to headers on either
side of the board. The headers come unpopulated but can be
populated using standard 0.1 inch header pins.
The thin form factor of the top of the board allows the design
of an expansion board to connect above the development board,
with the header pins providing both electrical and physical
connections.
Firmware
Sample firmware is provided on the ADXL345 product page
under the Development Board heading. The Firmware
link downloads a Keil project that implements the 100 Hz
datalogging firmware. This project can be modified as needed.
(A) RESET AND PROG RELEASED
(B) PUSH PROG
(C) PUSH RESET
RESET
PROG
RESET
(D) RELEASE RESET
PROG
RESET
(E) RELEASE PROG
PROG
RESET
PROG
RESET
PROG
Figure 2. Entering Serial Download Mode to Reprogram the Board
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