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Revision: August 30, 2011
Note: This document applies to REV E of the board.
1300 NE Henley Court, Suite 3
Pullman, WA 99163
(509) 334 6306 Voice | (509) 334 6300 Fax
Doc: 502-097 page 1 of 2
Copyright Digilent, Inc. All rights reserved. Other product and company names mentioned may be trademarks of their respective owners.
Overview
The PmodACL is a 3-axis digital accelerometer
module powered by the Analog Devices
ADXL345.
Features include:
• user-selectable resolution
• single-tap/double-tap detection
• activity/inactivity monitoring
• free fall detection
• SPI and I
2
C interfaces
Functional Description
The PmodACL uses a standard 12-pin
connector and can communicate via SPI or
I
2
C. A pull-up resistor on the ~SS line keeps
the ADXL345 in I
2
C mode unless the host
drives the line low, in which case the device
will communicate via SPI.
Interface
All communications with the device must
specify a register address and a flag indicating
whether the communication is a read or a
write. This is followed by the actual data
transfer.
Device configuration is performed by writing to
control registers within the device.
Accelerometer data is accessed by reading
device registers.
A full list of registers and their functionality, as
well as communication specifications, is found
in the ADXL345 datasheet available on the
Analog Devices website.
The SPI interface standard uses four signal
lines. These are slave select (~SS), master out
slave in (MOSI), master in slave out (MISO),
and serial clock (SCLK). These signals map to
the following signals on the ADXL345: ~SS
corresponds to the Chip Select signal (~CS),
MOSI corresponds to Serial Data Input (SDI),
MISO corresponds to Serial Data Output
(SDO), and SCK corresponds to the Serial
Clock signal (SCLK).
Connector J1 – SPI Communications
Pin Signal Description
1 ~SS Slave Select
2 MOSI / SDA SPI Master out Slave
in Data / I
2
C Data
3 MISO SPI Master in/Slave
out Data
4 SCLK Serial Clock
5 GND Power Supply Ground
6 VCC Power Supply (3.3V)
7 INT2 Interrupt 2
8 INT1 Interrupt 1
9 NC Not Connected
10 NC Not Connected
11 GND Power Supply Ground
12 VCC Power Supply (3.3V)
Interface Connector Signal Description
PmodACL Reference Manual
www.digilentinc.com page 2 of 2
Copyright Digilent, Inc. All rights reserved. Other product and company names mentioned may be trademarks of their respective owners.
The I
2
C interface standard uses two signal
lines. These are I
2
C data (SDA) and serial
clock (SCLK). These signals map to the serial
data (SDA) and serial clock (SCLK)
respectively on the ADXL345.
Connector J2 – I
2
C Communications
Pin Signal Description
1, 2 SCLK Serial Clock
3, 4 SDA / SDI /
SDIO
I
2
C Data / SPI Master
out Slave in Data
5, 6 GND Power Supply Ground
7, 8 VCC Power Supply (3.3V)
