Digilent 410-097P User Manual

PPmmooddAACCLL™™ RReeffeerreennccee MMaannuuaal

Revision: August 30, 2011
Note: This document applies to REV E of the board.

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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 I2C interfaces

Functional Description

The PmodACL uses a standard 12-pin
connector and can communicate via SPI or
I2C. A pull-up resistor on the ~SS line keeps
the ADXL345 in I2C 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.

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Interface Connector Signal Description

Connector J1 – SPI Communications
Pin Signal Description

1 ~SS Slave Select
2 MOSI / SDA SPI Master out Slave

in Data / I2C 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)

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
MOSI corresponds to Serial Data Input (SDI),
MISO corresponds to Serial Data Output
(SDO), and SCK corresponds to the Serial
Clock signal (SCLK).

(~CS),

PmodACL Reference Manual

Connector J2 – I2C Communications
Pin Signal Description

1, 2 SCLK Serial Clock

3, 4 SDA / SDI /

SDIO

I2C Data / SPI Master

out Slave in Data
5, 6 GND Power Supply Ground
7, 8 VCC Power Supply (3.3V)

The I2C interface standard uses two signal
lines. These are I2C data (SDA) and serial
clock (SCLK). These signals map to the serial
data (SDA) and serial clock (SCLK)
respectively on the ADXL345.

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Copyright Digilent, Inc. All rights reserved. Other product and company names mentioned may be trademarks of their respective owners.