1300 Henley Court Pullman, WA 99163 509.334.6306 www.digilentinc.com PmodACL2TM Reference Manual Revised February 2, 2015 This manual applies to the PmodACL2 rev. A Overview The Digilent PmodACL2 is a 3-axis micro electro-mechanical systems (MEMS) accelerometer that can provide up to 12 bits of resolution for each axis of acceleration. Additionally, this module offers external trigger sensing through single or double-tap detection as well as power saving features through its inactivity monitoring. Features include: User-selectable resolution. Less than 2 A consumption at 100 Hz. Single or double-tap detection. Activity and inactivity monitoring. Free fall detection. The PmodACL2. 1 Functional Description The PmodACL2 utilizes Analog Devices ADXL362 to provide MEMS acceleration data to the system board. With its deep 512-sample FIFO buffer, users are able to view a long string of events prior to a triggered interrupt or simply be able to have the system board access acceleration data when the user finds it most convenient. 2 Interfacing with the Pmod The PmodACL2 communicates with the host board via the SPI protocol. To read from the on-board data registers, the Chip Select line must first be pulled low and then send a command byte to read from the data registers (0x0B). The desired address byte must be sent next, and then the desired byte is received with the MSB first on the falling DOC#: 502-255 Copyright Digilent, Inc. All rights reserved. Other product and company names mentioned may be trademarks of their respective owners. Page 1 of 3 PmodACL2TM Reference Manual clock edge. Because the address pointer auto-increments to the next address byte, it is possible to read multiple bytes consecutively by continuing to pulse the Serial Clock line. An example set of commands to read from the yaxis register is given below: Command Read 0 0 First Y-axis Address 0 0 1 0 1 1 0 LSB Byte of Y-axis Data b7 b6 b5 b4 0 0 0 1 0 1 0 MSB Byte of Y-axis Data b3 b2 b1 LSB SX SX SX SX MSB b10 b9 b8 Note: Each SX bit is the same value as the most significant bit of the y-axis data. To read from the FIFO buffer, a command byte to write to a data register (0x0A) must first be sent so that we can configure the FIFO Control register (address 0x28) to indicate that we want the FIFO buffer to store data. After the ADXL362 has been configured to use the FIFO buffer, a command byte to read from the FIFO buffer (0x0D) must first be sent, then followed by pairs of data bytes containing which axis is being measured as well as the acceleration data. An example set of commands to read from the FIFO buffer is given below: Command Read 0 0 0 FIFO Control Register Address 0 1 0 1 0 0 0 1 LSB Byte of Axis Data b7 b6 b5 b4 1 0 0 Command FIFO Read 0 0 0 0 0 0 1 1 b10 b9 b8 0 1 MSB Byte of Axis Data b3 b2 b1 LSB b15 b14 SX SX MSB Note: Each SX bit is the same value as the most significant bit of the y-axis data. b15 and b14 represent which axis the incoming data represents. 2.1 Pinout Description Table Pin 1 Signal ~CS 2 MOSI 3 MISO 4 SCLK 5 GND 6 VCC Pinout Table of the PmodACL2 Connector J1 Description Pin Signal Description Chip select 7 INT2 Interrupt Two Master Out Slave 8 INT1 Interrupt One In Master In Slave 9 NC Not connected Out Serial clock 10 NC Not connected Power supply Power supply 11 GND ground ground Power supply Power supply 12 VCC (3.3V) (3.3V) Copyright Digilent, Inc. All rights reserved. Other product and company names mentioned may be trademarks of their respective owners. Pin 1 2 Connector J2 Signal Description INT1 Interrupt One Power Supply G Ground Connector J3 Pin Signal Description 1 INT2 Interrupt Two 2 G Power Supply Ground Page 2 of 3 PmodACL2TM Reference Manual The PmodACL2 also has two programmable interrupt pins available for use. Both of these pins can be set to trigger an interrupt upon multiple different triggers including activity/inactivity (to help reduce system power), when the FIFO buffer is filled to a desired level, when data is ready to be retrieved, and other triggers. Any external power applied to the PmodACL2 must be within 1.6V and 3.5V. Consequently, with Digilent system boards, this Pmod must be run off of a 3.3V rail. 3 Physical Dimensions The pins on the pin header are spaced 100 mil apart. The PCB is 0.95 inches long on the sides parallel to the pins on the pin header and 0.8 inches long on the sides perpendicular to the pin header. Copyright Digilent, Inc. All rights reserved. Other product and company names mentioned may be trademarks of their respective owners. Page 3 of 3