DIGILENT PmodACL2 3-Axis MEMS Accelerometer Owner’s Manual
- June 12, 2024
- DIGILENT
Table of Contents
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DIGILENT PmodACL2 3-Axis MEMS Accelerometer
PmodACL2TM Reference Manual
Revised May 24, 2016
This manual applies to the PmodACL2 rev. A 1300 Henley Court Pullman, WA 99163
509.334.6306
Overview
The PmodACL2 is a 3-axis MEMS accelerometer powered by the Analog Devices
ADXL362. By communicating with the chip via the SPI protocol, users may
receive 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.
Product Features
- 3-axis MEMS accelerometer
- Up to 12 bits of resolution per axis
- User-selectable resolution
- Activity/inactivity monitoring
- Low current consumption
Product Usage Instructions
- Connect the PmodACL2 to your microcontroller or development board using the SPI protocol.
- Power on the PmodACL2 and your microcontroller/development board.
- To read the acceleration data, send the appropriate commands to the PmodACL2 via SPI.
- The PmodACL2 provides up to 12 bits of resolution for each axis of acceleration. Use the user-selectable resolution feature to configure the desired resolution.
- To detect external triggers, enable the single or double-tap detection feature on the PmodACL2.
- To save power, utilize the inactivity monitoring feature of the PmodACL2.
- Refer to the PmodACL2 Reference Manual for detailed information on the SPI commands and configuration options.
Overview
The PmodACL2 is a 3-axis MEMS accelerometer powered by the Analog Devices
ADXL362. By communicating with the chip via the SPI protocol, users may
receive 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 though its inactivity
monitoring.
The PmodACL2.
Features include:
-
3-axis MEMS accelerometer
-
Up to 12 bits of resolution per axis
-
User-selectable resolution
-
Activity/inactivity monitoring
-
Low current consumption at <2 μA at 100Hz
-
Free-fall detection
-
Small PCB size for flexible designs 1.0 in ×
0.8 in (2.5 cm × 2.0 cm) -
Follows Digilent Pmod Interface
Specification Type 2A -
Library and example code available
in resource center
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.
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 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 | First Y-axis Address |
---|---|
0 | 0 |
0 | 0 |
LSB Byte of Y-axis Data | MSB Byte of Y-axis Data |
---|---|
b7 | b6 |
SX | SX |
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 FIFO Control Register Address Command FIFO Read
0 0 0 0 1 0 1 0 0 0 1 1 0 0 0 0 0 0 0 0 1 1 0 1
LSB Byte of Axis Data | MSB Byte of Axis Data |
---|---|
b7 | b6 |
b15 | b14 |
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.
Pinout Description Table
Pinout Table of the PmodACL2
Connector J1| | Connector J2|
Pin| Signal| Description| | Pin| Signal|
Description| Pin| Signal| Description|
1| ~CS| Chip select| 7| INT2| Interrupt Two| 1| INT1| Interrupt One|
2| MOSI| Master Out Slave
In
| 8| INT1| Interrupt One| 2| G| Power Supply
Ground
|
3| MISO| Master In Slave
Out
| 9| NC| Not connected| Connector J3|
4| SCLK| Serial clock| 10| NC| Not connected| Pin| Signal|
Description|
5| GND| Power supply
ground
| 11| GND| Power supply
ground
| 1| INT2| Interrupt Two|
6| VCC| Power supply
(3.3V)
| 12| VCC| Power supply
(3.3V)
| 2| G| Power Supply
Ground
|
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.
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.
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