====== Pmod ACL Reference Manual ======

The Digilent Pmod ACL (Rev. E) is a 3-axis digital accelerometer module powered by the [[http://www.analog.com/static/imported-files/data_sheets/ADXL345.pdf|Analog Devices ADXL345]]. 

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== Download This Reference Manual == 
  * {{:reference:pmod:pmodacl:pmodacl_rm.pdf| PDF}}

===== Features =====
  * 3-axis, ±2/4/8/16g accelerometer
  * User-selectable resolution 
  * Activity/inactivity monitoring  
  * Single/double-tap and free-fall detection 
  * Small PCB size for flexible designs 1.0 in × 0.8 in (2.5 cm × 2.0 cm) 
  * 12-pin Pmod port with SPI interface and 2×4-pin I²C interface
  * Follows Digilent Pmod Interface Specification Type 2A
  * Library and example code available in resource center

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=====Functional Description =====
The %%Pmod ACL%% utilizes [[http://www.analog.com/static/imported-files/data_sheets/ADXL345.pdf|Analog Devices ADXL345]] to provide high resolution acceleration changes including inclination changes of less than 1.0°. With free fall and single/double tap detection capabilities, the %%Pmod ACL%% can be configured to take measurements on the user's whim.

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===== Interfacing with the Pmod=====
The %%Pmod ACL%% communicates with the host board via the [[pmod:communication_protocols:spi|SPI protocol]] or the [[pmod:communication_protocols:i2c|I²C protocol]]. SPI communication is enabled when the Chip Select line is driven low; conversely, the I²C protocol is enabled when the Chip Select line is driven to a logic level high voltage. An interrupt can be triggered whenever a measured axis acceleration data is over a user defined threshold limit. A data stream setting the threshold activity to a value of 250 mg and Interrupt 1 to be triggered whenever the X and Y axis exceeds the threshold level through SPI is provided below:


^  Read/~Write  ^  Multi-byte  ^  6-bit Threshold Activity Address  ||||||
|  0  |  0  |  1  |  0  |  0  |  1  |  0  |  0  |
^  8 bits of Threshold Activity data (62.5 mg/LSB scale)  ||||||||
|  0  |  0  |  0  |  0  |  0  |  1  |  0  |  0  |
^  Read/~Write  ^  Multi-byte  ^  6-bit Activity/Inactivity Control Address  ||||||  
|  0  |  0  |  1  |  0  |  0  |  1  |  1  |  1  |
^  Activity/Inactivity Control Settings  ||||||||
|  ACT ac/dc  |  ACT X  |  ACT Y  |  ACT Z  |  INACT ac/dc  |  INACT X  |  INACT Y  |  INACT  Z  |
|  0  |  1  |  1  |  0  |  0  |  0  |  0  |  0  |
^  Read/~Write  ^  Multi-byte  ^  6-bit Interrupt Enable Address  ||||||  
|  0  |  0  |  1  |  0  |  1  |  1  |  1  |  0  |
^  8 bits of Which Interrupt Sources Are Enabled  ||||||||
|  Data Ready  |  Single Tap  |  Double Tap  |  Activity  |  Inactivity  |  Free Fall  |  Watermark  |  Overrun  |
|  0  |  0  |  0  |  1  |  0  |  0  |  0  |  0  |

Once an interrupt has been generated, users may read the data registers (0x32 - 0x37) for the 10 bits of [[:twos_complement|two's complement data]] in the X, Y, and Z axes, respectively. The data in the two registers for each axis is right justified with sign extensions as the leading 6 bits. Reading the Interrupt source register (0x30) clears the activity interrupt bit D4. 

Users may also follow the given [[pmod:pmodacl:start#example_projects|example code]] functions and demonstration to start collecting accelerometer data. 


==== Pinout Description Table ====
^  Pmod Header J1                                               |||||||   ^  Pmod Header J2  |||
^ Pin ^  Signal  ^  Description  | ^ Pin  ^  Signal  ^  Description  |:::^ Pin ^  Signal  ^  Description  |
|  1  |  ~CS   |  Chip Select  |:::|  7   |  INT2  |  Interrupt 2  |:::|  1, 5  |  SCL  |  Serial Clock  |
|  2  |  MOSI  |  Master-Out-Slave-In  |:::|  8   |  INT1  |  Interrupt 1  |:::|  2, 6  |  SDA  |  Serial Data  |
|  3  |  MISO  |  Master-In-Slave-Out  |:::|  9  |  NC  |  Not Connected  |:::|  3, 7  |  GND  |  Power Supply Ground  |
|  4  |  SCK  |  Serial Clock  |:::|  10  |  NC  |  Not Connected  |:::|  4, 8  |  VCC  |  Positive Power Supply  |
|  5  |  GND   |  Power Supply Ground  |:::|  11  |  GND   |  Power Supply Ground  |:::| |||
|  6  |  VCC   |  Power Supply (3.3V)  |:::|  12  |  VCC   |  Power Supply (3.3V)  |:::|:::|||

Any external power applied to the %%Pmod ACL%% must be within 2.0V and 3.6V; it is strongly recommended that Pmod is operated at 3.3V.
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===== Physical Dimensions =====
The pins on the pin header are spaced 100 mil apart. The PCB is 1 inch 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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===== Additional Information =====
The schematics of the %%Pmod ACL%% are available {{reference:pmod:pmodacl:pmodacl_sch.pdf|here}}. Additional information about the accelerometer including communication modes and specific timings of the chip can be found by checking out its datasheet [[http://www.analog.com/media/en/technical-documentation/data-sheets/ADXL345.pdf|here]]. 

Example code demonstrating how to get information from the %%Pmod ACL%% can be found [[pmod:pmodacl:start#example_projects|here]].

If you have any questions or comments about the %%Pmod ACL%%, feel free to post them under the appropriate section ("Add-on Boards") of the [[https://forum.digilentinc.com/|Digilent Forum]].