ADXL345 3‐axis MEMS accelerometer
The ADXL345 is a small, thin, low power, 3-axis MEMS accelerometer with high resolution (13-bit) measurement at up to +/-16 g. Digital output data is formatted as 16-bit two's complement and is accessible through either an SPI (3- or 4-wire) or I2C digital interface.
The single and double tap sensing detects when a single, or two simultaneous, acceleration events occur. Activity and inactivity sensing detect the presence or lack of motion. Free-fall sensing compares the acceleration on all axes with the threshold value to know if the device is falling. All thresholds levels that trigger the activity, free-fall, and single tap/double tap events are user-set levels. These functions can also be mapped to one of two interrupt output pins. An integrated, patent pending 32-level first in, first out (FIFO) buffer can be used to store data to minimize host processor intervention.
| Mnemonic | Description |
|---|---|
| GND | This pin must be connected to ground |
| VCC | Supply Voltage |
| CS | Chip Select |
| INT1 | Interrupt 1 Output |
| INT2 | Interrupt 2 Output |
| SDO | Serial Data Output (SPI 4-Wire) / I2C Address Select |
| SDA / SDI / SDIO | Serial Data I2C / Serial Data Input (SPI 4-Wire) / Serial Data Input and Output (SPI 3-Wire) |
| SCL / SCLK | Serial Communications Clock |
In SPI mode, the CS pin is controlled by the bus master. For SPI, either 3- or 4- wire configuration is possible.
Note: When using 3-wire SPI, it is recommended that the SDO pin be pulled up to VDD I/O or pulled down to GND via a 10 kΩ resistor. Please refer to page 15 of the ADXL345 Datasheet for additional information.
The following is a table describing which pins on the Arduino should be connected to the pins on the accelerometer for SPI 4-wire communication.
| Arduino Pin | ADXL345 Pin |
|---|---|
| GND | GND |
| 3V3 | VCC |
| 10 | CS |
| 12 | SDO |
| 11 | SDA |
| 13 | SCL |
Supports 5V/3.3V voltage input, on-board RT9161 power chip, lower pressure drop faster than the 1117, faster load speed of response, very suitable for high-noise power supply environment.
| Pin Name | Type | Function | Notes |
|---|---|---|---|
| GND | Power | Ground | Connects to the Ground pin of your microcontroller (e.g., Arduino/Raspberry Pi). |
| Vs (or VIN) | Power | Input Supply Voltage | This is the main power input. Connect this to 3v3 on your microcontroller. This appears to be connected to the 3V3 pin |
| 3V3 | Power | 3.3V Output/Input | Output: Regulated 3.3V from the onboard regulator (can power small 3.3V components). Input: If your microcontroller runs at 3.3V, you can often power the board directly here instead of Vs. |
| 5V | Power | 5V Input (Sometimes) | Sometimes labeled instead of Vs as the primary 5V input, or used as the input to the level shifter. Treat as the main VCC input for a 5V system. |
| CS | Control | Chip Select (SPI Mode) / Mode Select (I²C) | SPI: Driven LOW to enable communication. I²C: Typically tied HIGH (often to 3V3) to select I²C mode. |
| SCL | Digital I/O | Serial Clock (I²C) / SCK (SPI Clock) | Connects to the SCL/SCK pin on your microcontroller. |
| SDA | Digital I/O | Serial Data (I²C) / MOSI (SPI Data Input) | Connects to the SDA/MOSI pin on your microcontroller. |
| SDO | Digital I/O | Serial Data Output (SPI MISO) / I²C Alternate Addr | SPI: Data output to the controller. I²C: Selects the I²C address; tying to GND or 3V3 changes the last address bit (commonly 0x53 ↔ 0x1D). |
| IN1 | Interrupt | Interrupt Output 1 | Configurable interrupt pin for motion events (e.g., free-fall, activity/inactivity, tap detection). |
| IN2 | Interrupt | Interrupt Output 2 | Second configurable interrupt output pin. |
- Supply Voltage: 2.0 - 3.6 VDC
- Ultra Low Power: As low as 23 uA in measurement mode, 0.1uA in standby mode at 2.5V
- SPI or I2C Communication
- Single Tap / Double Tap Detection
- Activity / Inactivity Sensing
- Free-Fall Detection