The little chip in the middle of the PCB is the actual MMA8451 sensor
that does all the motion sensing. We add all the extra
components you need to get started, and 'break out' all the other pins
you may want to connect to onto the PCB. For more details you can check
out the schematics in the Downloads page.
Power Pins
The sensor on the breakout requires 3V power. Since many customers have 5V microcontrollers like Arduino, we tossed a 3.3V regulator on the board. Its ultra-low dropout so you can power it from 3.3V-5V just fine.- Vin - this is the power pin. Since the chip uses 3 VDC, we have included a voltage regulator on board that will take 3-5VDC and safely convert it down. To power the board, give it the same power as the logic level of your microcontroller - e.g. for a 5V micro like Arduino, use 5V
-
3Vo - this is the 3.3V output from the voltage regulator, you can grab up to 100mA from this if you like
- GND - common ground for power and logic
I2C Pins
- SCL - I2C clock pin, connect to your microcontrollers I2C clock line.
- SDA - I2C data pin, connect to your microcontrollers I2C data line.
INT and ADDR Pins
- A is the I2C Address select pin. By default this is pulled up to 3.3V with a 10K resistor, for an I2C address of 0x1D. You can also connect it to the GND pin for an address of 0x1C
- I1 and I2 are the Interrupt #1 and #2 signal pins. These pins are for more advanced usage, where you want to be alerted by the chip say when data is ready to read, or if it detects a large motion. We don't have direct support in the example Arduino library for these pins, so please check the datasheet for the I2C commands
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