MMA7455L accelerometer breakout board

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Project Summary
Name: MMA7455L accelerometer breakout board
Buy it: Get one for $15 at Seeed Studio
Price: $15
Status: Test production
Manufacturing: Shipping
Forum: MMA7455L accelerometer breakout board Forum
Mma7455l-breakout.jpg

Get the MMA7455L breakout board for $15.

The MMA7455L is an inexpensive 3-axis accelerometer ($2 in 1s), with adjustable measurement range of 2/4/8g.

We used this chip in the USB POV Toy to sync the POV display to the speed of the user's hand motions. It only comes in a leadless LGA-14 package. It's a challenging chip to solder, so we thought a inexpensive breakout board might be useful.

  • 2/4/8g selectable
  • 10bit or 8bit output
  • force and pulse detection with interrupt
  • I2C and SPI interface
  • 3.3volts
  • Arduino example

Get the MMA7455L breakout board for $15.

Read about the design below.

Contents

Hardware

Mma7455-bo-v1a-cct-cropped.png

Click for a full size schematic image. Schematic and PCB were designed with the freeware version of Cadsoft Eagle.

MMA7455L

MMA7455L is an inexpensive but feature packed digital output accelerometer with adjustable measurement range of 2/4/8g. It can communicate with microcontrollers using the SPI or I2C interface.

Decoupling capacitors (C1,C2,C3,C4) were used for each supply pin (AVdd and DVdd_IO) of MMA7455L. A pair of 10uF and 0.1uF capacitors is recommended for each supply pin to decouple the power source.

Pin 4 (IADDR0) of MMA7455L is an optional I2C Address Bit 0 pin. However, this pin is not enabled at the default state. Some factory programming (by Freescale) is required to be able to use this pin to set the I2C Address Bit 0. Since enabling this pin will take another production step, we decided to just tie it to VDD.

SPI INTERFACE

The following pins are required to use the SPI interface

SPI MMA7455L Description
MOSI SDA/SDI/SDO Master Out, Slave In
MISO SDO Master In, Slave Out
CLK SCL/SPC Clock signal
CS CS Chip Select

I2C INTERFACE

The following pins are required to use the I2C interface

I2C MMA7455L Description
SDA SDA/SDI/SDO Serial Data
SCL SCL/SPC Clock signal

It is recommended to use external pullup resistors for both the SDA and SCL pins if I2C interface is used.

Recommended value for the pullup resistors is 4.7 kohms.

PCB

Mma7455-bo-v1a-brd.png

Click the picture for a full size placement image.

Usb-accel.jpg

The design is simple enough, but the LGA-14 chip is a challenge to solder. We successfully soldered several of these using this technique:

  1. Flux the pads then add a little solder to the PCB, maybe mop it up if it's more than a thin layer
  2. Flux the chip and put a bit of solder on the pads. Mop up all of it with copper wick, you just want the pads tinned or the whole thing will float on solder bubbles
  3. Flux the chip and the board
  4. Heat up the board and the chip with a hot air rework tool. The solder should turn liquid
  5. Now quickly pace the chip on the PCB, don't worry about alignment yet
  6. Heat it with hot air, keep it moving so you don't scorch the PCB. Tap the chip for alignment. We've heard you can tap the board and stuff snaps into place, but it doesn't work for us
  7. When it looks perfect, wait. If you move the board too soon it will misalign. This happened twice the first time

Partlist

PartQuantityValuePackage
C1, C3210uF/6v tantalumSMC_A
C2, C420.1uFC805
U11MMA7455LLGA-14

The latest sources and distributors are in the master partlist. See something missing? Please let us know.

Demos

Get one!

Mma7455l-breakout.jpg

Get this breakout board for $15. Your purchases at Seeed Studio keep the open source project coming, we sincerely appreciate your support!

Resources

License

  • CC-0, reference boards shouldn't be copyrighted!