Connecting BMA180 accelerometer to Arduino Mega

Other Hardware Sensors
1

Hi,

I would like to confirm or correct my connections from a BMA180 to an Arduino Mega. I am using an I2C sample sketch, however the output x, y and z values are all zero so I think my connections are wrong.

My connections are:-

BMA180 Arduino Mega

VDD to 3.3V
GND to GND
INT not connected
CS to 3.3V
SCK to Analog 5 pin
SDO to GND
SDI to Analog 4 pin
VIO to 3.3V

Thanks in advance.

Steve

2

Don't forget that I2C needs pull-up resistors on the bus. About 4.7k on each wire is a good starting point with 1.8k to 10k being a good range. Only one pull-up per wire.

3

Thanks John.

I got it working :slight_smile:

I discovered that the Mega uses pins 20 and 21 for I2C interface and not pins 4 and 5. So I just swaped the SDI and SCK to pins 20 and 21 and it worked. Should I still add the pull up resistors or are there pull up resistors already built into the Arduino I2C pins?

Once again, thankyou for your time.

4

The ATmega processor does have built-in pull-up resistors that can be enabled but when I looked at the Arduino 1.0 Wire library I didn't see any place where they were enabled. Perhaps your accelerometer module has pull-ups. You'd have to look at the schematic to find out.

5

Thanks John,

The schematic of my BMA 180 accelerometer board does not show any pull up so I will add them. The x, y and z values don't seem to mean anything, apart from changing when I move the accelerometer. However the temperature reading seems accurate.

Thankyou for your time.