SPI transfer with BMA222 accelerometer

Using Arduino Networking, Protocols, and Devices
1

Hi,

I'm trying to communicate with an onboard BMA222 accelerometer. This is my first time doing SPI communication, so could anyone tell me what my code is missing? I simply get no responses.

#include "SPI.h"

void setup()
{
  pinMode(17, OUTPUT); //pin 17 is Chip select
  digitalWrite(17,HIGH);
  SPI.begin();
  SerialUSB.begin(9600);
}

void loop()
{
byte c;

digitalWrite(17, LOW);
c = SPI.transfer(0x08);  //0x08 is the temperature sensor
digitalWrite(17, HIGH);

SerialUSB.println("Temp:"+c);
}

Printing "c" results in no output. I realize I am missing SPI_MODE stuff, but I'm not sure which mode corresponds to the BMA222, and I have seen example code online that does not use it. Could that be my problem? Thanks!

2

You need to read up on how to use SPI, e.g. start here: SPI - Arduino Reference

Not sure what this is supposed to do: Does it even compile?

SerialUSB.println("Temp:"+c);
3

Interesting!

Using Arduino version 1.0.5-r2, the following program compiles, uploads and prints nothing between the ><. Anyone care to comment?

void setup(){
  byte c=48;
  Serial.begin(9600);
  Serial.print("test>");
  Serial.print("Temp"+c);
  Serial.println("<done");
}
void loop(){}
4

Thanks for the reply, That print statement is there to check what the reply from the BMA222E device is, should I be using int c instead of byte c?

I changed my main loop to:

void loop()
{
byte c;
SPI.beginTransaction(SPISettings(1000000, LSBFIRST, SPI_MODE0));
digitalWrite(17, LOW);
c = SPI.transfer(0x08);
digitalWrite(17, HIGH);
SPI.endTransaction();
SerialUSB.println("Temp:"+c);
}

But it still doesn't seem to work. Am I still missing something?

5

Yes, at the very least

Serial.print("Temp:"+c)

is not properly defined and does nothing.

Try

Serial.print("Temp: ");
Serial.println(c);
6

I still haven't managed to get this chip to work. Could there be any significance of getting a 0 as a return from SPI.transfer?