I2c accelerometer voltage

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1

Hello,
I’ve recently purchased an i2c compatible accelerometer and am wondering what values SDA, SCL and any other pin on the Arduino/sensor should be outputting as I’d like to test it with a multimeter. I’m just using a standard i2c scanner code:

`
#include <Wire.h>

// Set I2C bus to use: Wire, Wire1, etc.
#define WIRE Wire

void setup() {
WIRE.begin();

Serial.begin(9600);
while (!Serial)
delay(10);
Serial.println(“\nI2C Scanner”);
}

void loop() {
byte error, address;
int nDevices;

Serial.println(“Scanning…”);

nDevices = 0;
for(address = 1; address < 127; address++ )
{
WIRE.beginTransmission(address);
error = WIRE.endTransmission();

if (error == 0)
{
  Serial.print("I2C device found at address 0x");
  if (address<16)
    Serial.print("0");
  Serial.print(address,HEX);
  Serial.println("  !");

  nDevices++;
}
else if (error==4)
{
  Serial.print("Unknown error at address 0x");
  if (address<16)
    Serial.print("0");
  Serial.println(address,HEX);
}

}
if (nDevices == 0)
Serial.println(“No I2C devices found\n”);
else
Serial.println(“done\n”);

delay(5000); // wait 5 seconds for next scan
}

`

Here is the link to the accelerometer: PiicoDev 3-Axis Accelerometer LIS3DH | Core Electronics Australia

I’m also using an uno r3 as my master device.

2

Hi Matthew
This seems to be a 3.3V device ie; there does not seem to be an on board regulator. The description does not explicitly say so or say exactly what the operating voltage range is. But the screen print says “3.3V” so that must be it.

Provided the pull up resistors are connected (I think they are by default and you cut a track to disconnect) you should measure whatever is applied to the 3.3V point.

A multimeter will be too slow to measure any logic traffic in SDA or SCL. I think “INT” pins are interrupts and I have no idea what you would measure here. I would think they might be active LOW using external pull ups.
Cheers Bob

3

Hello bob! Would there be any other way of testing that the SDA and SCL pins are outputting the right values?

4

Hi Matthew
Oscilloscope will show traffic and voltage levels but not what that traffic actually is.
A Logic analyser I think will decode the traffic.
A Logic probe will give a LED indication of traffic presence (blinks) but not actual voltage levels or decoding.

Google “logic probe” and you could probably make one, They are really not that complicated. I don’t think very expensive to purchase either.
Cheers Bob

1 Like
5

Thanks!

1 Like