I2C Sniffer not working

July 08, 2017, 11:31:37 am

Hi there,

I am trying to get work I2C sniffer. I get an Arduino board and flash the example "Master Writer" which sends to I2C incrementing byte.

On BP I start the sniffer macro. BP with arduino are connected together (black wire - GND, yellow - SCL, orange - SDA) and I connect 2 pullup resistors 2k2 to 5V of arduino.

Arduino are sending DATA, but output of BP i just:

10-][0x10-][0x10-][0x10-][0x10-][0x10-][0x10-][0x10-][0x10-][0x10-][0x10-][0x10-][0x10-][0x10-][0x10-][0x10-][0x10-][0x10-][0x10-][0x10-][0x10-][0x10-][0x10-][0x10-][0x10-][0x10-][0x10-][0x10-][0x10-][0x10-][0x10-][0x10-][0x10-][0x10-][0x10-][0x10-][0x10-][0x10-][0x10-][0x10-][0x10-][0x10-][0x10-][0x10-][0x10-][0x10-][0x10-][0x10-][0x10-][0x10-][0x10-][0x10-][0x10-][0x10-][0x10-][

What I am doing wrong?

Re: I2C Sniffer not working

Reply #1 – July 09, 2017, 02:34:22 pm

Hi kaliginium.
You are doing nothing wrong, it is all right.
Your Bus Pirate correctly shows the hexadecimal data '0x10' followed by NACK '-' because there is not any SLAVE device.
You are using a single Arduino as MASTER while example requires a second one as SLAVE, so obviously ACK is not possible since nobody can answer there.
Please, take a look at these:

https://www.arduino.cc/en/Tutorial/MasterWriter

http://dangerousprototypes.com/docs/Bus_Pirate_I2C

As anyone can see there is a 100kHz I2C bus where Arduino send continuously the exadecimal value 0x10, nothing else.
My Bus Pirate is a revision 3 and firmware is the latest v7.1 UNSAFE_13042017 (viewtopic.php?f=28&t=8498&start=45#p66033).
In my screenshot I used the internal pull-up resistors of the Bus Pirate instead to some external ones.
This do not change nothing though.
I2C sniffer is fully functioning either SOTWARE than HARDWARE side.
In the end actually I2C sniffer is totally working exactly as supposed, nothing is wrong.

Be seeing you.

U.Sb