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Topic: I2C: Problem connecting Arduino to SDA and SCL of K24C02C (Read 731 times) previous topic - next topic

tonius

Hi!

I'm trying to connect to the K24C02C two wire serial EEPROM of a digital kitchen scale to obtain its weight measurement data.

Datasheet K24C02C: https://www.google.de/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&ved=0CDUQFjAA&url=https%3A%2F%2Fwombat-blog.googlecode.com%2Ffiles%2F20116316916429.pdf&ei=aOJFUu-HGsWrtAa63YCACw&usg=AFQjCNH28dGAAa_7RZ_y5xL5526RKhdl4Q&bvm=bv.53217764,d.Yms

I connected pin A4 to SDA and pin A5 of the Arduino to SCL of the K24C02C. See attached image for the connections on the K24C02C that I used. According to the data sheet those must be the right pins. (Interestingly, the SCL pin of the K24C02C doesn't seem to be connected to anything else on the PCB. Is that normal?)

Here's my problem: when I try to scan for I2C devices with this sketch http://playground.arduino.cc/Main/I2cScanner I only get an error: "Unknow error at address 0x1"

Sometimes it puts out multiple error messages like these with different numbers, but most of the time all I get in the console is "Unkn" and the Arduino seems to crash.

Furthermore, when I connect SDA and SCL to the Arduino, the LCD display of the scale shows messed up segments.


I'd appreciate any assistance you genius guys could give me on figuring out how to red the serial data of that thing :)

Grumpy_Mike

Quote
the SCL pin of the K24C02C doesn't seem to be connected to anything else on the PCB. Is that normal?

No it is not normal nor is it the case here.
The trace goes under the IC and emerges on the bottom side in the middle.

The IC seems to still be connected to the chip in your scales. You need to disconnect this chip (cut the traces ) before you can hope to have something else talk to it. You should also put a 4K7 pull up to 5V on both lines and remember to connect the grounds together.

tonius


Quote
the SCL pin of the K24C02C doesn't seem to be connected to anything else on the PCB. Is that normal?

No it is not normal nor is it the case here.
The trace goes under the IC and emerges on the bottom side in the middle.

The IC seems to still be connected to the chip in your scales. You need to disconnect this chip (cut the traces ) before you can hope to have something else talk to it. You should also put a 4K7 pull up to 5V on both lines and remember to connect the grounds together.


Excuse me - I'm fairly new to this. What do you mean with "The IC seems to still be connected to the chip in your scales." What chip/traces do you mean?

I want to keep the scale working and only "sniff" the live measurement data from the scale. Won't cutting traces mess that up?

Could you elaborate this a bit? Thank you!

Grumpy_Mike

The PCB traces connected to the chip go into that big black blob. There is a micro processor under that that is still connected.
However you now say you want to "snif" this chip and monster the activity on it. This means you can't scan the chip or force a responce from it. The standard I2C software is not designed for sniffing activity you will have to write your own, which I suspect you are not up to at the moment.

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