How to work with I2C 'Two Wire Interface' Devices!

Code shown in the video:

Compass: HMC6352
EEPROM: 24LC256
RTC: DS1307


Thanks to all the Patrons for dropping a few bucks in the tip jar to help make these videos happen!

For inquiries or design services:

[smaniac]

"...bought a component claiming to be a simple 2-wire interface..." => Bullseye.
"Don't want to know how to build I2C, just communicate..." => Bullseye.
Awesome tutorial => Bullseye.

Can't wait to get my astonishingly cheap/powerful IMU working! Gyro + 3axis acc + mag + barometer = programming challenge foolhardily accepted.

Thanks man! Couldn't do it without Y-tuters like yourself.

[Kevindarrah]

@MazlumOguz yea, I agree, but I don't have any SPI devices, when I get something, a video will be made

[Kevindarrah]

@WakeUpWolfgang yea, it took a while to make, hopefully it helps!

[Kevindarrah]

got it from futurlec, thanks! glad it helped!!

[Kevindarrah]

that would be cool, to actually bit bang your way through the I2C communication. Not sure if I'll ever have the time to do something like that.. we'll see

[Kevindarrah]

@TheSchetsofiel69 absolutely! I should've showed that! You can setup another mcu as a slave device. See the arduino reference help

[Kevindarrah]

yea, it just gets a little confusing, especially when you're looking at timing diagrams using bits

[Kevindarrah]

@friendsonearth I'm not sure... I've never seen that happen.

[AlanClegg]

In addition to the MSB, LSB version, you can also do something like:

data = low | high << 8;

This shifts the high bits up 8 bits and ORs ( | ) the low bits in, giving you the result you want.

Simple, easy to read and understandable. :)

[michaelhawthorne]

Nice explanation, thank you.
I really need to get my head around this I2C stuff, that cleared away a lot of the mud.

[AlanClegg]

Another note... the way that the RTC uses the 4 bits for "10 seconds" and 4 bits for "1 seconds" sets you up perfectly if you are using hex. ;-)

since 55 seconds would be 0x55 .. and 18 seconds would be 0x18 (note that 4 bits (a nibble) is one hex character.

For the other items (AM, PM, etc) you would probably want to use a struct{} to build and set it up easily.

[TranscendentBen]

I've been listening and not paying much attention (the Adafruit librariies for Arduino make I2C so easy, see my video from February), then I heard "I didn't have to do this for loop" at 19:30 and started to look at your code ... Oh, man, you make the original K&R ("The C Programming Language") formatting look like The Ultimate In Structured Programming!

Please, people,
Indent your loop contents,
Just a little, please!

[Kevindarrah]

@friendsonearth don't know what you mean, the delay() is arduino, the real time clock is the device ds1307, and there is also a clock signal line for the devices, so...?

[Elixz]

You just have to know that for the 4 lower bits the values 1, 2, 4, 8 are and the upper bits are 10, 20, 40, 80. So you can roughly see what the value is in an instant

[Kevindarrah]

cool, make sure you let me if it works out

[NA]

Thanks for the video! My Icom 706 uses I2C, and I would like to be able to build devices to communicate to it. This gave me some good insight.

[Kevindarrah]

@JurriaanPetersen haha, I knew somebody was gonna be mad about all my smack talk...

[SirArghPirate]

I guess it would be rude to ask about a demonstration on this "bit banging", but do you know any videos that explain this to great detail? The problem I was having was identifying the device, and I finally found a sketch for arduino to do it, but I didn't understand how it worked. For my part this kind of insight is very helpful. Great videos btw, just subscribed! :)

[timjackson]

Thanks Kevin very clear on what could be an intimidating topic for us newbies. I found it very helpfull - muchos gracias

[rmknh]

Hi this is very helpful video.
I had trying to get a simple communication between Arduino Diecimila and PIC24 through I2C. Its almost 3 months completed in search of communicating these devises.
I am in a serious need of help I need a simple communication between pic24fj256ga110 a 100 pin device with Arduino, both of these devise are individual powered supplied and for pic I am using MPLAB IDE.