# I2C Protocol

## Introduction

* Multi master multi slave communication , 128 devices maximum because of the data frame having a fixed bits for addresses
* Maximum of 3mbps , synchronous data transfer protocol
* has start and stop conditions , and a data frame format 

## configuration / connection

* Multi master multi slave

<figure><img src="/files/MMy14Je7XxhriLmUo29w" alt=""><figcaption><p>I2C connection</p></figcaption></figure>

* SDA - Data line  , SCL - Serial clock
* Open drain / open collector configuration / pull up pull down is required
* In open drain (above image) a pull up resistor is used for idle state and pulled low when required
* uses 4.7kohm resisitor typically

## Details

#### Communication:

* start condition : SDA is pulled low keeping scl (clk) high (idle)&#x20;
* Master sends 7 bit (0-127) slave address first with read/write and waits for ACK/NACK from slave
* slave pulls sda low to indicate ACK&#x20;
* Master sends or recieves  a data frame 8 bit  waits for ack or nack
* slave ACK once recieved&#x20;
* Master stop condition is issued: SDA is high before SCL

<figure><img src="/files/5uFVJAgs7lgZdhN3Z1s7" alt=""><figcaption></figcaption></figure>

### Arbitration / handling multiple slaves from collision

* In Multi master configuration SDA is monitored and if its low then devices wont send data

## Usage and limitations

* As the name suggests its a very low speed communication meant for chip to chip in a pcb
* used in sensors , eeprom etc
* 400kbps in the fast mode&#x20;

## References:

{% embed url="<https://www.ti.com/lit/an/slva704/slva704.pdf?ref_url=https%3A%2F%2Fwww.google.com%2F&ts=1675301205556>" %}
TI i2c explanation
{% endembed %}

{% embed url="<https://www.analog.com/en/technical-articles/i2c-primer-what-is-i2c-part-1.html>" %}

{% embed url="<https://www.circuitbasics.com/basics-of-the-i2c-communication-protocol/>" %}

{% embed url="<https://articles.saleae.com/logic-analyzers/spi-vs-i2c-protocol-differences-and-things-to-consider#i2c>" %}

{% embed url="<https://www.youtube.com/watch?ab_channel=FoolishEngineer&v=UP0aeeuz65U>" %}


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