I2C addressing (7-bit and 10-bit) in Embedded C - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the difference between 7-bit and 10-bit I2C addressing?

7-bit addressing uses 7 bits to identify a device on the I2C bus, allowing up to 128 addresses. 10-bit addressing uses 10 bits, allowing more devices (up to 1024 addresses) on the bus.

beginner

How is a 7-bit I2C address transmitted on the bus?

The 7-bit address is sent in the first 7 bits of the address byte, followed by a single bit indicating read (1) or write (0).

intermediate

How does 10-bit addressing start on the I2C bus?

It starts with a special 7-bit code '11110XX' where XX are the two most significant bits of the 10-bit address, followed by a read/write bit, then the remaining 8 bits of the address.

intermediate

Why would you use 10-bit addressing instead of 7-bit?

Use 10-bit addressing when you need to connect more than 127 devices on the same I2C bus, as 7-bit addressing limits the number of unique addresses.

beginner

In embedded C, how do you typically specify a 7-bit I2C address?

You specify the 7-bit address shifted left by 1 bit, leaving the least significant bit for read/write control.

How many unique device addresses can 7-bit I2C addressing support?

A 64

B 128

C 1024

D 256

7-bit addressing supports 2^7 = 128 unique addresses.

What is the first part of the 10-bit I2C address frame?

A A special 7-bit code starting with 11110

B The full 10-bit address sent at once

C Only the lower 8 bits of the address

D A 7-bit address with read/write bit

10-bit addressing starts with a special 7-bit code '11110XX' to indicate extended addressing.

In 7-bit addressing, what does the least significant bit of the address byte represent?

A Read or write operation

B Device type

C Bus speed

D Error checking

The least significant bit indicates if the operation is a read (1) or write (0).

Why might you shift a 7-bit I2C address left by 1 in embedded C code?

A To match 10-bit addressing

B To encrypt the address

C To increase the address range

D To make room for the read/write bit

Shifting left by 1 leaves the least significant bit free for the read/write flag.

Which addressing mode allows more devices on the I2C bus?

A Both allow the same number

B 7-bit addressing

C 10-bit addressing

D Neither supports multiple devices

10-bit addressing supports up to 1024 devices, more than 7-bit's 128.

Explain how 7-bit and 10-bit I2C addressing differ in structure and usage.

Think about how many devices each can support and how the address is sent on the bus.

Describe how you would represent a 7-bit I2C address in embedded C code and why.

Remember the read/write bit is part of the address byte sent on the bus.