i2cdetect for device scanning in Raspberry Pi - Step-by-Step Execution

Concept Flow - i2cdetect for device scanning

Start i2cdetect command

↓

Scan I2C bus addresses 0x03 to 0x77

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Send probe to each address

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Check for device response

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Mark address

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Display full address map

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End

The i2cdetect command scans all possible I2C addresses on the bus, probing each one to see if a device responds, then shows a map of detected devices.

Execution Sample

Raspberry Pi

sudo i2cdetect -y 1

This command scans the I2C bus number 1 and shows which addresses have devices connected.

Execution Table

Step	Address Probed	Device Response	Mark on Map
1	0x03	No	--
2	0x04	No	--
3	0x05	No	--
4	0x20	Yes	20
5	0x21	No	--
6	0x3C	Yes	3c
7	0x40	No	--
8	0x77	No	--
9	All addresses scanned	Scan complete	Map displayed

💡 All addresses from 0x03 to 0x77 scanned; devices found at 0x20 and 0x3C; scan ends.

Variable Tracker

Variable	Start	After Step 4	After Step 6	Final
Detected Devices	[]	[0x20]	[0x20, 0x3C]	[0x20, 0x3C]

Key Moments - 3 Insights

Why do some addresses show '--' instead of a number?

Addresses marked '--' mean no device responded at that address during the scan, as shown in execution_table rows 1-3 and 5,7,8.

Why does the scan start at address 0x03 and not 0x00?

Addresses below 0x03 are reserved or not valid for devices, so i2cdetect skips them, as seen in the concept_flow scanning range.

What does the 'Yes' response mean during probing?

'Yes' means a device acknowledged the probe at that address, so it is marked on the map, like at 0x20 and 0x3C in execution_table steps 4 and 6.

Visual Quiz - 3 Questions

Look at the execution_table, what is the device response at address 0x21?

A Yes

B Error

C No

D Not scanned

💡 Hint

Check execution_table row 5 for address 0x21 response.

At which step does the first device get detected?

A Step 2

B Step 4

C Step 6

D Step 8

💡 Hint

Look at execution_table rows 1-6 and find the first 'Yes' response.

If a device was connected at address 0x40, how would the map mark it?

A It would show '40'

B It would show '--'

C It would show 'xx'

D It would be skipped

💡 Hint

Devices that respond are marked by their hex address, as in execution_table step 4 and 6.

Concept Snapshot

i2cdetect scans I2C bus addresses from 0x03 to 0x77.
It sends a probe to each address.
If a device responds, the address is shown.
Addresses with no response show '--'.
Use 'sudo i2cdetect -y <bus>' to scan.
Detected devices help confirm hardware connections.

Full Transcript

The i2cdetect command is used on Raspberry Pi to scan the I2C bus for connected devices. It checks addresses from 0x03 to 0x77 by sending a probe to each. If a device responds, its address is shown in the output map; otherwise, '--' is shown. This helps users find which devices are connected and at what addresses. The scan ends after all addresses are checked. For example, running 'sudo i2cdetect -y 1' scans bus 1 and lists detected devices. Addresses below 0x03 are skipped because they are reserved. The output map is a grid showing addresses with devices or empty spots. This tool is essential for troubleshooting I2C connections on Raspberry Pi.