Communicating with Arduino over UART in Raspberry Pi - Step-by-Step Execution

Concept Flow - Communicating with Arduino over UART

Start Raspberry Pi UART Setup

↓

Open UART Port

↓

Send Data to Arduino

↓

Arduino Receives Data

↓

Arduino Sends Response

↓

Raspberry Pi Reads Response

↓

Close UART Port

↓

End

This flow shows how Raspberry Pi opens a UART port, sends data to Arduino, waits for a response, reads it, and then closes the port.

Execution Sample

Raspberry Pi

import serial

ser = serial.Serial('/dev/serial0', 9600)
ser.write(b'Hello Arduino')
response = ser.readline()
print(response.decode())
ser.close()

This code opens UART, sends 'Hello Arduino', reads a line from Arduino, prints it, then closes UART.

Execution Table

Step	Action	UART Port State	Data Sent	Data Received	Output
1	Open UART port '/dev/serial0' at 9600 baud	Open
2	Send bytes b'Hello Arduino'	Open	b'Hello Arduino'
3	Wait and read a line from Arduino	Open	b'Hello Arduino'	b'Hi Pi\n'
4	Decode received bytes to string	Open	b'Hello Arduino'	b'Hi Pi\n'	Hi Pi
5	Print decoded response	Open	b'Hello Arduino'	b'Hi Pi\n'	Hi Pi
6	Close UART port	Closed	b'Hello Arduino'	b'Hi Pi\n'	Hi Pi

💡 UART port closed after communication completes

Variable Tracker

Variable	Start	After Step 2	After Step 3	After Step 4	Final
ser	None	Serial('/dev/serial0', 9600)	Serial('/dev/serial0', 9600)	Serial('/dev/serial0', 9600)	Closed
Data Sent		b'Hello Arduino'	b'Hello Arduino'	b'Hello Arduino'	b'Hello Arduino'
Data Received			b'Hi Pi\n'	b'Hi Pi\n'	b'Hi Pi\n'
response			b'Hi Pi\n'	Hi Pi\n	Hi Pi\n

Key Moments - 3 Insights

Why do we use b'Hello Arduino' instead of 'Hello Arduino' when sending data?

UART communication sends bytes, not strings. Using b'' converts the string to bytes, which matches the UART data format, as shown in step 2 of the execution_table.

Why do we decode the received data before printing?

The data received from UART is in bytes (step 3). Decoding converts bytes to a readable string (step 4), so print shows human-readable text.

What happens if we forget to close the UART port?

The port remains open, which can block other programs from using it. Step 6 shows closing the port to free it for future use.

Visual Quiz - 3 Questions

Look at the execution_table at step 3. What data does Raspberry Pi receive from Arduino?

A b'Hi Pi\n'

B b'Hello Arduino'

C b'' (empty)

D b'Error'

💡 Hint

Check the 'Data Received' column at step 3 in the execution_table.

At which step is the UART port closed?

A Step 4

B Step 6

C Step 2

D Step 5

💡 Hint

Look at the 'UART Port State' column to find when it changes to 'Closed'.

If we send 'Hello Arduino' without b'' (bytes), what will happen?

A Data sends correctly

B Data is sent as string automatically

C Program raises an error

D UART port closes immediately

💡 Hint

Refer to key_moments about why bytes are needed for UART sending.

Concept Snapshot

Communicating with Arduino over UART on Raspberry Pi:
- Open UART port with serial.Serial('/dev/serial0', baudrate)
- Send bytes using ser.write(b'data')
- Read response with ser.readline()
- Decode bytes to string before printing
- Close port with ser.close() to free resource

Full Transcript

This visual execution shows how Raspberry Pi communicates with Arduino using UART. First, the UART port '/dev/serial0' is opened at 9600 baud. Then, Raspberry Pi sends the byte string b'Hello Arduino' to Arduino. Arduino responds with b'Hi Pi\n', which Raspberry Pi reads using readline(). The received bytes are decoded to a string 'Hi Pi\n' for printing. Finally, the UART port is closed to finish communication. Key points include sending bytes, decoding received bytes, and closing the port to avoid resource conflicts.