Clock polarity and phase (CPOL, CPHA) in Embedded C - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to set the clock polarity (CPOL) bit to 1.

Embedded C

SPI->CR1 |= (1 << [1]);

Drag options to blanks, or click blank then click option'

A2

B1

C0

D3

Attempts:

3 left

💡 Hint

Common Mistakes

Using bit 0 instead of bit 1 for CPOL.

Confusing CPOL with CPHA bit positions.

The CPOL bit is usually bit 1 in the SPI control register CR1. Setting it to 1 configures the clock polarity.

2fill in blank

medium

Complete the code to clear the clock phase (CPHA) bit.

Embedded C

SPI->CR1 &= ~(1 << [1]);

Drag options to blanks, or click blank then click option'

A3

B1

C2

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Clearing the wrong bit position.

Using |= instead of &=~ to clear the bit.

The CPHA bit is usually bit 0 in the SPI control register CR1. Clearing it sets the clock phase to 0.

3fill in blank

hard

Fix the error in the code to set CPOL and CPHA correctly.

Embedded C

SPI->CR1 = (1 << [1]) | (1 << [2]);

Drag options to blanks, or click blank then click option'

A0

B1

C2

D3

Attempts:

3 left

💡 Hint

Common Mistakes

Setting wrong bit positions for CPOL or CPHA.

Using assignment instead of bitwise OR.

CPOL is bit 1 and CPHA is bit 0. The code should set both bits 1 and 0.

4fill in blank

hard

Fill both blanks to configure SPI with CPOL=1 and CPHA=0 using bitwise operations.

Embedded C

SPI->CR1 = (1 << [1]) & ~(1 << [2]);

Drag options to blanks, or click blank then click option'

A1

B0

C2

D3

Attempts:

3 left

💡 Hint

Common Mistakes

Using OR instead of AND to clear a bit.

Mixing up CPOL and CPHA bit positions.

Set CPOL (bit 1) by shifting 1 left by 1, and clear CPHA (bit 0) by clearing bit 0.

5fill in blank

hard

Fill all three blanks to create a mask that sets CPOL and CPHA bits and clears bit 2.

Embedded C

SPI->CR1 = ((1 << [1]) | (1 << [2])) & ~(1 << [3]);

Drag options to blanks, or click blank then click option'

A1

B0

C2

D3

Attempts:

3 left

💡 Hint

Common Mistakes

Not using parentheses causing wrong bitwise precedence.

Setting bit 2 instead of clearing it.

Set CPOL (bit 1) and CPHA (bit 0), and clear bit 2 to disable unwanted features.