Memory-mapped I/O concept in Embedded C - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a pointer to a memory-mapped I/O register at address 0x40021000.

Embedded C

volatile unsigned int *reg = (volatile unsigned int *)[1];

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A0x20000000

B0x40021000

C0x60000000

D0x10000000

Attempts:

3 left

💡 Hint

Common Mistakes

Using an incorrect address that does not map to the desired peripheral.

The address 0x40021000 is the correct base address for the memory-mapped I/O register in this example.

2fill in blank

medium

Complete the code to write the value 0x01 to the memory-mapped register pointed by reg.

Embedded C

*reg = [1];

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A0x10

B0xFF

C0x01

D0x00

Attempts:

3 left

💡 Hint

Common Mistakes

Writing 0x10 or 0xFF which sets other bits unintentionally.

Writing 0x01 sets the first bit of the register, often used to enable a feature.

3fill in blank

hard

Fix the error in the code to correctly read the value from the memory-mapped register.

Embedded C

unsigned int value = [1]reg;

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A*

B&

C->

D.

Attempts:

3 left

💡 Hint

Common Mistakes

Using ® which gives the address of the pointer variable, not the register.

The dereference operator * is used to read the value pointed to by reg.

4fill in blank

hard

Fill both blanks to define a pointer to a volatile 8-bit register at address 0x50000010 and write 0xFF to it.

Embedded C

volatile [1] *reg8 = (volatile [2] *)0x50000010;
*reg8 = 0xFF;

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Aunsigned char

Bunsigned int

Cchar

Dint

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'unsigned int' which is typically 32-bit and incorrect for 8-bit registers.

Using 'unsigned char' defines an 8-bit volatile pointer suitable for 8-bit registers.

5fill in blank

hard

Fill all three blanks to create a macro that reads a 16-bit memory-mapped register at a given address.

Embedded C

#define READ_REG16(addr) (*(volatile [1] *)[2])

unsigned short val = READ_REG16([3]);

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Aunsigned short

B(addr)

C0x40002000

Dunsigned int

Attempts:

3 left

💡 Hint

Common Mistakes

Using unsigned int which is 32-bit, or wrong addresses.

The macro casts the address to a volatile unsigned short pointer and dereferences it. The address passed to the macro is 0x40002000.