Receiving a byte over UART in Embedded C - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to read a byte from UART data register.

Embedded C

uint8_t received_byte = [1];

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AUART_DR

BUART_SR

CUART_CR

DUART_BRR

Attempts:

3 left

💡 Hint

Common Mistakes

Using UART_SR (status register) instead of UART_DR.

Trying to read from UART_CR (control register).

The UART data register (UART_DR) holds the received byte. Reading from it gets the byte.

2fill in blank

medium

Complete the code to wait until a byte is received (RXNE flag set).

Embedded C

while (!([1] & (1 << RXNE_FLAG))) {}

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AUART_DR

BUART_SR

CUART_CR

DUART_BRR

Attempts:

3 left

💡 Hint

Common Mistakes

Checking RXNE flag in UART_DR instead of UART_SR.

Using UART_CR or UART_BRR which do not hold status flags.

The RXNE (Receive Not Empty) flag is in the UART status register (UART_SR). We wait until this flag is set.

3fill in blank

hard

Fix the error in the code to correctly receive a byte over UART.

Embedded C

uint8_t data;
while (!(UART_SR & (1 << [1]))) {}
data = UART_DR;

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ATXE_FLAG

BORE_FLAG

CRXNE_FLAG

DCTS_FLAG

Attempts:

3 left

💡 Hint

Common Mistakes

Using TXE_FLAG which is for transmit, not receive.

Using CTS_FLAG or ORE_FLAG which are unrelated here.

The RXNE_FLAG indicates that the receive data register is not empty and ready to be read.

4fill in blank

hard

Fill both blanks to initialize the array with the RXNE flag bit positions for each UART port and access it in the loop.

Embedded C

const int uart_rxne_flags[] = { [1] };
const char* uart_ports[] = {"UART1", "UART2", "UART3"};
for (int i = 0; i < 3; i++) {
    printf("%s RXNE flag bit: %d\n", uart_ports[i], uart_rxne_flags[[2]]);
}

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A5, 5, 5

B6, 7, 8

C5, 6, 7

Di

Attempts:

3 left

💡 Hint

Common Mistakes

Using different bit numbers for UART ports.

Not using the loop index to access the array.

The RXNE flag bit is bit 5 for all UART ports. The loop index i accesses the array.

5fill in blank

hard

Fill all three blanks to receive a byte only if RXNE flag is set, else set data to 0.

Embedded C

uint8_t data = (UART_SR & (1 << [1])) ? UART_[2] : [3];

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ARXNE_FLAG

BDR

C0

DTXE_FLAG

Attempts:

3 left

💡 Hint

Common Mistakes

Using TXE_FLAG instead of RXNE_FLAG.

Setting data to UART_DR unconditionally.

This code uses a conditional expression: if RXNE flag is set, read UART_DR, else set data to 0.