UART interrupt-driven communication in Embedded C - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to enable UART receive interrupt.

Embedded C

UART->CR1 |= [1];

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AUART_CR1_TXEIE

BUART_CR1_RXNEIE

CUART_CR1_TE

DUART_CR1_RE

Attempts:

3 left

💡 Hint

Common Mistakes

Using UART_CR1_TXEIE which enables transmit interrupt instead of receive.

Using UART_CR1_TE or UART_CR1_RE which enable transmitter or receiver but not interrupts.

UART_CR1_RXNEIE enables the receive data register not empty interrupt.

2fill in blank

medium

Complete the code to clear the UART receive interrupt flag inside the ISR.

Embedded C

if (UART->ISR & UART_ISR_RXNE) {
    uint8_t data = UART->RDR;
    UART->ICR = [1];
}

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AUART_ICR_IDLECF

BUART_ICR_RXNECF

CUART_ICR_ORECF

DUART_ICR_TCCF

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to clear RXNE flag manually which is cleared by reading RDR.

Clearing unrelated flags like IDLE or transmission complete.

Reading RDR clears RXNE flag automatically, but overrun error flag (ORE) must be cleared manually using UART_ICR_ORECF.

3fill in blank

hard

Fix the error in the UART interrupt handler to correctly read received data.

Embedded C

void USART1_IRQHandler(void) {
    if (UART->ISR & [1]) {
        uint8_t received = UART->RDR;
        process(received);
    }
}

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AUART_ISR_TXE

BUART_ISR_PE

CUART_ISR_TC

DUART_ISR_RXNE

Attempts:

3 left

💡 Hint

Common Mistakes

Using TXE which is transmit data register empty flag.

Using TC which is transmission complete flag.

UART_ISR_RXNE indicates that data is ready to be read from the receive data register.

4fill in blank

hard

Fill both blanks to create a dictionary comprehension that maps received bytes to their ASCII codes only if the byte is a letter.

Embedded C

received_map = {byte: ord(byte) for byte in buffer if byte [1] [2]

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A>=

B'a'

C'A'

D<=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<=' instead of '>=' causing wrong filtering.

Using 'a' which is lowercase and misses uppercase letters.

The comprehension filters bytes greater or equal to 'A' to include letters.

5fill in blank

hard

Fill all three blanks to build a dictionary comprehension that maps uppercase letters to their ASCII codes only if the code is less than 91.

Embedded C

uppercase_map = { [1] : [2] for [3] in buffer if ord([3]) < 91 }

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Achar

Bord(char)

Dbyte

Attempts:

3 left

💡 Hint

Common Mistakes

Using different variable names inconsistently.

Not using ord() for the value.

The comprehension uses 'char' as key and ord(char) as value for letters with ASCII less than 91 (uppercase letters).