Why serial communication is needed in Embedded C - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to send a byte over serial communication.

Embedded C

void sendByte(unsigned char data) {
    while(![1]); // Wait until transmit buffer is empty
    TXREG = data;
}

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

ARXIF

BRCIF

CTXIE

DTXIF

Attempts:

3 left

💡 Hint

Common Mistakes

Using RXIF which is for receive buffer, not transmit.

The TXIF flag indicates the transmit buffer is empty and ready to send data.

2fill in blank

medium

Complete the code to initialize serial communication at 9600 baud rate.

Embedded C

void initSerial() {
    SPBRG = [1]; // Set baud rate generator
    TXSTA = 0x24; // Enable transmitter, BRGH=1
    RCSTA = 0x90; // Enable serial port and continuous receive
}

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

A25

B12

C51

D34

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong SPBRG value causing incorrect baud rate.

For 9600 baud with 4MHz clock and BRGH=1, SPBRG is set to 25.

3fill in blank

hard

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

Embedded C

unsigned char receiveByte() {
    while(![1]); // Wait until data is received
    return RCREG;
}

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ATXIF

BTXIE

CRCIF

DRCIE

Attempts:

3 left

💡 Hint

Common Mistakes

Using TXIF which is for transmit, not receive.

RCIF flag indicates that a byte has been received and is ready to read.

4fill in blank

hard

Complete the code to handle overrun error when receiving a byte over serial communication.

Embedded C

unsigned char safeReceive() {
    if([1]) {
        [2] = 0;
        [2] = 1;
    }
    while(!RCIF);
    return RCREG;
}

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AOERR

BCREN

CFERR

DTXEN

Attempts:

3 left

💡 Hint

Common Mistakes

Using FERR, which is cleared by reading RCREG, not by toggling CREN.

Not handling OERR properly.

The OERR (overrun error) flag must be cleared by momentarily disabling continuous receive enable (CREN).

5fill in blank

hard

Complete the code to enable transmit interrupt for serial communication.

Embedded C

void enableTXInt() {
    INTCONbits.[1] = 1;
    INTCONbits.[2] = 1;
    PIE1bits.[3] = 1;
}

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

AGIE

BPEIE

CTXIE

DRCIE

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting GIE or PEIE, required for any interrupts.

INTCONbits.GIE (global), INTCONbits.PEIE (peripheral), and PIE1bits.TXIE (TX specific) must all be set.

Practice

1. Why is serial communication commonly used in embedded systems?

easy

A. Because it only works with wireless devices

B. Because it sends data all at once using many wires

C. Because it requires no physical connection between devices

D. Because it uses fewer wires to send data bit by bit

Solution

1. Step 1: Understand serial communication basics

   Serial communication sends data one bit at a time, which means it uses fewer wires compared to parallel communication.

2. Step 2: Relate to embedded systems needs

   Embedded systems often have limited pins and need simple wiring, so sending data bit by bit with fewer wires is ideal.

3. Final Answer:

   Because it uses fewer wires to send data bit by bit -> Option D

4. Quick Check:

   Serial communication = fewer wires [OK]

Hint: Serial means one bit at a time, so fewer wires needed [OK]

Common Mistakes:

• Thinking serial sends all data at once
• Confusing serial with wireless communication
• Assuming no wires are needed

2. Which of the following is the correct way to initialize UART serial communication in embedded C?

easy

A. uart_start(9600);

B. Serial.begin(9600);

C. UART_Init(9600);

D. init_uart(9600);

Solution

1. Step 1: Identify standard UART initialization function

   In embedded C, UART is commonly initialized with a function like UART_Init that takes baud rate as argument.

2. Step 2: Check syntax correctness

   UART_Init(9600); is a typical correct syntax, while others are either Arduino style or made-up functions.

3. Final Answer:

   UART_Init(9600); -> Option C

4. Quick Check:

   UART_Init is standard init function [OK]

Hint: Look for standard C style function names for UART [OK]

Common Mistakes:

• Using Arduino style Serial.begin in embedded C
• Using undefined function names
• Missing baud rate parameter

3. What will be the output of this embedded C code snippet if serial communication sends the character 'A'?

char received = UART_Read();
printf("Received: %c", received);

medium

A. Received: A

B. Received: 65

C. Received: \0

D. Compilation error

Solution

1. Step 1: Understand UART_Read() behavior

   UART_Read() reads one byte from serial and returns it as a char, so if 'A' is sent, it returns 'A'.

2. Step 2: Analyze printf output

   Using %c in printf prints the character itself, so it will print 'Received: A'.

3. Final Answer:

   Received: A -> Option A

4. Quick Check:

   UART_Read returns char, %c prints char [OK]

Hint: %c prints char, UART_Read returns char [OK]

Common Mistakes:

• Confusing %c with %d in printf
• Expecting numeric ASCII code output
• Assuming UART_Read returns integer

4. Identify the error in this code snippet for serial communication setup:

void setup() {
  UART_Init();
  UART_SetBaudRate(9600);
}

medium

A. UART_Init() needs baud rate parameter

B. UART_SetBaudRate() should be called before UART_Init()

C. UART_Init() and UART_SetBaudRate() cannot be used together

D. No error, code is correct

Solution

1. Step 1: Check UART_Init() function usage

   Typically, UART_Init() requires the baud rate as a parameter to configure communication speed.

2. Step 2: Analyze function calls order and necessity

   Calling UART_SetBaudRate() separately is redundant if UART_Init() already sets baud rate; missing parameter causes error.

3. Final Answer:

   UART_Init() needs baud rate parameter -> Option A

4. Quick Check:

   UART_Init(baud) required [OK]

Hint: UART_Init usually needs baud rate parameter [OK]

Common Mistakes:

• Calling UART_Init without parameters
• Assuming baud rate can be set after init
• Thinking both functions are always needed

5. You want to connect a sensor with only 3 pins to a microcontroller over a long distance. Why is serial communication preferred over parallel communication in this case?

hard

A. Because parallel communication is faster and better for long distances

B. Because serial communication uses fewer wires, reducing complexity and noise over long cables

C. Because serial communication requires more wires, which improves reliability

D. Because parallel communication can only send data bit by bit

Solution

1. Step 1: Consider wiring complexity for long distance

   Long cables are prone to noise; fewer wires mean less interference and simpler connections.

2. Step 2: Compare serial and parallel communication

   Serial sends data bit by bit using fewer wires, making it better for long distances and limited pins.

3. Step 3: Eliminate incorrect options

   Parallel communication uses many wires and is not ideal for long distances; serial communication does not require more wires.

4. Final Answer:

   Because serial communication uses fewer wires, reducing complexity and noise over long cables -> Option B

5. Quick Check:

   Fewer wires = better for long distance [OK]

Hint: Fewer wires means less noise and simpler long-distance wiring [OK]

Common Mistakes:

• Thinking parallel is better for long distances
• Assuming serial needs more wires
• Confusing bit by bit sending with parallel