Single channel ADC reading in Embedded C - Mini Project: Build & Apply

Single channel ADC reading

📖 Scenario: You are working with a microcontroller that reads analog signals from a sensor. The sensor output is connected to one ADC (Analog to Digital Converter) channel. You want to read the sensor value and display it.

🎯 Goal: Build a simple embedded C program that initializes the ADC, reads a single channel value, and prints the result.

📋 What You'll Learn

Create a variable to store the ADC reading

Create a configuration variable for the ADC channel number

Write code to read the ADC value from the configured channel

Print the ADC reading value

💡 Why This Matters

🌍 Real World

Reading sensor data from analog inputs is common in embedded systems like temperature sensors, light sensors, or potentiometers.

💼 Career

Embedded developers often need to read ADC values to process sensor inputs and control hardware.

1

Create a variable to store the ADC reading

Create an integer variable called adc_value and set it to 0 to store the ADC reading.

Embedded C

int adc_value = 0;  // Your code here

Hint

Use int adc_value = 0; to create the variable.

2

Create a configuration variable for the ADC channel

Create an integer variable called adc_channel and set it to 3 to select ADC channel 3.

Embedded C

int adc_value = 0;
int adc_channel = 3;  // Your code here

Hint

Use int adc_channel = 3; to set the channel.

3

Read the ADC value from the configured channel

Write a line of code that calls the function read_adc(adc_channel) and stores the result in adc_value.

Embedded C

int adc_value = 0;
int adc_channel = 3;
adc_value = 0;  // Your code here

Hint

Use adc_value = read_adc(adc_channel); to read the ADC.

4

Print the ADC reading value

Write a line of code that prints the text "ADC Reading: " followed by the value of adc_value using printf.

Embedded C

int adc_value = 0;
int adc_channel = 3;
adc_value = read_adc(adc_channel);
// Your code here

Hint

Use printf("ADC Reading: %d\n", adc_value); to print the value.

Practice

1. What does a single channel ADC do in embedded C programming?

easy

A. It reads one analog input and converts it to a digital number.

B. It writes digital data to an analog output.

C. It reads multiple analog inputs simultaneously.

D. It converts digital signals to analog signals.

Solution

1. Step 1: Understand ADC function

   An ADC (Analog to Digital Converter) converts analog signals to digital numbers.

2. Step 2: Identify single channel meaning

   Single channel means it reads only one analog input at a time.

3. Final Answer:

   It reads one analog input and converts it to a digital number. -> Option A

4. Quick Check:

   Single channel ADC = One analog input read [OK]

Hint: Single channel ADC reads one input only [OK]

Common Mistakes:

• Confusing ADC with DAC
• Thinking ADC reads multiple inputs at once
• Mixing analog output with input reading

2. Which of the following is the correct way to start an ADC conversion in embedded C?

easy

A. ADC_Stop();

B. ADC_StartConversion();

C. ADC_Read();

D. ADC_Init();

Solution

1. Step 1: Identify function to start ADC

   Starting ADC conversion usually requires a function like ADC_StartConversion().

2. Step 2: Differentiate other functions

   ADC_Read() reads the value, ADC_Init() initializes hardware, ADC_Stop() stops ADC.

3. Final Answer:

   ADC_StartConversion(); -> Option B

4. Quick Check:

   Start ADC = ADC_StartConversion() [OK]

Hint: Start ADC with ADC_StartConversion() [OK]

Common Mistakes:

• Using ADC_Read() to start conversion
• Confusing initialization with start
• Calling ADC_Stop() instead of start

3. What will be the output of this code snippet if the ADC reads a value of 512?

int adcValue = ADC_Read();
printf("ADC Value: %d\n", adcValue);

medium

A. ADC Value: 0

B. ADC Value: 1023

C. ADC Value: 512

D. ADC Value: -512

Solution

1. Step 1: Understand ADC_Read() output

   ADC_Read() returns the current digital value from ADC, here given as 512.

2. Step 2: Print the value

   printf prints the integer value stored in adcValue, which is 512.

3. Final Answer:

   ADC Value: 512 -> Option C

4. Quick Check:

   ADC_Read() = 512 printed as is [OK]

Hint: ADC_Read() returns current ADC number [OK]

Common Mistakes:

• Assuming ADC_Read() returns max value always
• Confusing negative values in ADC reading
• Printing wrong variable or format

4. Identify the error in this ADC reading code:

ADC_Init();
int value = ADC_Read();
ADC_StartConversion();
printf("Value: %d", value);

medium

A. Variable 'value' should be float

B. ADC_Init() is missing

C. printf format specifier is wrong

D. ADC_StartConversion() should be called before ADC_Read()

Solution

1. Step 1: Check ADC function order

   ADC_StartConversion() must be called before ADC_Read() to start conversion.

2. Step 2: Analyze code sequence

   Here, ADC_Read() is called before starting conversion, so it reads old or invalid data.

3. Final Answer:

   ADC_StartConversion() should be called before ADC_Read() -> Option D

4. Quick Check:

   Start conversion before reading ADC [OK]

Hint: Start ADC conversion before reading value [OK]

Common Mistakes:

• Reading ADC before starting conversion
• Ignoring initialization step
• Wrong printf format for int

5. You want to read an analog sensor value using a single channel ADC and convert it to voltage (0-5V) with 10-bit resolution. Which code snippet correctly calculates the voltage?

int adcValue = ADC_Read();
float voltage = ?;

hard

A. voltage = (adcValue / 1023.0) * 5.0;

B. voltage = (adcValue * 5) / 1023;

C. voltage = adcValue * 5.0 / 1024.0;

D. voltage = (adcValue / 1024) * 5;

Solution

1. Step 1: Understand ADC resolution and voltage range

   10-bit ADC means values from 0 to 1023 represent 0 to 5 volts.

2. Step 2: Calculate voltage correctly

   Voltage = (adcValue / 1023.0) * 5.0; uses floating division and full scale 1023.

3. Final Answer:

   voltage = (adcValue / 1023.0) * 5.0; -> Option A

4. Quick Check:

   Voltage = ADC value / max * 5V [OK]

Hint: Divide by 1023.0 for 10-bit ADC voltage calc [OK]

Common Mistakes:

• Dividing by 1024 instead of 1023
• Using integer division instead of float
• Multiplying before dividing causing wrong result