Single channel ADC reading in Embedded C - Step-by-Step Execution

Concept Flow - Single channel ADC reading

Start ADC

↓

Wait for ADC conversion complete?

No→Wait

Yes↓

Read ADC value

↓

Use ADC value

↓

End or Repeat

This flow shows starting the ADC, waiting for conversion, reading the value, and then using it.

Execution Sample

Embedded C

ADC_Start();
while(!ADC_ConversionComplete());
int value = ADC_Read();
// Use value

This code starts ADC, waits until conversion is done, then reads the ADC value.

Execution Table

Step	Action	ADC Status	Conversion Complete?	ADC Value	Next Step
1	Call ADC_Start()	Started	No	N/A	Wait for conversion
2	Check ADC_ConversionComplete()	Started	No	N/A	Keep waiting
3	Check ADC_ConversionComplete()	Started	Yes	N/A	Read ADC value
4	Call ADC_Read()	Started	Yes	523	Use ADC value
5	Use ADC value	Started	Yes	523	End or Repeat

💡 ADC conversion complete is true, ADC value read successfully

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4	Final
ADC Status	Idle	Started	Started	Started	Started	Started
Conversion Complete	False	False	False	True	True	True
ADC Value	N/A	N/A	N/A	N/A	523	523

Key Moments - 2 Insights

Why do we need to wait for ADC_ConversionComplete() before reading the value?

Because the ADC value is only valid after conversion finishes, as shown in step 3 of the execution_table where conversion becomes true before reading.

What happens if we read ADC value before conversion is complete?

The value would be invalid or old, since conversion_complete is false in steps 1 and 2, so reading then would give wrong data.

Visual Quiz - 3 Questions

Look at the execution_table, what is the ADC value at step 4?

A 523

B N/A

C 0

D Conversion not complete

💡 Hint

Check the 'ADC Value' column at step 4 in execution_table

At which step does the ADC conversion complete become true?

A Step 1

B Step 3

C Step 2

D Step 5

💡 Hint

Look at the 'Conversion Complete?' column in execution_table

If ADC_ConversionComplete() never returns true, what happens in the execution flow?

A The program reads ADC value immediately

B The ADC value is set to zero automatically

C The program waits forever at the conversion check

D The ADC stops working

💡 Hint

Refer to the loop waiting for conversion in concept_flow and execution_table steps 1-2

Concept Snapshot

Single channel ADC reading:
1. Start ADC conversion
2. Wait until conversion complete flag is true
3. Read ADC value
4. Use the value for processing
Always wait for conversion to finish before reading.

Full Transcript

This example shows how to read a single channel ADC in embedded C. First, the ADC is started. Then the program waits in a loop checking if the conversion is complete. Once complete, the ADC value is read and can be used. The execution table traces each step, showing the ADC status, conversion flag, and value. Key points are to wait for conversion complete before reading, or else the value is invalid. The quiz questions help check understanding of when the ADC value is valid and what happens if conversion never completes.

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