ADC conversion process (sample and hold) in Embedded C - Step-by-Step Execution

Concept Flow - ADC conversion process (sample and hold)

Start ADC Conversion

↓

Sample Input Voltage

↓

Hold Sampled Voltage

↓

Convert Analog to Digital

↓

Store Digital Value

↓

End

The ADC process starts by sampling the input voltage, holding it steady, converting it to a digital value, and then storing the result.

Execution Sample

Embedded C

void ADC_Convert() {
  float sample = SampleInput();
  HoldVoltage(sample);
  int digitalValue = ConvertToDigital(sample);
  StoreValue(digitalValue);
}

This code samples an analog input, holds it, converts it to digital, and stores the result.

Execution Table

Step	Action	Input/Variable	Result/Output
1	Start ADC Conversion	-	Begin process
2	Sample Input Voltage	Analog input voltage	sample = 2.5V
3	Hold Sampled Voltage	sample = 2.5V	Voltage held steady at 2.5V
4	Convert Analog to Digital	sample = 2.5V	digitalValue = 512 (10-bit ADC)
5	Store Digital Value	digitalValue = 512	Value stored in ADC register
6	End	-	Conversion complete

💡 Conversion ends after storing the digital value.

Variable Tracker

Variable	Start	After Step 2	After Step 3	After Step 4	Final
sample	undefined	2.5V	2.5V	2.5V	2.5V
digitalValue	undefined	undefined	undefined	512	512

Key Moments - 2 Insights

Why do we need to hold the voltage after sampling?

Holding the voltage keeps the sampled value steady during conversion, as shown in step 3 of the execution table.

What does the digitalValue represent after conversion?

digitalValue is the number representing the analog voltage in digital form, as seen in step 4 and 5.

Visual Quiz - 3 Questions

Look at the execution table, what is the value of 'sample' after step 2?

A undefined

B 512

C 2.5V

D 0V

💡 Hint

Check the 'sample' variable in the variable_tracker after step 2.

At which step is the analog voltage converted to a digital value?

A Step 4

B Step 3

C Step 2

D Step 5

💡 Hint

Look at the 'Action' column in the execution_table for conversion.

If the input voltage changes during holding, what would happen to the digitalValue?

A digitalValue would be accurate regardless

B digitalValue would be incorrect because voltage is not steady

C digitalValue would be zero

D Conversion would stop immediately

💡 Hint

Refer to the importance of holding voltage steady in step 3.

Concept Snapshot

ADC Conversion Process (Sample and Hold):
1. Start conversion
2. Sample input voltage
3. Hold voltage steady
4. Convert analog to digital
5. Store digital value
Holding ensures stable conversion.

Full Transcript

The ADC conversion process begins by starting the conversion. The system samples the analog input voltage, for example 2.5 volts. Then it holds this sampled voltage steady to prevent changes during conversion. Next, the analog voltage is converted into a digital number, such as 512 for a 10-bit ADC. Finally, the digital value is stored in a register, completing the conversion process. Holding the voltage is important to get an accurate digital value. If the voltage changes during holding, the digital result would be incorrect.