Signals and ADC

Analog vs Digital

Property	Analog	Digital
Values	Continuous (infinite range)	Discrete (finite steps)
Examples	Temperature, sound, light intensity	Binary data, GPIO logic levels
Noise sensitivity	High	Low
Processing	Complex	Simple (binary)

ADC (Analog-to-Digital Conversion)

Process of converting a continuous analog signal to a discrete digital value.

Steps:

1. Sampling — measure analog value at fixed time intervals
2. Quantization — map each sample to nearest discrete level
3. Encoding — represent level as binary number

Sampling Rate

Term	Formula	Meaning
Sampling rate	fs = 1/T (Hz)	How many samples per second
Sampling period	T = 1/fs (seconds)	Time between samples

Example: T = 10 ms → fs = 1/0.010 = 100 Hz

Bit Resolution

Determines number of discrete values the ADC can represent.

Bits	Values (2^n)	Example
1	2	On/off
4	16
8	256	Standard audio
12	4096	Grove Base Hat ADC
16	65,536	CD audio

More bits = finer granularity = more accurate reading.

Bitrate

$\text{Bitrate}=f_s\times \text{bits per sample}$

Example: 44,100 Hz × 16 bits = 705,600 bits/second (CD audio)

Key Fact: Raspberry Pi Has NO Native ADC

The Raspberry Pi does NOT have a built-in ADC. All GPIO pins are digital only.

To read analog sensors, use the Grove Base Hat:

• 4 analog channels
• 12-bit resolution → values 0–4095
• Connected via 40-pin GPIO header (HAT = Hardware Attached on Top)

Grove Hat Analog Reading (Python)

import time
from grove.adc import ADC
 
adc = ADC()
channel = 0   # A0 connector
 
while True:
    value = adc.read(channel)   # 0–4095
    voltage = adc.read_voltage(channel)  # 0–3.3V
    print(f"ADC: {value}, Voltage: {voltage}V")
    time.sleep(1)

See Also

• ADC concept
• GPIO and reTerminal topic
• Electronics and Circuitry topic
• signals-digital-and-analog source