Analog to Digital Signal

What it is

A comparator between two blocks. An analog block, such as a TK08 potentiometer or a TK20 light sensor, plugs into the IN socket at the top. Your board wires to the OUT header at the bottom. Between them, an LM393 compares the block's voltage with the one set by the blue knob and says which is higher, as HIGH or LOW on DIG.

The name promises an analog-to-digital converter, and it is one only in the narrowest sense: it turns a voltage into one bit. analogRead returns a number; this returns yes or no. So the block also passes the input's voltage through on ANA, and your board can read both: the decision from DIG, the number from ANA.

The page this replaces got several things wrong. ANA is not an input to connect a sensor to; the sensor goes in IN. DIG is not always HIGH above the threshold; the slide switch decides. The inputs do not work all the way to VCC. And the output does not give a clean edge by itself: with no hysteresis, a slow input makes it chatter.

The four things to know

The switch. H: DIG is HIGH while the input is higher than the knob. L: while it is lower.

The light. The red LED lights while DIG is LOW, the opposite of the output.

The range. The LM393 compares from 0 V to about VCC − 1.5 V. From 3V3 that is 1.8 V, and the top 45 % of the knob is out of range. The input may go higher, as long as the knob stays inside.

No hysteresis. Near the threshold a slow input makes DIG flicker. Read ANA and switch at two lines in the sketch.

Which pin is which

OUT, parts up, reading left to right. The names are printed along the pins:

IN takes a TinkerBlock sensor in its own order, GND, VCC, NC, SIGNAL, and prints no names. Its third position is connected to nothing, and DIG sits where a block's NC would be.

Wiring, in four lines

1. GND to your board's GND.
2. VCC to 5V on an Uno, 3V3 on an ESP32, ESP32-S3 or Pico. DIG is pulled up to VCC, so it must match.
3. DIG to a digital pin: D2 on an Uno, GPIO 25 on an ESP32, GPIO 7 on an ESP32-S3, GP15 on a Pico.
4. ANA to an analog pin if you want the number: A0 on an Uno, GPIO 34 on an ESP32, GPIO 4 on an ESP32-S3, GP26 on a Pico.

Then push an analog block into IN.

Example

// DIG_PIN, then ANA_PIN.
// Uno: 2 and A0. ESP32: 25 and 34. ESP32-S3: 7 and 4. Pico: 15 and 26.
const int DIG_PIN = 2;
const int ANA_PIN = A0;

void setup() {
  Serial.begin(115200);
  pinMode(DIG_PIN, INPUT);          // the block has its own pull-up
}

void loop() {
  Serial.print("DIG ");
  Serial.print(digitalRead(DIG_PIN));   // the decision
  Serial.print("   ANA ");
  Serial.println(analogRead(ANA_PIN));  // the number behind it
  delay(250);
}

import sys
import time
from machine import ADC, Pin

# DIG_PIN, then ANA_PIN.
# ESP32: 25 and 34. ESP32-S3: 7 and 4. Pico: 15 and 26.
dig = Pin(7, Pin.IN)              # no pull: the block has its own
adc = ADC(Pin(4))
if sys.platform == "esp32":
    adc.atten(ADC.ATTN_11DB)      # the full range, to about 3.1 V

while True:
    print("DIG", dig.value(), "  ANA", adc.read_u16())
    time.sleep_ms(250)

Where to start

The handbook below is eleven short articles, each with a working figure. The first read is the whole build: a TK08 in IN, four wires, and DIG and ANA side by side. H and L explains the switch.

For a lamp that comes on at dusk, a light switch puts a TK20 in the socket. If DIG flickers, read chatter and hysteresis; if the knob seems dead past halfway, the input range.