DE2120 Barcode Scanner – Scanning Examples (MicroPython)

Basic scan

This example initializes the DE2120 scanner and reads barcodes in manual trigger mode — the scanner outputs data each time the physical button on the breakout board is pressed, or when a scan is triggered via software.

from machine import UART
from de2120 import DE2120
import time

# Adjust tx and rx to match the pins you have wired on your board
scanner = DE2120(tx=5, rx=4)

if not scanner.begin():
    print("DE2120 not detected. Check wiring.")
    raise SystemExit

print("DE2120 ready. Press the button on the scanner to read a barcode.")

while True:
    barcode = scanner.readBarcode()
    if barcode:
        print("Scanned:", barcode)
    time.sleep_ms(20)

Function reference

DE2120(tx, rx, uart_id=1)

Creates a DE2120 scanner object using the specified TX and RX pin numbers. A UART peripheral is created internally at 9600 baud. You can also pass a pre-built UART object via the uart parameter instead.

Returns value: DE2120 object

Function parameters:

Type	Name	Description
int	tx	GPIO pin number for UART TX (MCU → scanner).
int	rx	GPIO pin number for UART RX (scanner → MCU).
int	uart_id	UART peripheral ID (default: 1).

scanner.begin()

Verifies communication with the scanner. Automatically detects and negotiates the baud rate down to 9600 bps if needed. Clears any pending data from the receive buffer before returning.

Returns value: bool — True if the scanner responded correctly, False if not detected.

scanner.readBarcode()

Polls the UART receive buffer for barcode data. Call this repeatedly in a loop. When a complete CR-terminated barcode string arrives, it is returned as a string. Returns None if no complete barcode is available yet.

Returns value: str — The decoded barcode string, or None if no scan is ready.

Full example

de2120-readBarcode.py

Basic barcode reading example using manual trigger mode

---

Continuous read mode

In continuous mode the scanner reads automatically without needing any trigger command. This is useful for checkout-style applications where items are passed in front of the scanner.

from machine import UART
from de2120 import DE2120
import time

scanner = DE2120(tx=5, rx=4)

if not scanner.begin():
    print("DE2120 not detected. Check wiring.")
    raise SystemExit

# Enable continuous read with a 0.5 s repeat interval for duplicate barcodes
scanner.enableContinuousRead(repeat_interval=2)

print("DE2120 in continuous read mode. Point at a barcode.")

while True:
    barcode = scanner.readBarcode()
    if barcode:
        print("Scanned:", barcode)
    time.sleep_ms(50)

Function reference

scanner.enableContinuousRead(repeat_interval=2)

Switches the scanner to continuous scanning mode. The repeat_interval controls how duplicate barcodes are handled.

Returns value: bool — True on success.

Function parameters:

Type	Name	Description
int	repeat_interval	0 = output once per barcode, 1 = continuous with no delay, 2 = 0.5 s delay between duplicates (default), 3 = 1 s delay.

scanner.disableContinuousRead()

Returns the scanner to manual (trigger) mode.

Returns value: bool — True on success.

scanner.enableMotionSense(sensitivity=50)

Enables motion-triggered scanning. The scanner activates automatically when movement is detected in front of it.

Returns value: bool — True on success.

Function parameters:

Type	Name	Description
int	sensitivity	Motion sensitivity: 15 = highest sensitivity, 20 = high, 30, 50 (default), 100 = lowest.

scanner.disableMotionSense()

Disables motion sensing and returns to manual mode.

Returns value: bool — True on success.

Full example

de2120-continuousRead.py

Continuous barcode scanning mode example

---

Configuring the scanner

This example shows how to send configuration commands to the scanner at runtime. It toggles Code ID — a prefix character the scanner prepends to every scan to identify the barcode type (e.g. A for Code 128, Q for QR Code).

import sys
import uselect
from de2120 import DE2120
import time

scanner = DE2120(tx=5, rx=4)

if not scanner.begin():
    print("Scanner did not respond. Check wiring.")
    raise SystemExit

print("Scanner online!")

poll = uselect.poll()
poll.register(sys.stdin, uselect.POLLIN)

def stdin_available():
    return bool(poll.poll(0))

def flush_stdin():
    while stdin_available():
        sys.stdin.read(1)

while True:
    flush_stdin()
    print()
    print("Transmit Code ID with barcode? (y/n)")

    while not stdin_available():
        barcode = scanner.readBarcode()
        if barcode:
            print("Code found:", barcode)
        time.sleep_ms(200)

    cmd = sys.stdin.read(1)
    if cmd == 'y':
        print("Code ID enabled")
        scanner.sendCommand("CIDENA", "1")
    elif cmd == 'n':
        print("Code ID disabled")
        scanner.sendCommand("CIDENA", "0")
    else:
        print("Command not recognized")

Function reference

scanner.sendCommand(cmd, arg="", max_wait_ms=3000)

Sends an arbitrary configuration command to the scanner. The library wraps it in the required protocol format (^_^COMMAND<ARG>.) automatically. Waits up to max_wait_ms milliseconds for an ACK or NACK response.

Returns value: bool — True if the scanner acknowledged (ACK), False on NACK or timeout.

Function parameters:

Type	Name	Description
str	cmd	Command string (e.g. "CIDENA").
str	arg	Optional argument string (e.g. "1" to enable).
int	max_wait_ms	Maximum wait time in milliseconds (default: 3000).

scanner.lightOn()

Turns on the white illumination LEDs.

Returns value: bool — True on success.

scanner.lightOff()

Turns off the white illumination LEDs.

Returns value: bool — True on success.

scanner.reticleOn()

Turns on the red aiming reticle LED.

Returns value: bool — True on success.

scanner.reticleOff()

Turns off the red aiming reticle LED.

Returns value: bool — True on success.

scanner.enableAll1D()

Enables all supported 1D barcode symbologies.

Returns value: bool — True on success.

scanner.disableAll1D()

Disables all 1D barcode symbologies.

Returns value: bool — True on success.

scanner.enableAll2D()

Enables all supported 2D barcode symbologies.

Returns value: bool — True on success.

scanner.disableAll2D()

Disables all 2D barcode symbologies.

Returns value: bool — True on success.

scanner.changeReadingArea(percent)

Sets the percentage of the camera frame used for barcode detection. Narrowing the area can speed up decoding in controlled environments.

Returns value: bool — True on success.

Function parameters:

Type	Name	Description
int	percent	Frame percentage: 100 (full, default), 80, 60, 40, or 20 (center region only).

scanner.factoryDefault()

Resets all scanner settings to factory defaults. Note: the scanner temporarily disconnects from serial while restarting.

Returns value: bool — True on success.

Full example

de2120-sendCommand.py

Example showing how to send configuration commands to the DE2120 scanner at runtime

ℹ️

For a full interactive menu covering all scanner settings (flashlight, reticle, reading area, scanning mode, and symbologies), see the de2120-serialSettings.py example:

de2120-serialSettings.py

Full interactive configuration menu for the DE2120 scanner