Making a Barcode Scan Robot with Lego Boost and Webcam
If you want to quickly create a walking robot, you can use the Lego Boost. In this post, I will share how to use a webcam, Lego Boost, and Dynamsoft Barcode Reader SDK to make a robot for scanning barcodes. The programming language used in this article is Python.
What You Should Know
How to Build the Robot with Lego Boost
To build the robot, install the Boost app and follow the relevant tutorials.
Python Programming Requirements
- Download Dynamsoft Barcode Reader for Linux. After extracting the package, copy libDynamsoftBarcodeReader.so to /usr/lib.
- Get a free 30-day trial license of Dynamsoft Barcode SDK.
- Get the source code of Dynamsoft Python barcode module and follow the steps to build and install.
- Install one of the Bluetooth backends:
pip install pygatt
pip install gatt
pip install gattlib
pip install bluepy
- Install pylgbst to interact with Lego Boost Move Hub:
pip install https://github.com/undera/pylgbst/archive/1.0.tar.gz
- Install OpenCV Python:
pip install opencv-python
# or
pip3 install opencv-python
How to Control Lego Boost Robot to Scan Barcodes
Create a camera view window using OpenCV:
vc = cv2.VideoCapture(0)
vc.set(3, 640) #set width
vc.set(4, 480) #set height
if vc.isOpened(): # try to get the first frame
rval, frame = vc.read()
else:
return
windowName = "Robot View"
try:
while True:
rval, frame = vc.read()
cv2.imshow(windowName, frame)
Due to GIL (Python Global Interpreter Lock), we need to run Bluetooth connection code and barcode decoding algorithm in another process rather than thread. All data, including key events, webcam frames, and barcode results, are transferred via Queue:
num = Value('i', 1)
result _queue = Queue(1)
key _queue = Queue(1)
frame _queue = Queue(1)
cond = Condition()
dbr _proc = Process(target=dbr _run, args=(
frame _queue, key _queue, cond, num, result _queue))
dbr _proc.start()
Here are the key definitions:
- a: left
- d: right
- w: up
- s: down
- q: terminate the app
- c: capture images and scan barcodes
The code for controlling the Lego Boost Robot is pretty simple. I use Gatt Backend:
conn GattConnection()
try:
conn.connect()
hub = MoveHub(conn)
print('Robot connected')
speed = 0.5
if key == ord('a'):
# left
hub.motor _AB.angled(90, speed * -1, speed)
elif key == ord('d'):
# right
hub.motor _AB.angled(90, speed, speed * -1)
elif key == ord('w'):
# up
hub.motor _AB.start _speed(speed)
elif key == ord('s'):
# down
hub.motor _AB.start _speed(speed * -1)
elif key == ord('p'):
hub.motor _AB.stop()
finally:
conn.disconnect()
Read the QR code and put the results into the queue:
dbr.initLicense('DLS2eyJoYW5kc2hha2VDb2RlIjoiMjAwMDAxLTE2NDk4Mjk3OTI2MzUiLCJvcmdhbml6YXRpb25JRCI6IjIwMDAwMSIsInNlc3Npb25QYXNzd29yZCI6IndTcGR6Vm05WDJrcEQ5YUoifQ==')
if key == ord('c'):
inputframe = frame _queue.get()
results = dbr.decodeBuffer(inputframe, 0x4000000)
if (len(results) > 0):
for result in results:
print("Type: " + result[0])
print("Value: " + result[1] + "\\n")
result _queue.put(Result(inputframe, results))
Draw the barcode position and decoded text result using OpenCV:
ret = result _queue.get _nowait()
results = ret.results
image = ret.image
thickness = 2
color = (0,255,0)
for result in results:
print("barcode format: " + result[0])
print("barcode value: " + result[1])
x1 = result[2]
y1 = result[3]
x2 = result[4]
y2 = result[5]
x3 = result[6]
y3 = result[7]
x4 = result[8]
y4 = result[9]
cv2.line(image, (x1, y1), (x2, y2), color, thickness)
cv2.line(image, (x2, y2), (x3, y3), color, thickness)
cv2.line(image, (x3, y3), (x4, y4), color, thickness)
cv2.line(image, (x4, y4), (x1, y1), color, thickness)
cv2.putText(image, result[1], (min([x1, x2, x3, x4]), min([y1, y2, y3, y4])), cv2.FONT _HERSHEY _SIMPLEX, 1, (0,0,255), thickness)
cv2.imshow("Localization", image)
Run the app:
python3 app.py
