lms-esp32-pybricks-info

Using the GY-33 color sensor with the LMS-ESP32 board from Antons Mindstorms and LEGO® Spike running Pybricks

The TCS3472 based color sensor GY-33 comes only with minimal public documentation, luckily QuirkyCort created the micropython-gy33 library from some chinese documentation.

LMS-ESP32 code:

from pupremote import PUPRemoteSensor
from machine import Pin, UART
from neopixel import NeoPixel
from gy33_uart import GY33_UART # copy from https://github.com/QuirkyCort/micropython-gy33/blob/main/gy33-uart/gy33_uart.py

np = NeoPixel(Pin(25), 1) # onboard neopixel
np[0] = (255, 255, 0); np.write() # yellow = int

# connect GY-33 DR pin to LMS-ESP32 tx, CT pin to rx, VCC to 5V or 3.3V
gy33 = GY33_UART(UART(1, baudrate=115200, rx=Pin(20), tx=Pin(19))) # or pin 4,5 or ...
# initially connect with baudrate=9600 and execute gy33.set_baudrate(115200) once. 
# this switches the baud rate _permanently_ to 115k2 on next power on
#gy33.set_baudrate(115200)
gy33.set_integration_time(100) # raw values are proportional to integration time
gy33.set_output(raw=True, lcc=False, processed=False) # speed up by disabling other responses
gy33.set_led(10)
if not gy33.update(wait=1000): # connection check
    np[0] = (255, 0, 0); np.write() # red = error
    raise RuntimeError('gy33 not responding')

def gyGet():
    return tuple(gy33.get_raw())

def gyLed(v):
    gy33.set_led(v)

def gyTim(v):
    gy33.set_integration_time(v)

rs = PUPRemoteSensor(power=True)
rs.add_command('gyGet', 'HHHH') # values 0~6000
rs.add_command('gyLed', '', 'B') # value 0-10
rs.add_command('gyTim', '', 'B') # value 24,100,...

np[0] = (0, 0, 255); np.write() # blue = wait for spike
rs.process()

np[0] = (0, 255, 0); np.write() # green = ready
while True:
    rs.process()
    gy33.update() # read raw value

Pybricks code:

from pybricks.pupdevices import ColorSensor
from pybricks.parameters import Port
from pybricks.tools import wait, StopWatch
from pupremote_hub import PUPRemoteHub # copy from https://github.com/antonvh/PUPRemote/blob/main/src/pupremote_hub.py
import gy33_color # copy from example folder

sw = StopWatch()
cs = ColorSensor(Port.F)
rh = PUPRemoteHub(Port.E)
rh.add_command('gyGet', 'HHHH')
rh.add_command('gyLed', '', 'B')
rh.add_command('gyTim', '', 'B')
rh.call('gyLed', 10)

while True:
    gyRaw = rh.call('gyGet') # GY-33 color sensor
    csHsv = cs.hsv()         # Lego color sensor
    csCol = cs.color()
    gyHsv = gy33_color.rgbc_to_hsv_Color(*gyRaw)
    gyCol = gy33_color.hsv_to_standard_Color(gyHsv)
    print(sw.time(), csHsv, csCol, '--', gyRaw, gyHsv, gyCol, sep=', ')

and create gy33_color.py with content from this repo.

Mounting the GY-33

t.b.d.

Comparison

• The GY-33 automatically sends new values over the serial line after the integration time. Reasonable integration times are 100 and 24msec. Reading more frequently from Spike side does not make sense.
• The GY-33 supports UART and I2C communication modes. I2C mode has faster transfer speed, but each get_raw() includes a communication roundtrip. Only serial mode can change the integration time and has automatic sending of new values.
• The Lego sensor returns a new value each 9~10msec.
• The Lego sensor is best places 1 beam from the ground, the GY33 sensor nearest to ground as possible.
• With the lens mount the GY-33 is protected against ambient light, for other TCS3472 based sensors you would have to 3D print yourself.
• the sharpness off black & white separation is comparable. I would have expected a significant advantage for the Lego sensor due to its integrated optics and the LEDs outside the optics. Values look better but not significant: .

Todo

• Compare linefollower with both sensors and different integration time
• The code above uses the library from QuirkyCort. This first communicates with the microcontroller on the back of the board which then communicates with the TCS3472. Could try the other pins to directly communicate with the TCS3472 with a different library