1. Comments
This kit only has code examples for programming the Pi Pico in the Arduino environment. You are welcome to play around with this, but it hasn’t been tested. We will be programming the cars using MicroPython instead.
2. Build notes
The camp’s docs has information about all of the robots.
Open the main build and information document:
docs / Freenove 4WD / Mecanum_wheels / Tutorial.pdf
Survey the PDF’s bookmarks to get a sense of what’s in this document.
3. code
Test code for the RGB lights
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import time
from machine import Pin
led = Pin(25, Pin.OUT)
led.on()
time.sleep(1)
led.off()
time.sleep(1)
from neopixel import NeoPixel
np = NeoPixel(Pin(16, Pin.OUT), 8)
np[1] = (0, 0, 0)
np.write()
Motor utilities for demonstrations
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from machine import Pin
from machine import PWM
from machine import Timer
def duty_to_u16(x):
"""Convert a percentage 0..100 into the range used by the PWM hardware of
0..65535. (2**16 - 1), the largest unsigned 16-bit number.
The sign of _x_ is ignored and treated as always positive."""
x = abs(x) # ensure this is a positive number
out = (65535 * x) // 100
return out
class motor:
"""Class that describes how to control _some_ motor, since they all work
the same way. When creating a specific instance of the motor drive, it
needs to be told which two pins it has control over, labeled _a_ and _b_
here."""
#
# Initialization
#
def __init__(self, pin_a, pin_b, freq=1_000):
self.pin_a = pin_a
self.pin_b = pin_b
self.a = PWM(Pin(pin_a, Pin.OUT), freq=freq, duty_u16=0)
self.b = PWM(Pin(pin_b, Pin.OUT), freq=freq, duty_u16=0)
self._running = False
#
# Basic operations
#
def coast(self):
# see the DRV8837 motor driver chip datasheet
self.a.duty_u16(0) # always low
self.b.duty_u16(0)
self._running = False
def brake(self):
# see the DRV8837 motor driver chip datasheet
self.a.duty_u16(65535) # always high
self.b.duty_u16(65535)
self._running = False
def stop(self, arg=None):
"""There are two ways to "stop", so uncomment the one that best fits
your situation."""
self.coast()
#self.brake()
if arg:
arg.deinit()
#
# Actual motions.
#
# speed - percentage 0..100. Negative values mean opposite direction.
# howlong - time in seconds (currently ignored)
#
def forward(self, speed, howlong=None):
speed_u16 = duty_to_u16(speed)
self.a.duty_u16(speed_u16)
self.b.duty_u16(0)
self._running = True
if howlong:
t = Timer(mode=Timer.ONE_SHOT, period=howlong, callback=self.stop)
def backward(self, speed, howlong=None):
speed_u16 = duty_to_u16(speed)
self.a.duty_u16(0)
self.b.duty_u16(speed_u16)
self._running = True
if howlong:
t = Timer(mode=Timer.ONE_SHOT, period=howlong, callback=self.stop)
def go(self, speed, howlong=None):
"""Move forward or backwards according to the sign of speed."""
if speed > 0:
self.forward(speed, howlong)
elif speed < 0:
self.backward(-speed, howlong)
elif speed == 0:
self.stop()
else:
print(f"ERROR: Unknown speed: {speed}")
def is_running(self):
return self._running
# Replace the PINX and PINY with the pin numbers that match the wiring as shown
# in the "Pins of the Car" section in the documentation.
m1 = motor(19, 18)
m2 = motor(20, 21)
m3 = motor(6, 7)
m4 = motor(8, 9)
def stop():
m1.stop()
m2.stop()
m3.stop()
m4.stop()
def coast():
m1.coast()
m2.coast()
m3.coast()
m4.coast()
def brake():
m1.brake()
m2.brake()
m3.brake()
m4.brake()
def go(speed, howlong=None):
m1.go(speed, howlong)
m2.go(speed, howlong)
m3.go(speed, howlong)
m4.go(speed, howlong)