I'm working with face tracking and I want to activate some servomotors depending the motion of my face. For facetracking I'm using, an usb cam, opencv and dlib.
Now results the raspberry can't run my code in real time, it's to much for it. Probably is a very stupid question, but, can I run my program in my computer and pass the data to the raspberry in real time, and with the raspberry read this data and use the gpios to activate the servos?
Thank you very much
The pigpio library lets you control the GPIO of one or more networked Pis from a laptop. The laptop may be Windows, Mac, Android, or Linux based - in fact it can run any operating system as long as it can run Python. The pigpio Python module allows control of the remote GPIO.
pigpio will let you properly control servos. It provides hardware timed PWM (suitable for servos) on all the GPIO.
The Raspberry Pi foundation gpiozero supports pigpio as a back end and thus allows networked GPIO control.
Question
Face tracking using laptop usb cam, opencv and dlib
Face motion signal from laptop to Rpi to use GPIO to move servo motors.
Is this config OK?
Answer
I think it is a good use of laptop and Rpi. To know more about how to use Rpi's PWM GPIO pins to move servo motors, you might like to read my answer in the following post.
Using Rpi PWM GPIO pin to move servo motors
Swing Servo Youtube - tlfong01 2019may1201
And since the more powerful Rpi4 is coming soon, it is time to plan doing both jobs in Rpi4, saving your laptop for other R&D work.
Update 2019jun07hkt1241
The toy servo I used above as an example is not a good choice, because its positioning is not that precise and stable, not to mention is it is slow, and span limited (about 180 degrees), and has dead bands, ... For more advanced applications, I would recommend cheapy stepping motors and BLDC (BrushLess Direct Current) motors (with and without Hall effect quadrature position encoders) (references to add later). But for rapid prototyping, toy servos are very good。）
References
Pictures showing how Rpi PWM GPIO can move servo motors
Demo Programs
(1) Demo program
Fully debugged python programs (1) to move motor and (2) display PWM signal, with sample outputs
# Servo_test32 tlfong01 2019may12hkt1506 ***
# Raspbian stretch 2019apr08, Python 3.5.3
import RPi.GPIO as GPIO
from time import sleep
# *** GPIO Housekeeping Functions ***
def setupGpio():
GPIO.setmode(GPIO.BCM)
GPIO.setwarnings(False)
return
def cleanupGpio():
GPIO.cleanup()
return
# *** GPIO Input/Output Mode Setup and High/Low Level Output ***
def setGpioPinLowLevel(gpioPinNum):
lowLevel = 0
GPIO.output(gpioPinNum, lowLevel)
return
def setGpioPinHighLevel(gpioPinNum):
highLevel = 1
GPIO.output(gpioPinNum, highLevel)
return
def setGpioPinOutputMode(gpioPinNum):
GPIO.setup(gpioPinNum, GPIO.OUT)
setGpioPinLowLevel(gpioPinNum)
return
# *** GPIO PWM Mode Setup and PWM Output ***
def setGpioPinPwmMode(gpioPinNum, frequency):
pwmPinObject = GPIO.PWM(gpioPinNum, frequency)
return pwmPinObject
def pwmPinChangeFrequency(pwmPinObject, frequency):
pwmPinObject.ChangeFrequency(frequency)
return
def pwmPinChangeDutyCycle(pwmPinObject, dutyCycle):
pwmPinObject.ChangeDutyCycle(dutyCycle)
return
def pwmPinStart(pwmPinObject):
initDutyCycle = 50
pwmPinObject.start(initDutyCycle)
return
def pwmPinStop(pwmPinObject):
pwmPinObject.stop()
return
# *** Test Functions ***
def setHighLevelGpioPin18():
print(' Begin setHighLevelGpioPin18, ...')
gpioPinNum = 18
sleepSeconds = 2
setupGpio()
setGpioPinOutputMode(gpioPinNum)
setGpioPinHighLevel(gpioPinNum)
sleep(sleepSeconds)
cleanupGpio()
print(' End setHighLevelGpioPin18, ...\r\n')
return
def setPwmModeGpioPin18():
print(' Begin setPwmModeGpioPin18, ...')
gpioPinNum = 18
sleepSeconds = 10
frequency = 1000
dutyCycle = 50
setupGpio()
setGpioPinOutputMode(gpioPinNum)
pwmPinObject = setGpioPinPwmMode(gpioPinNum, frequency)
pwmPinStart(pwmPinObject)
pwmPinChangeFrequency(pwmPinObject, frequency)
pwmPinChangeDutyCycle(pwmPinObject, dutyCycle)
sleep(sleepSeconds)
pwmPinObject.stop()
cleanupGpio()
print(' End setPwmModeGpioPin18, ...\r\n')
return
# *** Main ***
print('Begin testing, ...\r\n')
setHighLevelGpioPin18()
setPwmModeGpioPin18()
print('End testing.')
# *** End of program ***
'''
Sample Output - 2019may12hkt1319
>>>
RESTART: /home/pi/Python Programs/Python_Programs/test1198/servo_test31_2019may1201.py
Begin testing, ...
Begin setHighLevelGpioPin18, ...
End setHighLevelGpioPin18, ...
Begin setPwmModeGpioPin18, ...
End setPwmModeGpioPin18, ...
End testing.
>>>
>>>
'''
(2) Program to display PWM wavefrom on scope
To display PWM waveform
def servoPwmBasicTimingTestGpioPin18():
print(' Begin servoPwmBasicTimingTestGpioPin18, ...')
gpioPinNum = 18
sleepSeconds = 120
frequency = 50
dutyCycle = 7
setupGpio()
setGpioPinOutputMode(gpioPinNum)
pwmPinObject = setGpioPinPwmMode(gpioPinNum, frequency)
pwmPinStart(pwmPinObject)
pwmPinChangeFrequency(pwmPinObject, frequency)
pwmPinChangeDutyCycle(pwmPinObject, dutyCycle)
sleep(sleepSeconds)
pwmPinObject.stop()
cleanupGpio()
print(' End servoPwmBasicTimingTestGpioPin18, ...\r\n')
return
References
(1) Raspberry Pi Servo Motor control - Rpi Tutorials
(2) Servo MG996R Datasheet - TowerPro
(3) Python (RPi.GPIO) API - SparkFun
(4) Using PWM in RPi.GPIO - SourceForge
(5) Raspberry Pi PWM Generation using Python and C - ElectronicWing
(8) UniPolar/Bipolar Stepping Motor 28byj48 Using L297D
(10) TowerPro SG5010 360 Degrees Servo
(11) Servo Basics and Control Function Discussion
