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,
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.
- 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?
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.
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.
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。）
Pictures showing how Rpi PWM GPIO can move servo motors
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. >>> >>> '''
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
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