Running a Python script with exec node then parsing to javascript with function node in Node red

Question

I have a python script that controls a vibration sensor connected to my raspberry pi. I have that python script in the exec node. I need to parse the python code into javascript using the function node. (I'm doing this in node-red on the raspberry pi).

The JavaScript code I'm running does not return the value I need from the python code. I need the variable "sensor" to return in the javascript code.

python code:

import time 
import RPi.GPIO as GPIO

vibe = 4

GPIO.setmode(GPIO.BCM)
GPIO.setup(vibe, GPIO.IN)

def callback(Vibe):
    if GPIO.input(vibe):
        sensor = "vibration"
        print(sensor)

    else:
        print("error")

GPIO.add_event_detect(vibe, GPIO.BOTH, bouncetime=300)
GPIO.add_event_callback(vibe, callback)

while True:
    time.sleep(1)

GPIO.cleanup()

javascript code:

var vibrationSensor = msg.payload;

var sensor = str.substr(1,15);

msg.payload = {

    "vibration": sensor,

};

return msg;

What it looks like in node-red:

Could you please indent the code parts of the question correctly, highlighting the code, thus making it easier to read. — Atle Kristiansen
– Atle Kristiansen, Commented Aug 14, 2019 at 2:31
Possible duplicate of how to import printed C console to node red — hardillb
– hardillb, Commented Aug 14, 2019 at 6:40
Also your function node javascript doesn't do anything, there is no str to run the substring() function on — hardillb
– hardillb, Commented Aug 14, 2019 at 21:21

hardillb · Accepted Answer · 2019-08-14 06:38:55Z

1

Since the python code will never exit, you need to use the Daemon node rather than the exec node

answered Aug 14, 2019 at 6:38

hardillb

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4 Comments

pi_hobbyist Over a year ago

I used the Daemon node as suggested but I can't seem to get the node to work. In the Daemon node under Command i put: /usr/bin/sudo. Under Arguments i put: /home/pi/Desktop/vibe2.py. I also tried under Command: /usr/bin/sudo and Arguments: /usr/bin/python /home/pi/Desktop/vibe2.py.

hardillb Over a year ago

Have you checked both the node red logs and attached debug nodes to the other outputs of the node to get the errors and return value?

hardillb Over a year ago

You probably also need to make sure python is not buffering it's output to stdout.

hardillb Over a year ago

@pi_hobbyist try adding flush=True to your print() calls. e.g. print(sensor, flush=True)

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