GadgetData

I am setting up a Raspberry Pi (call it "the gadget") that will read Property:GadgetTestProperty encoded on this page. If the value is between 0 and 10 it will drive a servo in a specific way.

Setting the value

Setting Property:GadgetTestProperty to 6

• SMW could encode more, but for now let's have one so my gadget doesn't have to error check.

API code to read the value

The following will query what the value of Property:GadgetTestProperty for this page:

• https://sandbox.semantic-mediawiki.org/w/api.php?action=ask&query=[[GadgetData]]|?GadgetTestProperty&format=json

The following will return all properties for this page:

• https://sandbox.semantic-mediawiki.org/w/api.php?action=browsebysubject&subject=GadgetData&format=json

Python code that reads the value and moves servo

import pigpio
import time
import json
import requests #used to grab the data at the URL
import time #for sleeping

respURL = "https://sandbox.semantic-mediawiki.org/w/api.php?action=ask&query=[[GadgetData]]|?GadgetTestProperty&format=json"
pollDelay = 10	# the delay in s between polls of respURL
timeOneUnit = 1	# time it takes to travel DOWN one unit of time - empirical
upRatio = 1.28	# the ratio of time it takes to go up rather than down - empirical
tapeMax = 6.5	# 6.5s goes to not quite the max of red tape
dataMax = 10	# show value between 0 and this, ie divide the tapeMax by this to get the distance/time per unit

	
def tapeHold():
	print("tapeHold")
	pi.hardware_PWM(18,47,71000) # parameters are a mix between spec and empirical

def tapeUp(howMuch):
	print("tapeUp by " + str(howMuch))
	pi.hardware_PWM(18,47,61000) # parameters are a mix between spec and empirical
	time.sleep(howMuch * tapeMax/dataMax * upRatio)
	tapeHold()
	
def tapeDown(howMuch):
	print("tapeDown by " + str(howMuch))
	pi.hardware_PWM(18,46,78300) # parameters are a mix between spec and empirical
	time.sleep(howMuch * tapeMax/dataMax)
	tapeHold()
  
# initialize
pi = pigpio.pi()
curr = 0
newVal = 0

while True:
	response = requests.get(respURL)
	AllData = (response.text)
	JSONData = json.loads(AllData)
	KeyValue = (JSONData["query"]["results"]["GadgetData"]["printouts"]["GadgetTestProperty"])
	if str(KeyValue) == "[]": # that's what we get when there is no value or an out of range value
		print ("Not getting good data from page, assuming current value stays")
		newVal = curr
	else:
		newVal = (KeyValue[0])

	if newVal == curr:
		print("same")
	elif newVal > curr:
		tapeUp(newVal-curr)
		curr = newVal
	elif newVal < curr:
		tapeDown(curr-newVal)
		curr = newVal
	else:
		print("this should never happen")

	time.sleep(pollDelay)