Step 3 (optional): Working with an offline fallback

Designing with incoming live data is exciting, however it also makes our design susceptible for failures. What if the internet connection is disturbed? What if the server stops sending?

It can also happen that something goes wrong during our workshop, or that you have issues with connecting your ItsyBitsy to the internet. For this case, we created some offline fallbacks that allow you to learn how to embody data even if you do not manage to connect, or if you do this workshop at a different time.

ISS Distance and Perlin Noise Fallback

We saved some real data for the ISS and Perlin noise in these .txt files. This allows you to loop through the file and read the data as if it was coming from our MQTT server.

Download these two files by right-clicking and selecting "Download linked file" (or the equivalent of your browser):

Perlin_data.txt

ISS_distance.txt
Add the files Perlin_data.txt and ISS_distance.txt to your CIRCUITPY device.

Create a new file called offline_data_handler.py , paste the code below into the file and save it on your CIRCUITPY device.

import storage
import time
import random

## --- Variables 
interval = 1.0 # time between data points in seconds

## Choose only one file at a time
datasource = "ISS_distance.txt"
#datasource = "Perlin_data.txt"

last_check_time = 0.0

file = open(datasource, "r")
data = file.readlines()
file.close()
line_number = random.randint(0,len(data))

datapoint = 0

# We will use this value to save new incoming data
incoming_value = 0

## --- Functions

def get_data_point():
   global datapoint
   global last_check_time
   global data
   global line_number
   current_time = time.monotonic()

   if current_time > last_check_time + float(interval):
      line_number = line_number + 1
      datapoint = data[line_number]

   if line_number >= len(data) - 1 :
      line_number = 0

   return datapoint
      

# --- Main loop
while True:
   time.sleep(interval)
      
   incoming_value = get_data_point()
   print(incoming_value)

Add the following line to your code.py file and save it.
```
import offline_data_handler
```
Open the Serial Monitor and you should see the collected data!

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