9

Upgrade your humble letterbox with push notifications

FORGE

Next, click back to go to the APIs & Services

dashboard and click the Credentials item on the left-

hand menu. Here, click the ‘Create credentials’ button

and select ‘Service account key’. On the next screen,

‘New service account’ will be selected; give it a name

such as ‘postman-log’. Under ‘role’ select Project,

then Owner, leave the key type as JSON, and finally

click Create.

This will create and download a credentials file

to your computer. Save this to the Pi user’s home

directory as service_file.json, or if you are doing this

from another computer, use something like WinSCP to

copy this JSON file to the Pi.

Now that your app on the Google Cloud Platform

has the ability to work with Sheets in your Drive, it

needs to be granted specific permission to access

the Letterbox Activations spreadsheet. Open up the

JSON credentials file and look for the line which starts

‘client_email’; after that will be a long email address.

Copy the email address (without the quotes), return

to your Google Sheet and click the SHARE button in

the top-right of the browser window. Paste the email

address from before into the People field, ensure ‘Can

edit’ is selected and press the Send button. Press Yes

to any ‘Are you sure?’ style warnings – this enables

the app we’ve just created to make changes to the

spreadsheet, which is what we want.

Next, use PuTTY to connect to your Pi from another

computer on your network, using the IP address we

determined earlier, which will usually be something

similar to 192.168.0.xxx.

The project uses the pygsheets library to make

working with Google Sheets easier. Install pygsheets

with the following command:

Left

The notification, as

it appears on your

phone each time

the letterbox flap

is opened

You can test it out by

manually adding a new row

to the spreadsheet; wait

around a minute and a push

notification should pop up

on your phone

”

”

Above

The applet you create on IFTTT monitors your Google Sheet for

new rows being added, and sends a push notification to your

phone when it spots that the post has arrived

Below

Install the IFTTT app

on your smartphone,

and log in with the

same account in

order to receive the

push notifications