APC_Australia_Issue_442_June_2017

The Serial Monitor will
output the current UTC
(GMT) 24-hour time.
Enter the URL for the
ESP8266 info into the
IDE’s Preferences page.
Arduino board listed), click on that
entry and choose ‘Boards Manager’
from the pop-up menu. Type ‘ESP8266’
into the search box of the new ‘Boards
Manager’ window and look for the
‘esp2866 by ESP8266 Community’ entry.
Move your mouse over the entry and
click on the Install button. When you’re
done, click Close.
At this point, you’ll need to close down
all open copies of the Arduino IDE and
restart it (this is so the new library can
be included).
NETWORK TIME PROTOCOL
If you wanted to know the time back in
pre-PC days, you’d dial ‘1194’ and hear
‘George the talking clock’ tell you,
‘at the third stroke, it will be three,
forty-seven and twenty seconds – beep,
beep, beep’. Today, there are few IT
systems that don’t require the ability
to timestamp and while computer
systems might not dial ‘1194’, they’re
very likely doing the 21st century
digital equivalent.
Network Time Protocol (NTP) is a
network standard used to synchronise
the clocks of computer devices to within
milliseconds and it works a little like
‘George’ using a ‘client/server’ model.
Your device is the ‘client’ and sends a
request to an NTP ‘server’ for the time,
the server sends the information back
in Coordinated Universal Time (UTC)
format, or what you might recognise as
‘Greenwich mean-time’ (GMT).
NTP is now a worldwide project where
several thousand servers are set up to
provide a free service of telling the
current UTC time. They’re grouped into
‘pools’ allowing load-sharing, so that no
one server cops the brunt of every
device requesting time data. Australia
has its own NTP pool at ‘au.pool.ntp.org’
— but head there with your browser and
you’ll just be redirected (eventually) to
the ntp.org project website. To get the
actual time in a more efficient manner,
we need an NTP client.
The Wi-Fi Internet
Clock we’ll finish
building next month.
MAKING AN NTP CLIENT
An NTP client sends of a formatted
request to an NTP server via the User
Datagram Protocol (UDP), which sends
back a 48-byte datagram with the UTC
time embedded. You can get started
with your NodeMCU dev board quickly
by using the existing ‘NTPClient’ file
you’ll find in the Arduino IDE — no
electronics required: just plug the USB
cable into the NodeMCU board. From
the IDE menu, select File > Examples,
scroll down to ‘ESP8266WiFi’ and load
up the ‘NTPClient’ app.
This app is great for testing your
NodeMCU board as there’s only one
thing you need to do, and that’s enter
the SSID and password of your wireless
network into the source code. After
that, you’re ready to flash it to the board.
Just plug the board into your PC or
laptop via a USB port with a microUSB
cable and again from the menu, select
Tools > Boards, scroll down and select
‘NodeMCU 1.0 (ESP-12E module)’.
Now again, choose Tools > Port and
select the ‘COMx’ option that isn’t
‘COM1’ (that’s your mouse). If you have
more than two COM options, remove
any other Arduino device you may
have connected.
With the board connected and
selected, upload the code to the board by
choosing from the menu Sketch >
Upload and watch the blue LED flash
on your NodeMCU board while the code
uploads.
At the top-right of your IDE, there’s
a small green ‘magnifying glass’ icon —
that launches the Serial Monitor.
Click it and the ‘COMx’ window should
launch. At the bottom-right of the
window, there’s a drop-down box
setting the Baud data transfer rate —
set this to ‘115200’. Give the board a few
seconds and it should begin to detail its
activities, including printing the
current UTC time even 10 seconds.
NEXT TIME...
We reckon there are some issues with
this code — for starters, the NodeMCU
Wi-Fi modem is powered up
continuously and the code hits the NTP
pool every 10 seconds: and no matter
where you are, the NTP time always
comes back as UTC time.
But with a little extra work, we can
convert UTC time into your local time
zone, add a small OLED display, reduce
the power consumption and create an
auto-set Wi-Fi internet clock.
We’ll cover how next month.
www.apcmag.com 105