Photon Weather Shield Hookup Guide V11 Datasheet by SparkFun Electronics

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Page 1 of 15 Photon Weather
Photon Weather Shield Hookup Guide V11
Have you ever wanted to have your own weather station? Or how about
your own thermostat capable of controlling your home climate from the
Web? Using the Photon from Particle coupled with the Photon Weather
Shield from SparkFun, you can now connect your weather related project to
the Internet of Things!
Note: All SparkFun shields for the Photon are also compatible with the
(now retired) Core from Particle. The WKP, DAC and VBT pins on the
Photon will be labeled A7, A6 and 3V3*, respectively, on the Core, but
will not alter the functionality of any of the Shields.
Required Materials
If you are looking to just measure temperature, humidity, and/or
barometric pressure, you can integrate the Photon Weather Shield into
your project right out of the box! No soldering necessary!
SparkFun Photon Weather Shiel
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Photon Weather Shield Hookup SparkFun Wish List
The shield also has numerous optional ports on which other sensors can
be connected. Those optional devices will be discussed briefly in this
tutorial, but examples showing how to use those external peripherals will be
included in another tutorial, linked at the end of this one.
To follow along with this tutorial, you will need the following.
SparkFun Photon Weather Shield
The SparkFun Photon Weather Shield is an easy-to-use add-on boar…
Particle Photon (Headers)
Particle's IoT (Internet of Things) hardware development board, the P…
USB microB Cable - 6 Foot
USB 2.0 type A to micro USB 5-pin. This is a new, smaller connector f…
Suggested Reading
The following are suggestions for other resources to read before getting
started with your Photon Weather Shield.
If you have never worked with the Photon or the Core before, we
highly recommend visiting the getting started documentation
available on the Particle site.
We have also written a Photon Development Guide that goes over
three different methods for developing code for the Photon.
Check out the Hookup Guides for each of the sensors located on the shield
for more information specific to that sensor.
Si7021 Humidity and Temperature Sensor
Hookup Guid
AY 5, 2016
The Si7021 humidity and temperature sensor is an easy to use, digital, low-
cost sensor to aid you in all your environment sensing needs.
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If you are unfamiliar with any of the concepts below, we suggest checking
out those tutorials as well.
Hardware Overview
The Photon Weather Shield has a lot of functionality packed into one tiny
package. Let’s go over each section of the shield.
Photon Footprint
Both the Core and the Photon fit right onto the shield. Copper pours
underneath the antenna were restricted so as not to interfere with wireless
connections. Each pin is also broken out to the sides of the Photon for
accessibility. When attaching a Photon, be sure to line up the beveled end
of the Photon with the beveled silkscreen on the PCB.
MPL3115A2 Pressure Sensor Hookup Guid
Getting started with the MPL3115A2 Pressure Sensor.
Serial Communicatio
synchronous serial communication
concepts: packets, signal levels,
baud rates, UARTs and more!
Using GitHub
How to use repositories and GitHub
for version control.
n introduction to I2C, one of the
main embedded communications
protocols in use today.
Serial Terminal Basics
This tutorial will show you how to
communicate with your serial
devices using a variety of terminal
emulator applications.
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The simplest way to power the shield is to attach a Photon, and then power
the Photon through the micro USB connector. This will power the Photon as
well as all the components on the shield.
The downside to that power scheme is that micro USB connectors tend to
be fragile when put under a lot of mechanical stress, and they can rip right
off the PCB if pulled too hard. Thus, we provided a few other options for
power connectors.
On the underside of the shield, you’ll find a footprint for both an SMD Barrel
Jack and a 2-pin, 3.5mm screw terminal. Either of these can be soldered to
the PCB and used for alternate power inputs. The maximum voltage
supplied on these alternate connectors should not exceed 12V. For a
detailed explanation, read on.
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Powered through the Barrel Jack.
For the screw terminal, you can solder it to either side of the shield, since it
fits underneath the Photon. Be sure to keep track of which pin is (+) and
which is (-).
Powered through the Screw Terminal.
On-Board 3.3V Regulator and Power Solder
There is also a 3.3V regulator on the shield. If you are powering the Photon
through the micro USB connector, this regulator is bypassed. Powering
through one of the alternative power connectors mentioned above routes
power through the shield’s 3.3V regulator, which is then tied to the 3.3V
rail on the Photon, powering it as well.
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On-board 3.3V regulator and accompanying circuitry.
The main benefit to using the on-board regulator is that is has a higher
maximum voltage rating than the regulator located on the Photon. As stated
in the Photon datasheet, if power is supplied directly to the VIN pin on the
Photon, the voltage should be regulated between 3.6VDC and 5.5VDC. In
contrast, the MIC5219 regulator is rated for 2.5VDC to 12VDC, as per its
datasheet. Being able to power this system at 12V is handy for solar-
powered weather stations.
However, if you would rather have the alternative power source route power
through the regulator on the Photon (for lower current consumption during
sleep perhaps), simply cut the trace on the Power Select jumper (between
the VREG and RAW pads), and add a blob of solder between RAW and
P_VIN (Photon VIN) pads. Just be sure to not exceed voltages of 5.5-6V
once this alteration has been made.
Warning! Never power the Photon/Shield through both the micro USB
connector and the barrel jack or screw terminal at the same time! If
you need both connected for whatever reason (programming in DFU
mode over USB while powered via the barrel jack, for example), you’ll
need to cut the trace on the 3.3V Disable jumper, pictured below.
Only cut this trace is you have not altered the Power Select jumper
On-Board Sensors
The weather shield comes with two on-board sensors. Together, these two
sensors can give you a lot of information about the environmental
conditions around you or your project.
Si7021 or HTU21D Humidity and Temperature Sensor
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There are two versions of the Weather Shield, one containing the HTU21D
and one containing the Si7021-A10. The HTU21D can be found on older
versions of the Photon Weather Shield, while the Si7021 can be found on
the latest version of the shield, V11.
The Si7021 is functionally identical to the HTU21D, and they both share the
same register addresses and command codes. To make it easier on the
user, the Photon Weather Shield library automatically detects which sensor
is present on your board without needing a separate library. More on that
MPL3115A2 Barometric Pressure Sensor
The MPL3115A2 is a MEMS pressure sensor that provides Altitude data to
within 30cm. The sensor outputs are digitized by a high-resolution 24-bit
ADC and transmitted over I C. Pressure output can be resolved with output
in fractions of a Pascal, and Altitude can be resolved in fractions of a meter.
It provides 12-bit temperature measurements in degrees Celsius. This
sensor also communicates over I C and comes connected to the Photon’s
I C bus by default.
Optional Peripherals
Soil Moisture Sensor
For those who want to keep track of their houseplant conditions or for those
who want to know topsoil conditions in their gardens, the weather shield
has an optional port for a Soil Moisture Sensor.
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Leaving the soil moisture sensor powered all the time leads to corrosion of
the probes. To account for this, this port breaks out Digital Pin D5 as the
power pin for the sensor, allowing the Photon to power the sensor, take a
reading, and then disable power, giving the probes a longer lifespan. The
moisture level can be read on Analog Pin A1.
More information about the Soil Moisture sensor can be found in the
Hookup Guide.
Soil or Water Temperature Sensor
In addition to soil moisture, you can also add a waterproof temperature
sensor. Whether you have a pond you’d like to monitor near your weather
station or you want to know if the ground is still frozen or not, this can be a
great addition to any weather station.
The waterproof version of the DS18B20 temperature senor is a go-to option
for many users looking to sense the temperature of various environments
that may not be so kind to electronics.
A port for this sensor is broken out along with the necessary 4.7K pull-up
resistor located between the Vcc and Signal lines. The Signal line is
connected to Digital Pin D4. Communicate with this sensor using the
OneWire and Dallas Temperature libraries.
SparkFun Soil Moisture Sensor
Temperature Sensor - Waterproof (DS18B20
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IC Port
I C is becoming increasingly popular as a means by which to communicate
with sensors. Thus, it made sense to add an I C port to allow users to add
other sensors to their project. One great example would be adding an
external light sensor. Since most weather stations need to be enclosed in a
weatherproof housing, having a light sensor on-board didn’t make much
sense. However, adding the I C port allows one to connect sensors such as
the TSL2561 Luminosity Sensor or the ISL29125 RGB Light Sensor along
with a whole slew of other I C sensors.
I C Pull-ups
Many SparkFun I C Breakouts have solder jumpers for disabling the pull-up
resistors necessary on most I C designs. The Photon Weather Shield is no
different. If you already have a sensor that has pull-ups, you can disable
them on the shield by cutting the traces with a hobby knife. Or, if you would
rather leave the shield as is, you can disable the pull-ups on every I C you
add to the bus. The important thing to remember is that only one device on
the bus needs to have its pull-ups active. All others should be disabled.
Serial 1 Port
There is another port broken out, this time for the USART Serial 1 port on
the Photon. Serial ports are great for debugging. They also allow for various
other wireless technologies to be attached for mesh networking or for user
feedback via an LCD or other display. Let’s say you wanted additional
sensors around you home, well beyond the range of your WiFi signal. You
could attach an Xbee Explorer to the Serial 1 port on the Weather shield
and have your other node (consisting of a stand-alone XBee or an XBee
Arduino combo, for example) out in the field, feeding data back to the
Photon, which then sends the collective data to the web.
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Another use case is wanting to have your weather station outside while still
receiving data on a display indoors somewhere. This could easily be
accomplished by attaching a BlueSMiRF Bluetooth module to the Serial 1
port and having another BlueSMiRF attached to a Serial Graphic LCD
display installed in your home.
A SparkFun BlueSMiRF Silver connected to the Serial 1 Port using a 6-pin,
right-angle female header with the outermost pins removed.
The pins on the shield match up with any of our BlueSMiRF modules. For
other wireless solutions, you may have to wire each pin manually as they
may not match up exactly.
RJ-11 Weather Meter Connectors
If you would like to place your Weather Shield outdoors and create a fully-
functional weather station, you can grab a set of Weather Meters and
connect them to the RJ-11 connectors located on the Weather Shield. With
these meters attached, you can measure wind speed, wind direction and
Weather Meter
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Throw in a stand, and you have yourself the makings for a very powerful
weather station.
Particle IDE
If this is your first time using a Particle Photon, there are some extra steps
you’ll need to complete before you can follow the example in this tutorial.
First-time users will need to create a free account Once
your account is created, you’ll need to claim your Photon. Detailed
instructions on how to do this can be found on Particle’s website.
Once your account is created and your Photon is claimed, head back to, and log in.
Collecting Weather Data
If you have not done so already, attach your Photon to the Weather Shield,
and apply power through the Micro USB jack on the Photon, plugging the
other end of the USB cable into your computer. If you opted for one of the
alternate power schemes mentioned in the Hardware Overview section,
power your Photon and shield accordingly.
Your Photon’s RGB LED should be breathing cyan to indicate that you are
connected to the Internet and are ready to upload code.
To see data from the Weather Shield, you need to upload a sketch to the
Photon. Luckily, there’s a library with an example sketch to get you started
collecting weather data. To get to the example, click on the libraries button
in the Particle IDE.
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In the library search bar, type the word weather.
Click on the SparkFun_Photon_Weather_Shield_Library. You should see
the library files (.cpp and .h) listed. Below the Examples heading, you
should see a couple example .ino files. Click on the one that says
Once clicked, you should see a button that says “Use this Example”. You
should then see the sketch under the My apps heading.
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SPARKFUN‘PHOTON_WEAT HER_SHIELD>EXAMPLE BLINK AN LED Pamde Devxces (a 011mm Demo c > Page 13 of15
We now need to select the device to which to upload code. Clcik the
devices icon in the IDE.
If you have just one Photon claimed, it will be the only device to choose
from. If you have more than one Photon, you will need to select the star
next to the device you want to program.
With the example open, click the verify button to make sure the code
compiles correctly.
Once verified, click the upload button to program the Photon.
You should see the Photon’s RGB LED blink magenta for a few seconds
indicating it’s being programmed.
Firmware Updates: If this is the first time you've uploaded code to
this Photon or if you haven't used this Photon in awhile, it may go
through an automatic firmware update. These typically take less than
a minute and are indicated by the RGB LED blinking magenta very
sporadically. Once complete, your firmware should be uploaded. If
your device has any issues during or after the update, hit reset on the
Photon, and try again.
Once your code is uploaded, the RGB LED should go back to breathing
cyan to indicate it’s connected and running.
Now, open your favorite serial terminal program. Connect to the Photon at
9600 baud, and open a terminal.
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Once the terminal is connected, press any key to start streaming weather
data. You should now see weather data printing out!
From here, the sky is the limit! You can utilize the Photon’s Internet
connectivity to post your data to all kinds of data collection services. You
can also connect any combination of optional peripherals to the Weather
Shield to create a custom weather station suited to your needs.
Resources and Going Further
Here are a few links that should help with any further questions you may
have about the Photon Weather Shield:
SparkFun Photon Weather Shield GitHub Repo – this is where to go
for all the example code and hardware files.
Photon Weather Shield Schematic – Lots of juicy details found here.
Particle Documentation Pages – go here to set up and configure your
Photon (or other Particle devices)
Particle Community Forum – anything that you couldn’t find in the
docs should be easily found in the community forum. If you are
having trouble, search this forum first, as many of the answers are
there already.
If you would like to use the Photon and the Weather shield with
Microsoft’s cloud service, Azure, check out this great tutorial by Paul
There is a great tutorial on from Dan Fein that goes over
how to completely enclose your weather shield and send your data to
Using some additional stackable headers, the Weather Shield pairs very
well with any of our other Photon Shields. Check out our hookup guides for
those shields:
Photon Battery Shield
Hookup Guide
The Photon Battery Shield has
everything your Photon needs to run
off, charge, and monitor a LiPo
Photon Wearable Shield
Hookup Guide
Learn how to use the Photon
Wearable Shield for your next
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If you want to collect weather locally rather than sending it to the web,
check out the Arduino Weather Shield Hookup Guide.
battery. Read through this hookup
guide to get started using it.
Photon OLED Shield Hookup
The Photon OLED Shield has
everything you need to add a small
yet crisp OLED screen to your
Photon projects. This hookup guide
ill show you how to get started.
Photon IMU Shield Hookup
Learn how to use the SparkFun
Photon IMU Shield for your Photon
device which houses an on-board
LSM9DS1 system-in-a-chip that
houses a 3-axis accelerometer,
3-axis gyroscope, and 3-axis
rduino Weather Shield Hookup Guide V1
ARCH 2, 201
Read humidity, pressure and luminosity quickly and easily. Add wind
speed, direction and rain gauge for full weather station capabilities.
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