Raspberry Pi - Thingspeak

Thingspeak

About ,Account and Channel Creation

ThingSpeak is a webservice, open source Internet of Things (IoT) application and API to store and retrieve data from things.

The service is free and offers a very basic http based service for starters.The platform is very limited but suits the context, for now, since its extremely easy to setup.
Lets start

Sign Up for an account in thingspeak
Create a new channel.

You can select enable/select more fields in a channel to view/capture multiple data streams.Also you may enable public view to publish the channel to anyone with access to your channel id

Go to the channel setting and copy the API Write key.

The API key should be kept secure since it forms the one and only layer of authentication.

Configuration

Raspberry Pi will work as a gateway to publish data from sensors interfaced via its GPIO or sensors connected via external devices such as Arduino.To proceed make sure that you have a working internet connection on Raspberry Pi that can connect to Thingspeak servers.
We will use an RPi and Arduino to better understand the concepts.

Setup Arduino to send serial data over USB.You may use LDR experiment as an example.
Connect Arduino to RPi via USB.Try
```
dmesg | grep tty
```
to check and identify the device.
Change permissions to ensure read access to the device
```
sudo chmod 777 /dev/ttyACM0
```
The device address should be as obtained from previous line of code.It can be ACM0 ACM1 (ACMx series ) or USB0 USB1 (USBx series)

Code

The code for RPi can be cloned from my github repo. Try in terminal

git clone https://github.com/akshaim/thingspeak

The code can also be downloaded from here

Go to the cloned/downloaded repository and edit thingspeaktest.py. Try
```
nano thingspeaktest.py
```
Enter you write api key in the field provided and save the file.
Press Ctrl + O and then enter to save.Press Ctrl + X to exit from nano
Execute the code.Try
```
python thingspeaktest.py
```
If you get status code as 200 ,you should see an entry (value 12)in your thingspeak channel webview (private/public depending on your channel settings)

Change the field value to observe change in webview (fieldchart).

Now edit thingspeaktestloop.py and add the write API key as in the previous case.
Run the code. Try
```
python thingspeaktestloop.py
```

The code sends a static value(default 12) to thingspeak server in a 16 second interval and updates the status to user

Now edit thingspeaktestserial.py as in the previous case.The python code sends a dynamic value from Arduino to thingspeak server

Ensure that the device address(arduino) is same as one you observed. Default value is /dev/ttyACMO