In this project, we will be building upon our Telegram tutorial by showing you how to utilize Telegram to control your Raspberry Pi.
We will be doing this by utilizing the LUA interpreter that is built into the Telegram CLI which opens it up to quite a wide variety of functionality.
The LUA interpreter allows us to program certain functions that trigger when something occurs on the Telegram CLI, such as when it receives a message.
This interpreter allows us to do certain actions based on the received message, the two simple tasks we will be showing you how to do is a simple receive message and reply, and also how to set up the Telegram CLI so we can trigger an outside bash script and upload a photo automatically.
Before proceeding with the tutorial, ensure that you have completed our Telegram CLI tutorial as that sets up the basis for this guide.
Below are all the bits and pieces that I used for this guide on controlling your Raspberry Pi with Telegram CLI.
This tutorial was last tested on a Raspberry Pi 3 running Raspbian Stretch.
Writing your first script for Telegram CLI
1. Before you tackle this tutorial, you will first have had to complete our base Telegram tutorial as this takes you through all the steps of setting up Telegram on the Raspberry Pi.
Once you have finished setting up Telegram, you can continue with this tutorial. With this tutorial will be showing you how to utilize the Telegram CL’s LUA interpreter so we can actively monitor the received messages and take actions based on what we have received. Basically setting up our own Raspberry Pi telegram bot that will respond to commands that are sent to it.
For those who don’t know LUA is a very powerful, fast, lightweight and embeddable scripting language. Many applications use LUA to allow people to modify and extend their application easily.
In the Lua Script, we will be writing there will be seven different functions we must implement, even though we will only be using one of these we need to have all the functions in place to stop constant warnings.
This LUA script will be basic, with it replying to every message that says “ping” with “pong”, while simple it will give you an idea on how to handle text messages.
Let’s begin writing our LUA script for Telegram by running the following two commands on our Raspberry Pi.
cd ~/tg nano actions.lua
2. With our actions.lua file opened we will need to write the following lines of code into it. We will explain each section as we write them into the file. Remember to retain the tabs as LUA is whitespace sensitive.
function on_msg_receive (msg) if msg.out then return end if (msg.text=='ping') then send_msg (msg.from.print_name, 'pong', ok_cb, false) end end
This code is the main function that we will be using in this tutorial, and this function is called every time that the Telegram CLI receives a new message. We first make sure that this isn’t a message that we just sent by checking if msg.out is true.
If it is false, we then proceed to check the content of the message. If the message is equal to the string ping, we then proceed to send a message back in reply.
function on_our_id (id) end
When this function is called, it provides the id of the currently logged in user. We do not need to implement anything for this as we are focusing on receiving and replying to messages.
function on_secret_chat_update (user, what_changed) end function on_user_update (user, what_changed) end function on_chat_update (user, what_changed) end
These three functions are called when there is updated information on a user, and the variables provided back is the user that was updated and an array of what changed.
function on_get_difference_end () end
This function is called after the first get_difference call. It means that all updates after the last client execute have been received.
function on_binlog_replay_end () end
This function is called after the replay of old events has ended.
3. Once you have finished typing in the code, you should end up with something like what is displayed below. Check over your code and ensure you haven’t made any mistakes.
function on_msg_receive (msg) if msg.out then return end if (msg.text=='ping') then send_msg (msg.from.print_name, 'pong', ok_cb, false) end end function on_our_id (our_id) end function on_secret_chat_update (user, what_changed) end function on_user_update (user, what_changed) end function on_chat_update (user, what_changed) end function on_get_difference_end () end function on_binlog_replay_end () end
Once you are happy with the code that you have written press CTRL + X then Y then ENTER to save the file.
4. With our LUA script now written we can finally test to see if it is working successfully with Telegram. To do this, we need to run the following two commands on our Raspberry Pi. These commands will launch Telegram CLI and set up the script to utilize.
cd ~/tg bin/telegram-cli -k tg-server.pub -W -s actions.lua
5. Now that the Telegram CLI (Command line interface) is now up and running with our script, we need to send a message to our Telegram account.
The message you need to send is ping. Immediately upon sending the message the Raspberry Pi should receive it, check whether the message matches to ping then reply with the message Pong.
If you receive Pong on your device, you have successfully written your first LUA script that lets your Raspberry Pi Telegram bot reply automatically to messages.
Over the next section, we will be diving into this concept even further, this time showing how you can use the LUA script to run an external batch script that will take a photo and send it over Telegram to the receiver.
This sample script will give you an idea on how you could use Telegram to do all sorts of things on your Raspberry Pi, and not be bound by LUA’s limitations. Meaning you could use it to control devices over your GPIO pins if you wanted.
Automatically Sending Photos through Telegram
1. To proceed with this section of the tutorial, you will need to of installed and set up the Raspberry Pi camera as we will be using that to automatically take photos and send them when our LUA script receives a message.
To get started we will make a directory where we will temporarily store the images we take and the bash script we will need to write for our LUA script to call.
Run the following command on our Raspberry Pi to create our new folder.
sudo mkdir ~/camera
2. With the folder created let’s write our bash script, this script will basically make a call to the raspistill application so the Raspberry Pi will take a photo and save it into our new /home/pi/camera/ directory.
3. Within this file write the following lines of code.
#!/bin/bash raspistill -w 800 -h 600 -o /home/pi/camera/photo.jpg
Once you have written in these two lines, save the file by pressing CTRL + X then Y and then finally hit ENTER.
4. Now before we go ahead and modify our actions.lua script, we will need to make sure we can execute our new bash script from our Lua script.
sudo chmod 755 ~/camera/camera.sh
5. Finally, we can move onto modifying our actions.lua script that we wrote earlier in the tutorial.
Run the following command to begin editing the file on your Raspberry Pi.
6. In this file, we need to add the following code.
if msg.out then return end if (msg.text=='ping') then send_msg (msg.from.print_name, 'pong', ok_cb, false) end
if (msg.text=='photo') then os.execute('/home/pi/camera/camera.sh') send_photo (msg.from.print_name, '/home/pi/camera/photo.jpg', ok_cb, false) end
This new bit of code works by checking for any message that is photo upon interpreting the correct message we then execute the camera.sh bash script that we wrote earlier in this tutorial.
After the script has been executed we can then utilize the Telegram CLI’s send_photo function to send the photo we captured with our bash script.
Simply put this takes a photo from your Raspberry Pi camera then sends it back to the user that sent the message photo to your Telegram account.
7. Once you have written these new lines into our actions.lua script, you should end up with a file that looks like what we have shown below.
function on_msg_receive (msg) if msg.out then return end if (msg.text=='ping') then send_msg (msg.from.print_name, 'pong', ok_cb, false) end if (msg.text=='photo') then os.execute('/home/pi/camera/camera.sh') send_photo (msg.from.print_name, '/home/pi/camera/photo.jpg', ok_cb, false) end end function on_our_id (our_id) end function on_secret_chat_update (user, what_changed) end function on_user_update (user, what_changed) end function on_chat_update (user, what_changed) end function on_get_difference_end () end function on_binlog_replay_end () end
Once you are sure you have entered the new lines correctly you can save and quit out of the file by pressing CTRL + X then hit Y and then ENTER.
8. Now finally we can test our new code, simply run the same telegram-cli command that we ran earlier in the tutorial by running the following two commands on your Raspberry Pi.
cd ~/tg bin/telegram-cli -k tg-server.pub -W -s actions.lua
9. With the Telegram CLI now running with your actions.lua script, you can now send yourself a message that says “photo“. Your Raspberry Pi should pause temporarily as it takes the photo then you should be able to see the upload progress as it sends the photo.
Hopefully, by now you have successfully set up your Raspberry Pi with Telegram and now have a good understanding on how to use the LUA script to allow Telegram to control your Raspberry Pi. You can obviously extend this further by setting it up to control even other devices through the GPIO pins.
You can find more documentation on the functions that you can utilize within the LUA script that Telegram CLI provides by going to the developers LUA documentation page.
We hope by the time you have gotten to this point you have learned how to control your Raspberry Pi by using Telegram, we should of by now given you the basic understanding of how it works and how you can utilize it to do numerous things with your Raspberry Pi.
Feel free to drop a comment below if you have enjoyed this Raspberry Pi Telegram Bot tutorial or need some help getting it up and running.