Telegram_Bot_Consumable_Monitoring

CONCEPT : Use a telegram bot to receive a message as ESP8266 starts up,
repeat at a set time and sleep in between messages to save battery.
NOTE : this works one way, only sending messages, any response is ignored.
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Telegram Bot library written by Brian Lough and ammended by Bolukan
YouTube:  https://www.youtube.com/brianlough
Tindie:   https://www.tindie.com/stores/brianlough/
Twitter:  https://twitter.com/witnessmenow
github:   https://github.com/witnessmenow/Universal-Arduino-Telegram-Bot
github:   https://github.com/bolukan

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USE CASE : Generate an alert via Telegram when a consumable has run out
by closing a hardware switch that powers up an ESP8266. The battery
voltage level can be measured and also sent, together with the
statically set minimum battery level.

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USER VARIABLES : You need to use your WiFi SSID and password as well as
the bot token and chat id (see below).

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TELEGRAM BOT : You need to make a bot first to be able to use this. 
Search 'botfather' and you will find plenty information on how to
create your own telegram bot.
- Botfather will give out your unique bot token when he creates the
bot for you.
- Use @myidbot (IDBot) in Telegram or the HTTPS request method to
find out the chat ID of your bot.
- Also note that you need to "start" your bot before it will do
anything:
In Telegram type @botfather to open a chat. Type /mybots to show
and pick your bot(s).
From your bot, type /start to activate your bot. Type /stop
to de-activate it.

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HARDWARE REQUIREMENTS :
- For the ESP8266 to wake from deepsleep, it needs a connection
between RST and A0 (or whatever is your ADC pin)
- To be able to measure VCC you need to connect a resistor from VCC to A0.
The value of this resistor depends on wether there already is a voltage divider
in place like on the D1 mini and NodeMCU, or if it is a barebone ESP. For
example; D1 mini measuring ~5V it should be 180k ohm. Alternatively
you can use a multiturn potentiometer to exactly dial in the R value.

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IMPORTANT : with the 'DeepSleep' pin open it is very hard to (re)flash
as the ESP will go into deepsleep before you can upload the code.
So, to re-flash connect this pin to GND. However, it cannot be
connected to GND during boot as this will prevent the ESP from
booting up. So, reset and then connect.

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