espIOT code for PIC16F887 MCU is written in C language. It is compiled using MPLAB IDE version 8.91 and HI-TECH C compiler version 188.8.131.5220. The generated hex code is burnt into the MCU chip using MPLAB ICD 2 programmer board.
Download PCB and component layout PDFs: click here
Download source code: click here
Construction and testing
An actual-size, single-side PCB layout of the Wi-Fi temperature logger is shown in Fig. 6. and its component layout in Fig. 7. When the circuit is switched on, the program initialises the LCD and flashes welcome message ‘ESP Temp Logger’ on the LCD.
If there is any display problem on the LCD, check voltages at various points as listed in the test point table. If the LCD is showing a proper message, go to www.thingspeak.com
First, sign in to www.thingspeak.com and then create your own channel by creating a field as shown in Fig. 8.
After saving the channel, you will receive channel ID and two API keys—a write API key (it is to be used in our C code) and a read API key (it is used to check the data from website on your smartphone or PC). Make a note of these keys as you will need these later.
Before using the system, ensure that Esp8266 module baud rate is changed to 9600 as most of these have 115200. Also, a Wi-Fi modem with an Internet connection should be kept near your circuit board.
Next, make the following changes in the espIOT.C code:
1. Replace eRocks14 with your own Wi-Fi name
2. Replace erocks2014 with your own Wi-Fi password
3. Replace API key with your own API key received
ESP8266 works on basic AT commands similar to the ones used in any GSM module interfacing project. It can be easily checked and tested from HyperTerminal of Windows. The link to AT commands is www.pridopia.co.uk/pi-doc/ESP8266ATCommandsSet.pdf
In the latest version of ESP8266 firmware, baud rate setting command AT+CIOBAUD is no longer supported. You can replace this command by AT+IPR. The detail of this command can be found on www.esp8266.com/viewtopic.php?f=13&t=718
When you open your channel under Data IMPORT/EXPORT section, you will get your API key. Call this link www.api.thingspeak.com/update?key=[THINGSPEAK_KEY]&field1=0 by changing the field value and give any number you want to upload. In Private View section, you will see a graph of the data as shown in Fig. 9.
For checking the results on a smartphone or PC, a link is provided in the respective channel. It would be something like http://api.thingspeak.com/channels/channel_id/feed.json?key=api_key
In this link, API key is replaced by Read API key and channel id is replaced by the user’s channel ID. Copy and paste this link in search bar of the browser in your smartphone or PC. You will get the recorded temperature data information.
If temperature data has been uploaded, you will be able to see the graph here. Temperature data on www.thingspeak.com is shown in Fig. 9. You are now ready to go with your first IoT project.
This project can be used as a guide for various other related projects for your home systems; not just temperature but also energy consumption and many other interfaces that can be easily checked on your smartphone.
Osho Gera is a second-year B.Tech student, studying at Bharati Vidyapeeth’s College of Engineering, New Delhi