Setting up InfluxDB and Grafana for storing and viewing Arduino measured sensor values

Sending data to InfluxDB using Arduino over HTTP

We are going to use an Arduino (any model) with an Ethernet shield. You can also perform the same task with WiFi shield with some minor changes in the code.

Arduino Mega with Ethernet shield

Arduino Mega with Ethernet shield

The code

Since I only have 1 Arduino at hand and no actual sensors, I am going to emulate the test scenario in the code. But You can of course change to code according to your needs. The important part of the code is how to write into the buffer and how to calculate exact length of the content so we can make the HTTP parser of InfluxDB happy! This can be done through the magic of sprintf function which can write into a buffer char array and return number of written bytes.

Here is the code, I have comment it throughly so it should be obvious what it does. If you have any questions, feel free to ask in the comment section or in the embedonix’s forum.

Notes regarding the code

Although I have commented the code thoroughly, here is a brief description of the code:

  • Lines 4 to 16 are variables required for setting up and connecting to the server using the Ethernet shield. In my case, the Arduino was connected to my own laptop in a loop-back configuration, so the server address for InfluxDB would be obviously 192.168.0.1. If you are planning to connect your Arduino to a router or you are using WiFi, you must make sure to put the correct address in the eth_server[] variable!
  • In line 20 we have defined an integer equal to 2048, which is the size of our buffer to write the insertion query in it.
  • Line 23 is the definition and initialization of the buffer.
  • the get_place function is just used to get an imaginary place out of 4 places
  • the eth_send_data function is used to generate and send the correct HTTP POST request to the InfluxDB server
  • the loop function is used to continuously send some values in the range of 30 to 50 as temperature and a multiple of it as humidity and light values

So all and all, what you need to pay attention is the correct usage of writing a message into a character array buffer using sprintf function and using its return values to know where to continue inserting into the buffer.

In the next step, we will see how does the data is being transmitted and how to see the raw data in the InfluxDB’s administration panel.

Saeid Yazdani

An Electronics Engineer with passion in Embedded Systems, Wireless Sensor Networks, Assembly, Desktop and Mobile Development, Web Development and generally anything that has to do with hardware and software of any kind!

17 Comments:

  1. Thanks for sharing !!!

    Code “as-is” is giving me very weird errors en compiling for arduino 2560
    Still investigating on this

    C:\Program Files (x86)\Arduino\hardware\arduino\avr\cores\arduino\main.cpp: In function 'main':
    C:\Program Files (x86)\Arduino\hardware\arduino\avr\cores\arduino\main.cpp:51:1: error: unable to find a register to spill in class 'NO_REGS'
    }
    ^
    C:\Program Files (x86)\Arduino\hardware\arduino\avr\cores\arduino\main.cpp:51:1: error: this is the insn:
    (insn 294 291 297 19 (set (mem:QI (post_dec:HI (reg/f:HI 32 __SP_L__)) [0 S1 A8])
    (subreg:QI (reg/f:HI 271) 1)) \\WIN7PRO\__Projets\Grid Tie solar et vent\arduino\to influxdb\v033 test influx\v033\v033.ino:144 1 {pushqi1}
    (expr_list:REG_ARGS_SIZE (const_int 5 [0x5])
    (nil)))
    C:\Program Files (x86)\Arduino\hardware\arduino\avr\cores\arduino\main.cpp:51: confused by earlier errors, bailing out
    lto-wrapper: C:\Program Files (x86)\Arduino\hardware\tools\avr/bin/avr-gcc returned 1 exit status
    c:/program files (x86)/arduino/hardware/tools/avr/bin/../lib/gcc/avr/4.9.2/../../../../avr/bin/ld.exe: lto-wrapper failed

    collect2.exe: error: ld returned 1 exit status

    exit status 1
    Error compiling for board Arduino/Genuino Mega or Mega 2560.

    but werirdly compile fine for arduino due !
    ( from all I know, back end compiler is not the same at all )

    Using arduino 1.8.1 on windows 10

    • I have only tested this with Due. I’m not sure what the problem could be as I don’t have any other arduinos to test again. I just guess it has something tido with your Ethernet library.

  2. Thank, I tought you were using a 2560 .
    BTW You dont need the board to test compilation

    I got the stock etherne lib
    Playing around commenting uncomenting lines, still got weird compil errors

    I’ll use a Due if its the only issue , just a bit more expensive

  3. Found a work around

    Seems a documented bug in the latest GCC Compiler
    https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60040

    Aplied a similar work around I got from here
    https://github.com/arduino/Arduino/issues/3972

    I’ve Added
    void eth_send_data(char* data, int dataSize) __attribute__((__optimize__(“O2”)));

    On line 2 of your code
    Now compile Fine for 2560 , dont ask me more details !!!!!

    Thanks !

  4. Eratum
    You need 2 “spaces” before “__attribute__”
    Dont ask me why , but it is not the same

    void eth_send_data(char* data, int dataSize) __attribute__((__optimize__(“O2”)));

  5. Sorry … itsjust because I ve taken back My own comment and it wasent compiling again

    The issue is not the double space at all

    it is because this web page convert the ” character to another type of ”
    Just have to type it back to the “real” ” one …. hard to explain

  6. Just gave up, moved it all to arduino due, still having compilation error for 2560, but all working fine on due. Rest of instructions are all good.

    Except minor error, on page 5:
    $sudo dpkg -i https://grafanarel.s3.amazonaws.com/builds/grafana_4.0.2-1481203731_amd64.deb
    that should read
    $sudo dpkg -i grafana_4.0.2-1481203731_amd64.deb

  7. Orange Juice

    Hi. Code is working fine, I also needed to Optimize due to using a Mega. I am actually using a ENC28J60 with the UIPEthernet which is drop in for Ethernet.h however I dont get any respone from the server shown in Serial Monitor just the “Reply from InfluxDB”, The information is reaching influx it just doesnt display the 204 error it should in serial monitor.

    Dont suppose you have any pointers, not that its essential as the code is working.

    • I think you should play around with the delay value between sending and waiting for the response. Give it a try.

    • And perhaps you can show the changes you made to make it work on Mega? maybe that’s the problem. Jean-Francois Payeur comments show that it doesn’t work on Mega, although I have never tried it with Mega so can’t say for sure.

  8. Orange Juice

    Thanks for responding, great tutorial by the way.

    I followed Jean’s instructions as I got the same compile error an it was the GCC .

    Only difference in code compared with yours is i added this at the top of the skect.
    #include

    void eth_send_data(char* data, int dataSize) __attribute__((__optimize__(“O2”)));

    I will check delay and have a look into if it is a issue with UIPEthernet and syntax

  9. Orange Juice

    I managed to get it working by replacing availible with connected.

    Serial.println(“Reply from InfluxDB”);
    while(client.connected()) { //receive char
    Serial.print((char)client.read());
    }

    Thanks for a great tutorial.

  10. Pingback: InfluxDB Week in Review – Feb 13, 2017 | InfluxData

  11. Orange Juice

    It could be because I’m using the UIPEthernet library.

    I regret to inform the test I had running which was taking humidity readings from 3x DHT11 stopped sending information to influx after 60hours.
    Unsure on why it failed as it wasnt plugged into the computer so didnt have Serial Monitor open 🙁 I have reset the Arduino and hope for a better result, maybe it was my cat.

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