OpenBeken Charts Driver - configurable and flexible measurement history on your device

OpenBeken now features a scriptable charts driver that allows you to display an arbitrary number of variables with an arbitrary number of axes. This means you can, for example, show your temperature and humidity history, or a voltage or power, or practically any variable you want. This is done entirely without Home Assistant, everything is handled by OBK device. Here I will show you a basic configuration of such driver and some sample scripts utilizing that.

This tutorial assumes you have OBK displayed:
https://github.com/openshwprojects/OpenBK7231T_App
The following will run on many platforms, including:
- BK7231T (WB3S, WB2S, WB2L, etc)
- BK7231N (CB2S, CB2L, WB2L_M1, etc)
- BK7231M, this is a non-Tuya version of BK7231N with 00000000 keys, also sometimes in BL2028 flavour
- T34 is based on BK7231N, see flashing trick
- BL2028N is a Belon version of BK7231N
- XR809 (XR3, etc)
- BL602 (SM-028_V1.3 etc), see also BL602 flash OBK via OTA tutorial
- LF686 (flash it as BL602)
- W800 (W800-C400, WinnerMicro WiFi & Bluetooth), W801
- W600 (WinnerMicro chip), W601 (WIS600, ESP-01W, TW-02, TW-03, etc)
- LN882H by Lightning Semi - datasheet, see flashing how-to, see sample device teardown and flashing, see new flash tool, see dev board
- Windows, via simulator
- ESP32 (WIP platform)

Let's start with checking if your build has "charts" driver:

If it's not present, set the ENABLE_DRIVER_CHARTS to 1 in obk_config.h for the platform of your choice by following paragraphs "Per-Pull Request Builds" and "Customizing your own build" in this guide to get your custom build made online (no toolchain required):
https://www.elektroda.com/rtvforum/topic4033833.html#20946719

Ok, now I assume that you have "charts" driver in your build.

So, the charts can be created in autoexec.bat. If you don't know where to create autoexec.bat, see this tutorial:

Now, once you have basics ready, it's time to check some sample chart scripts!

First, you need to know the basic steps and then we'll look at sample scripts. So, steps are the following:
1. start the chart driver
2. setup the samples count (they are stored in a loop), the number of variables and the number of axes
3. set the variable names and their respective axes
4. setup the axes
5. add data to chart
It may sound complicated at first but it's very easy, let's check the samples.

And before I forgot - in the early versions you may also need to add one more command to autoexec.bat - you need to disable page refresh with:

This may be fixed soon. The dynamic charts update is not yet ready.

Sample chart 1 - simplest temperature chart
This is an example of a basic chart displaying temperature data over time, however, for a demonstration purposes, the data is hardcoded. The chart holds 16 data samples and focuses on a single variable, "Temperature", plotted on one axis.

Result:


Sample chart 2 - multiple variables of single type
The same approach can be used to display multiple measurements of the same type. Here, for example, we display 3 different temperature values:

Result:



Sample chart 3 - two y axes
Charts driver can also offer you multiple y axes. This way you can display, for example, both temperature and humidity data:

Result:


Sample chart 4 - battery and pressure
Of course, you can display any kind of data you want. Here is for example a voltage and the pressure chart:

Result:



Sample chart 5 - third y axis
While not recommended, it's still possible to add a third unit axis. Here is a VCP (Voltage/Current/Power) graph:

Result:



Final sample - how to plot DHT11 measurements?
All samples so far had hardcoded time values, but it's also possible to get time from NTP. For this purpose, first we need to start NTP and wait for NTP connect:

Then we can periodically call chart_addNow command, with, for example, given channel content:

Alternatively, we can use repeating event for that - it's the same:

And then we can build upon that. Here is a full code for DHT11 demo:

And here is sample output (from @divadiow , thank you for testing):

As you can see, our charts driver can work well with DHT11.


Remember that you can hover mouse over datapoint
If you are not sure what is the value of given datapoint, you can always hover mouse about it to get more details:


Chart commands
Summing up, charts have the following commands:

Command	Arguments	Description
chart_create	samplesCount variablesCount axesCount	Creates a chart with a specified number of samples, variables, and axes.
chart_setVar	index varName axisName	Associates a variable with a specific axis.
chart_setAxis	axisIndex axisName flags label	Sets up an axis with a name, flags, and label. Currently flags can be 0 (left axis) or 1 (right axis)
chart_add	ntpTime var1 [var2 ...]	Adds data to the chart with specified variables at a specific NTP time.
chart_addNow	var1 [var2 ...]	Adds data to the chart using the current NTP time.

Of course, they are subject to change in the future, so you may want to check the latest docs here:
https://github.com/openshwprojects/OpenBK7231T_App/blob/main/docs/commands.md
https://github.com/openshwprojects/OpenBK7231T_App/blob/main/docs/autoexecExamples.md


Planned features
This is a very early version. Some improvements are coming soon:
- soon it will be possible to specificy RGB color per variable
- currently OBK is using chart.js library from web, but it is planned to allow users to specify alternative chart.js path so they can fetch it from their own server
- persistent data storage (optimized to reduce flash wear) is also planned
You can also give your own feature suggestions and we will do our best to implement them!

Summing up
I think that having charts handled directly on device can be very useful, especially for people who do not want to set up their own Home Assistant instance. With our charts driver, you can have just a single IoT device in your house and still enjoy charts data. No Home Assistant, no external server, nothing else is needed! I hope some of you will find this little feature useful. Stay tuned, more updates coming soon.