oled-bitchart

A practical extension based on micro:bit for data analysis

Tip

This MakeCode extension used YF-OLED as its dependency, so you should get an OLED screen with an I2C address 0x3D

For those OLED screens with I2C addresses of 0x3C, please fork this project and edit dependencies in pxt.json:

"dependencies": {
    "core": "*",
    "SSD1306_OLED": "github:tinkertanker/pxt-oled-ssd1306#v2.0.17"
},

And edit main.ts:

YFOLED.clear() --> OLED.clear()
/* and so on */

1. What Can This Extension Do?

If you've used the serial functionality of the micro:bit, you may know that MakeCode plots a line graph for the serial-printed data

However, if the micro:bit is not connected to a computer and is instead powered by an external source, this feature becomes unavailable.

Therefore, this extension aims to develop a similar "data analysis" feature for use with an external OLED screen and encapsulates it into a function for easy calling.

2. Extension Features & Usage

This project used DeepSeek V3-0324 model for coding and can be used as an extension in MakeCode.

main.ts contains a function called drawCurve. To use it, first add the extension in MakeCode, then call this function in a loop.

Explanation of the drawCurve() parameters:

• data: The data to be plotted, which can be sensor readings.
• sampleRate: The number of plots per second.
• jitter: The fluctuation range for the maximum and minimum values of the line graph. Since the graph automatically adjusts its range based on the input data, this process involves a full-screen refresh (which is slightly time-consuming). To minimize refresh frequency, the maximum/minimum value is increased in by one unit of jitter value. Additionally, this expands the range, avoiding unnecessary screen refreshes caused by sensor noise (see Runtime Explanation for details).
• topMargin_i: The distance from the top of the screen to the drawing area (unit: pixels). This parameter, along with the next one, is used to adjust the drawing area.
• bottomMargin_i: The distance from the bottom of the screen to the drawing area (unit: pixels).

Here's an example using MPU6050 as a temperature sensor (runtime photo) (MPU6050 extention: pxt-mpu6050):

YFOLED.init(128, 64)
MPU6050.initMPU6050(MPU6050.MPU6050_I2C_ADDRESS.ADDR_0x68)
basic.forever(function () {
    input.onButtonPressed(Button.A, function () {
        while (!input.buttonIsPressed(Button.B)) {
            BitChart.drawCurve(Math.round(MPU6050.readTempature(MPU6050.MPU6050_I2C_ADDRESS.ADDR_0x68)*100)/100, 5, 0.3, 9, 9)
        }
        YFOLED.clear()
        BitChart.resetGraph()
        MPU6050.resetMPU6050(MPU6050.MPU6050_I2C_ADDRESS.ADDR_0x68)
    })
})

Runtime Explanation

When the program starts, the maximum and minimum values (referred to as "extremes") of the graph are determined based on the current data input, with the range defined as Δ range = 2 × jitter. The current maximum and minimum values are displayed in the top-left and bottom-left corners of the screen(this feature may require manual adjustments (Why?Please view here) depending on the extension and OLED screen used, as it hasn't been tested on other extensions or OLED screens.).

If the current data value exceeds the extremes range, the maximum or minimum will be increased by one unit of jitter, the screen will be refreshed, and the graph will be redrawn with the updated range.

If the line graph exceeds the screen width (128 pixels), the historical data will be cleared, and plotting will restart from the left side of the screen.

The code has been optimized to ensure clear separation between the line graph and text display(by adjusting topMargin&bottomMargin). Enjoy data analyzing!

Recommended Use:

• Suitable for plotting not that big variations in data(temperature, humidity, brightness change, gas concentration, acceleration, sound level, etc.)
• Not recommended for detecting large changes, such as axis angle variations, as significant value fluctuations can make the graph difficult to interpret and cause frequent refreshes.

Runtime Image

This project should be helpful for data analysis. By adjusting the sampleRate, you can achieve long-term plotting, but be mindful of OLED burn-in. It is recommended to use it in conjunction with the Data Logger extension for both short- and long-term monitoring.

Open this page at https://meowcata.github.io/oled-bitchart/

Use as Extension

This repository can be added as an extension in MakeCode.

• open https://makecode.microbit.org/
• click on New Project
• click on Extensions under the gearwheel menu
• search for https://github.com/meowcata/oled-bitchart and import