node-it8951

This is a port of the IT8951-ePaper C driver from Waveshare combined with some concepts from the Python PaperTTY IT8951 Driver

Key features of this library:

• Fast, uses native GPIO libraries
• Auto VCOM Detection
• Supports 1,2,4 Bits Per Pixel (BPP)
• Remappable Pins
• Configurable Buffer Size, if you intend to change your SPI buffer size

Important Information For 1BPP Drawing For 1BPP mode (black/white), some devices (E.g. Waveshare 6" HD E-Paper) have to turn on 4-byte align which forces the drawing of X and Width setting to be factors of 32.
Additionally, we still need to, depite the 1BPP definition, we would still have to provide 8-bit buffers (as a known workaround).
For the devices that support higher BPP, I would certainly recommend using those since you neither gain the fidelity nor the performance of using 1BPP.
See: https://www.waveshare.com/wiki/Template:EPaper_Codes_Descriptions-IT8951

In-Action Shot

Dependencies

1. GPIO

Getting Started

npm install node-it8951

Example Code

    const IT8951 = require('node-it8951');

    const display = new IT8951({ MAX_BUFFER_SIZE: 32797, ALIGN4BYTES: true });
    display.init();
    display.wait(2000);
    sample4BPP(display);
    display.wait(2000);
    display.clear();
    sample2BPP(display);
    display.wait(2000);
    display.clear();
    sample1BPP(display);
    display.wait(2000);
    display.clear();
    display.close();



    function sample4BPP(display) {
        display.config.BPP = 4; // BPP4
        const colors = [0xFF,0xEE,0xDD,0xCC,0xBB,0xAA,0x99,0x88,0x77,0x66,0x55,0x44,0x33,0x22,0x11,0x00];
        const segmentHeight = Math.trunc(display.height/colors.length);

        for (let i=0; i<colors.length; i++) {
            const buffer = Buffer.alloc(display.width * segmentHeight * display.config.BPP / 8, colors[i]);
            display.draw(buffer, 0, segmentHeight * i, display.width, segmentHeight);
        }
    }

    function sample2BPP(display) {
        display.config.BPP = 2;
        const hwidth = display.width/2;
        const hheight = display.height/2;
        const colors = [0xFF, 0xAA, 0x55, 0x00];
        for (let i=0; i<colors.length; i++) {
            const buffer = Buffer.alloc(hwidth * hheight * display.config.BPP / 8, colors[i]);
            display.draw(buffer, i%2 * hwidth, Math.trunc(i/2) * hheight, hwidth, hheight);
        }
    }

    function sample1BPP(display) {
        display.config.BPP = 1;
        const hwidth = display.width/2;
        const colors = [0xFF, 0x00];
        const buffer = Buffer.alloc(roundTo32(display.width/2) * display.height, 0x00);
        display.draw(buffer, 0, 0, roundTo32(display.width/2), display.height);
        display.config.BPP = 4;
    }


    function roundTo32(v) {
        return v = v - (v % 32);
    }

Functions Calls

IT8951(config) Constructor that takes in a suite of parameters

    const config = {
        MAX_BUFFER_SIZE: 4096, // Can be changed to 32786 for example
        PINS: {
            RST: 11, // 17 BCM
            CS: 24, // 8 BCM
            BUSY: 18, // 24 BCM
        },
        VCOM: 2150, // Supports autodetection so if this is wrong, it will fix that for you
        BPP: 4, // Rendering BPP (can be changed as required before each draw or display call). Valid values are 1, 2, 4
        ALIGN4BYTES: false, // Use to support BPP1 situations for some specific Waveshare devices
        SWAP_BUFFER_ENDIANESS: true, // Repacks the buffer to Llittle Endian format
    };

IT8951.init()
Runs the initialization sequence (Required).

IT8951.draw(buffer, x, y, w, h, display_mode)
Transfers the buffers to the device and refreshes the screen to the specific coordinates and dimensions.
Optional display_mode can be forwarded to displayArea call. Only call this if you are familiar with your device settings:

• DISPLAY_UPDATE_MODE_INIT = 0, A fast non-flashy update mode that can go from any gray scale color to black or white.
• DISPLAY_UPDATE_MODE_GC16 = 2, For more documentation on display update modes see the reference document= http=//www.waveshare.net/w/upload/c/c4/E-paper-mode-declaration.pdf
• DISPLAY_UPDATE_MODE_A2 = 6, A flashy update mode that can go from any gray scale color to any other gray scale color.

IT8951.displayArea(x, y, w, h, display_mode)
Internal method used to repaint the display's based on the specific coordinates and dimensions.

IT8951.clear(color=0xFF, display_mode)
Flushes the screen to white, optionally send 0x00 for black.

IT8951.wait()
GPIO delay before the next event.

IT8951.activate()
Sets up the device, enable all clocks and go to active state. Already run as part of init sequence.

IT8951.reset()
Resets the display, Already run as part of init sequence.

IT8951.standby()
Gates of all clocks and goes into a standby state.

IT8951.sleep()
Disable all clocks and go to sleep. Already run as part of close sequence.

IT8951.close()
Shutsdown the driver and releases control of the GPIO and SPI pins.

TODO

• Test driver on other IT8951 Devces
• Support Rotation

Other Resources

• C driver from Waveshare
• Python PaperTTY IT8951 Driver
• IT8951 Specifications Document