it8951/lib/spi.ts

Raspberry Pi node.js module for e-papers controlled by IT8951

/**
 * Internal class for SPI connection
 * @internal
 * @packageDocumentation
 */
// eslint-disable-next-line @typescript-eslint/no-var-requires
const it8951 = require('../build/Release/spi'); // eslint-disable-line node/no-unpublished-require

/**
 * Pin asignments for the non SPI pins in use. As long as bcm2835 is used these are hardware pins.
 *
 * @enum {number}
 */
enum PINS {
    /**
     * Chip select.
     */
    CS = 8,
    /**
     * Ready pin. Pulls high when it8951 is ready to recieve communication.
     */
    READY = 24, // HRDY
    /**
     * Reset pin, pull low to reset controller.
     */
    RESET = 17,
}

/**
 * Possible pin values when using {@link setPin} or {@link readPin}
 *
 * @enum {number}
 */
export enum PIN_VALUE {
    /**
     * Pin low, i.e. no voltage.
     */
    LOW = 0,
    /**
     * Pin high, i.e. 3.3v on specified pin.
     */
    HIGH = 1,
}

/**
 * The SPI class is a convenience class for sending data over SPI. In practice, it only exposes the methods needed for the main {@link IT8951} class.
 *
 * @export
 * @class SPI
 */
export class SPI {
    /**
     * Creates an instance of SPI.
     *
     * This will initialise the c++ code, then set chip select pin high and trigger a controller reset.
     */
    constructor() {
        it8951.init();
        this.setPin(PINS.CS, PIN_VALUE.HIGH);
        this.reset();
    }

    /**
     * Reset the controller.
     */
    public reset() {
        return it8951.reset();
    }

    /**
     * Write the words in `data` over the SPI interface.
     *
     * @param data Array of words to write.
     */
    public writeWords(data: Uint16Array) {
        this.setPin(PINS.CS, PIN_VALUE.LOW);
        this.waitForReady();
        it8951.writeWords(data);
        this.setPin(PINS.CS, PIN_VALUE.HIGH);
    }

    /**
     * Reads `length` number of words from the SPI interface.
     *
     * @param length Number of words to read.
     */
    public readWords(length: number): Uint16Array {
        const data = new Uint16Array(length);
        this.setPin(PINS.CS, PIN_VALUE.LOW);
        this.waitForReady();
        const response = it8951.readWords(data, length);
        this.setPin(PINS.CS, PIN_VALUE.HIGH);
        return response;
    }

    /**
     * Writes a sequence of bytes over the SPI interface.
     *
     * @param data Array of bytes to write.
     */
    public writeBytes(data: Uint8Array) {
        this.setPin(PINS.CS, PIN_VALUE.LOW);
        this.waitForReady();
        it8951.writeBytes(data);
        this.setPin(PINS.CS, PIN_VALUE.HIGH);
    }

    /**
     * Read pin `pin`.
     *
     * @param pin Hardware pin number to read
     */
    public readPin(pin: number): PIN_VALUE {
        return it8951.readPin(pin);
    }

    /**
     * Set pin `pin` to `value`.
     *
     * @param pin Hardware pin number to set
     * @param value Value to set
     */
    public setPin(pin: number, value: PIN_VALUE) {
        it8951.setPin(pin, value);
    }

    /**
     * Synchronously blocks until the SPI is ready for new messages.
     */
    public waitForReady() {
        it8951.waitForReady();
    }
}