main.ts

/**
 * SCD30 block
 */
//%color=#444444 icon="\uf185" block="SCD30"
namespace SCD30 {

    // Protokollbeschreibung des Sensors
    // https://www.sensirion.com/fileadmin/user_upload/customers/sensirion/Dokumente/9.5_CO2/Sensirion_CO2_Sensors_SCD30_Interface_Description.pdf

    //let data = pins.createBuffer(2)
    //data[0] = 0xBE
    //data[1] = 0xEF
    //hier muss die Dezimalzahl 146 rauskommen!
    //    CRC(0xBEEF) = 0x92
    //data[0] ist immer das höchste Byte!
    //console.log("::"+crc(data)+"-"+0x92)
    function crc(data: Buffer, offset: number = 0 ): number {
        let current_byte;
        let crc = pins.createBuffer(1)
        crc.setNumber(NumberFormat.UInt8LE, 0, 0xFF)
        let crc_bit;

        //calculates 8-Bit checksum with given polynomial 
        for (current_byte = offset; current_byte < offset+2; ++current_byte) {
            crc.setNumber(NumberFormat.UInt8LE, 0, crc.getNumber(NumberFormat.UInt8LE, 0) ^ data.getNumber(NumberFormat.UInt8LE, current_byte))
            for (crc_bit = 8; crc_bit > 0; --crc_bit) {
                if (crc.getNumber(NumberFormat.UInt8LE, 0) & 0x80)
                    crc.setNumber(NumberFormat.UInt8LE, 0, (crc.getNumber(NumberFormat.UInt8LE, 0) << 1) ^ 0x31)
                else
                    crc.setNumber(NumberFormat.UInt8LE, 0, (crc.getNumber(NumberFormat.UInt8LE, 0) << 1))
            }
        }
        return crc.getNumber(NumberFormat.UInt8LE, 0);
    }

    let temperature: number = 0
    let humidity: number = 0
    let co2: number = 0
    
    control.inBackground(() => {
        enableContinuousMeasurement()
        while (true) {
            readMeasurement()
            basic.pause(2000)
        }
    })
    
    function enableContinuousMeasurement(): void{
        let commandBuffer = pins.createBuffer(5)

        //command
        commandBuffer[0] = 0x00 
        commandBuffer[1] = 0x10 
        //pressure in mBar
        //200m = 987mBar = 0x03DB
        commandBuffer[2] = 0x03 //MSB 
        commandBuffer[3] = 0xDB //LSB
        commandBuffer[4] = crc(commandBuffer,2) 

        pins.i2cWriteBuffer(0x61, commandBuffer, false)
    }
    /**
     * Calibrates sensor to 400ppm
     */
    //% weight=87 blockGap=8
    //% block="setCalibration400ppm" 
    //% blockId=setCalibration400ppm
    export function setCalibration400ppm(): void {
        let commandBuffer = pins.createBuffer(5)

        //command
        commandBuffer[0] = 0x52 
        commandBuffer[1] = 0x04 
        //pressure in mBar
        //200m = 987mBar = 0x03DB
        commandBuffer[2] = 0x01 //MSB 
        commandBuffer[3] = 0x90 //LSB
        commandBuffer[4] = crc(commandBuffer,2) 

        pins.i2cWriteBuffer(0x61, commandBuffer, false)
    }

    /**
     * read calibration data
     */
    //% weight=87 blockGap=8
    //% block="getCalibration" 
    //% blockId=getCalibration
    export function getCalibration(): number {
        let buf = pins.createBuffer(3)
        pins.i2cWriteNumber(0x61, 0x5204, NumberFormat.UInt16BE,false)
        basic.pause(10)
        buf = pins.i2cReadBuffer(0x61, 3, false)
        let res = (buf[0]<<8) + buf[1]
        return res
    }
    /**
     * read sensor version
     */
    //% weight=87 blockGap=8
    //% block="getVersion" 
    //% blockId=getVersion
    export function getVersion(): string {
        let buf = pins.createBuffer(3)
        pins.i2cWriteNumber(0x61, 0xD100, NumberFormat.UInt16BE,false)
        basic.pause(10)
        buf = pins.i2cReadBuffer(0x61, 3, false)
        let res = "" + buf[0] + "." + buf[1]
        return res
    }

    function readReady(): boolean{
        let buf = pins.createBuffer(3)
        pins.i2cWriteNumber(0x61, 0x0202, NumberFormat.UInt16BE,false)
        basic.pause(10)
        buf = pins.i2cReadBuffer(0x61, 3, false)
        let res = (buf[0]<<8) + buf[1]

        if(buf[1] == 1){
            return true
        }else{
            return false
        }
    }

    function readMeasurement(): void{
        while(readReady() == false){
            basic.pause(10)
            //serial.writeLine("waiting in: readMeasurement()")
        }
        let buf = pins.createBuffer(18)
        let tbuf = pins.createBuffer(4)
        pins.i2cWriteNumber(0x61, 0x0300, NumberFormat.UInt16BE, false)
        basic.pause(10)
        buf = pins.i2cReadBuffer(0x61, 18, false)
        
        //co2
        tbuf.setNumber(NumberFormat.Int8LE, 0, buf.getNumber(NumberFormat.UInt8LE, 0))
        tbuf.setNumber(NumberFormat.Int8LE, 1, buf.getNumber(NumberFormat.UInt8LE, 1))
        tbuf.setNumber(NumberFormat.Int8LE, 3, buf.getNumber(NumberFormat.UInt8LE, 3))
        tbuf.setNumber(NumberFormat.Int8LE, 4, buf.getNumber(NumberFormat.UInt8LE, 4))
        co2 = tbuf.getNumber(NumberFormat.Float32BE, 0)
        co2 = Math.round(co2*100)/100

        //temperature
        tbuf.setNumber(NumberFormat.Int8LE, 0, buf.getNumber(NumberFormat.UInt8LE, 6))
        tbuf.setNumber(NumberFormat.Int8LE, 1, buf.getNumber(NumberFormat.UInt8LE, 7))
        tbuf.setNumber(NumberFormat.Int8LE, 3, buf.getNumber(NumberFormat.UInt8LE, 9))
        tbuf.setNumber(NumberFormat.Int8LE, 4, buf.getNumber(NumberFormat.UInt8LE, 10))
        temperature = tbuf.getNumber(NumberFormat.Float32BE, 0)
        temperature = Math.round(temperature*100)/100

        //humidity
        tbuf.setNumber(NumberFormat.Int8LE, 0, buf.getNumber(NumberFormat.UInt8LE, 12))
        tbuf.setNumber(NumberFormat.Int8LE, 1, buf.getNumber(NumberFormat.UInt8LE, 13))
        tbuf.setNumber(NumberFormat.Int8LE, 3, buf.getNumber(NumberFormat.UInt8LE, 15))
        tbuf.setNumber(NumberFormat.Int8LE, 4, buf.getNumber(NumberFormat.UInt8LE, 16))
        humidity = tbuf.getNumber(NumberFormat.Float32BE, 0)
        humidity = Math.round(humidity*100)/100
    }

    /**
     * Reads CO2
     */
    //% weight=87 blockGap=8
    //% block="Read CO2" 
    //% blockId=read_CO2
    export function readCO2(): number{
        return co2
    }

    /**
     * Reads Temperature
     */
    //% weight=87 blockGap=8
    //% block="Read Temperature" 
    //% blockId=read_Temperature
    export function readTemperature(): number{
        return temperature
    }

    /**
     * Reads Humidity
     */
    //% weight=87 blockGap=8
    //% block="Read Humidity" 
    //% blockId=read_Humidity
    export function readHumidity(): number{
        return humidity
    }
}