ucan_json_parser/ucan_json_parser.js

Parse JSON data to uCAN compatible byte streams

let ucan_device_types_array = require('./ucan_device_types.json');
const ucan_frame_data_offset = 0;

module.exports.JSONCommandToByteStream = function(message){
    
    let rx_json = JSON.parse(message);

    console.log(JSON.stringify(rx_json));
    
    let ucan_device_type = ucan_device_types_array.filter((x)=>{
        return x.type == rx_json.type;
    });

    if (ucan_device_type.length > 0)
    {
        let dd = ucan_device_type[0];
        // copose frame header part
        let frame_id = rx_json.id;        
        let buffer = Buffer.alloc(dd.frame_len + ucan_frame_data_offset,0);
        // buffer[0] = rx_json.id;
        // buffer[1] = rx_json.id / 0xFF;
        // copose frame data part
        // 1. find param in device_definition
        let cmd_data = Object.keys(rx_json.signals).map((j) => {
            let mx = dd.signals[j]            
            return {"value":rx_json.signals[j],"sd":mx};
        }); 
        // 2. cast values to bytes
        cmd_data = cmd_data.map(x => {
            e = x.value;
            switch (typeof(e))
            {
                case 'boolean':
                    e  == true ? e = 1 : e = 0;
                    break;
                case 'number':
                    e = e;
                    break;
                default:
                    e = 0; 
            }
            x.value = e;
            return x;    
        });
        // 3. copose data part of the frame                
        cmd_data.forEach(e => {
            buffer[(e.sd.byte + ucan_frame_data_offset)] |= (e.value << e.sd.bit)
        })
        // 4. return frame object        
        let canmsg = { id: frame_id, data: buffer };
        return canmsg;
        // socket_can.sendCANPacket(canmsg);            
    }
};

module.exports.ByteStreamToJSONData = function(message, device_type) {
    // 1. find if device type exist for this id
    let dt = ucan_device_types_array.find((x) => {
        return x.id == device_type;
    });
    //2. if type found map signals     
    if ((dt != undefined) && (message.data.length >= dt.frame_len))
    {
        resp =  {"id": message.id};
        Object.keys(dt.signals).forEach((e) => { 
            let d = (message.data[dt.signals[e].byte + ucan_frame_data_offset] >> dt.signals[e].bit) & (0xFF >> (8-dt.signals[e].size))
            resp[e] = d;
        });   
        return resp;
    }
} 

module.exports.GetDeviceTypes = function(message) 
{
    return ucan_device_types_array;
}