node-dra818

Control a Dorji DRA818 module on a serial port using node.js.

Use:

const DRA818 = require('dra818');

var radio = new DRA818.Module('/dev/ttyS0', DRA818.VHF);

radio.on(
    'error', (err) => {
        console.log(err);
    }
);

radio.on(
    'change', (setting, value) => {
        console.log(setting + ' changed to ' + value);
    }
);

radio.on(
    'changeError', (setting, value) => {
        console.log('Failed to change ' + setting + ' to ' + value);
        // Reset and retry?
        radio.init();
        radio[setting] = value;
    }
);

radio.open(
    () => {
        try {
            radio.volume = 4;
            radio.narrow = true;
            radio.rxF = 146.52;
            radio.txF = 146.52;
            radio.rxS = 0;
            radio.txS = 0;
            radio.squelch = 0;
        } catch (err) {
            console.log(err);
        }
    }
);

Properties

• DRA818
  • VHF
    • When making a Module, pass this as the 'type' argument if using a DRA818V
  • UHF
    • When making a Module, pass this as the 'type' argument if using a DRA818U or DRA818M
  • TCS_CODES
    • An array of valid CTCSS codes for use with DRA818.Module[rxS, txS]
  • TONE_MAP
    • An array of valid CTCSS frequencies for use with DRA818.Module[rxS, txS]
  • PL_MAP
    • An array of valid Motorla PL tone names for use with DRA818.Module[rxS, txS]
  • DCS_CODES
    • An array of valid CDCSS codes for use with DRA818.Module[rxS, txS]
  • Module(port, type)
    • Module constructor, where 'port' is a serial port (eg. 'COM4' or '/dev/ttyS0') and 'type' is one of DRA818.VHF or DRA818.UHF

Module properties

• volume
  • Integer in the range of 1 - 8
• squelch
  • Integer in the range of 0 - 8
• narrow
  • Boolean, true for 12.5 kHz bandwidth, false for 25 kHz bandwidth
• rxF, txF
  • Float, up to four digits of precision
  • The receive (rxF) or transmit (txF) frequency, in MHz
  • Must be within the frequency range of the DRA818 module
    • DRA818V: 134.0000 to 174.0000
    • DRA818U/M: 400.0000 to 480.0000
• rxS, txS
  • Set the tone squelch or digital code squelch in use on the receive (rxS) or transmit (txS) frequency
  • Integer in the range of 0 - 38
    • 0 to disable CTCSS/CDCSS
    • 1 - 38 to use the corresponding CTCSS code
  • Float
    • Use a particular CTCSS tone, by frequency in Hz; must match one of the tones specified in TONE_MAP (see index.js)
  • String
    • A DCS code (eg. "023I" or "023N"); must match one of the codes specified in DCS_CODES (see index.js)
    • A Motorola PL tone name (eg. "XZ", "M1"); must match one of the codes specified in PL_MAP
• tailtone
  • Boolean, true to turn on the 'tailtone' function, false otherwise
• emphasis
  • Boolean, enable or disable the pre/de-emphasis filter
• highpass
  • Boolean, enable or disable the high-pass filter
• lowpass
  • Boolean, enable or disable the low-pass filter
• rssi
  • Integer in the range of 0 - 255
  • Received Signal Strength Indicator
• rssiInterval
  • Integer >= 0
  • How often to poll the DRA818 module for the RSSI value
  • Set to 0 to disable polling

Module methods

• open(callback)
  • Open the serial port and connect to the module
  • Callback is called with no arguments after the serial port has been opened
• close(callback)
  • Close the serial port
  • Callback receives no arguments
• init()
  • Sends the AT+DMOCONNECT command to the module and expects a +DMOCONNECT:0 response.
  • Use it to 'reset' the module after an error (can't remember if this is necessary)
  • This method is called automatically by DRA818.Module.open()

Module events

• change
  • A setting was changed successfully. Your callback will receive two arguments: the name of the setting, and the new value
• changeError
  • A new setting was not applied successfully. Your callback will receive two arguments: the name of the setting, and the value that you tried to set it to
• rssi
  • The Received Signal Strength Indicator has been read from the module. Your callback will receive one argument: the RSSI value, an integer in the range of 0 - 255
• error
  • Something went wrong; your callback will get an error argument
• disconnect
  • The module has been disconnected
• close
  • The connection to the module has been closed

Notes on the model

I might have used methods and callbacks instead of getters and setters, but it seemed more natural to present the settings as properties instead. If you'd prefer a method/callback interface for changing each setting, or want to be able to issue the DMOSETGROUP or DMOSETFILTER command and change multiple settings all in one shot, let me know and I'll look at adding it.

The two drawbacks of the current model are that:

• If a problem is encountered when applying a setting to the radio module, you won't find out about it until a 'changeError' event is fired. It might be preferable to call, say, radio.setRxFrequency(value, callback), and then react to an error, if present, in your callback. However, this module makes an effort to prevent you from supplying the DRA818 with settings that could produce an error - so barring problems with your DRA818 itself or trouble with the serial connection, this shouldn't happen.
• The DRA818 takes several settings all at once via the AT+DMOSETGROUP and AT+DMOSETFILTER commmands. In order to change the receive frequency, we must send the desired bandwidth setting, receive frequency, transmit frequency, rx and tx CTCSS/CDCSS codes, and squelch level in one line. If you change several of these settings in a row, the same command, with slight variation, will be sent several times. This happens quickly enough to not be a problem, but it's inefficient and that bugs me. I may add some additional methods to deal with this, but it hardly seems worthwhile.