56 lines
1.8 KiB
JavaScript
56 lines
1.8 KiB
JavaScript
'use strict';
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const Stampit = require('stampit');
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const Put = require('put');
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module.exports = Stampit()
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.init(function () {
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const FC = 3;
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let init = () => {
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this.log.debug('initiating read holding registers request handler.');
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this.responseDelay = this.responseDelay || 0;
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this.setRequestHandler(FC, onRequest);
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};
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let _onRequest = (pdu, cb) => {
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if (pdu.length !== 5) {
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this.log.warn('wrong pdu length.');
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cb(Put().word8(0x83).word8(0x02).buffer());
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} else {
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const fc = pdu.readUInt8(0);
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const start = pdu.readUInt16BE(1);
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const byteStart = start * 2;
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const quantity = pdu.readUInt16BE(3);
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this.emit('readHoldingRegistersRequest', byteStart, quantity);
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let mem = this.getHolding();
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if (!quantity || byteStart + (quantity * 2) > mem.length) {
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this.log.debug('request outside register boundaries.');
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cb(Put().word8(0x83).word8(0x02).buffer());
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return;
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}
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let response = Put().word8(0x03).word8(quantity * 2);
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for (let i = byteStart; i < byteStart + (quantity * 2); i += 2) {
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response.word16be(mem.readUInt16BE(i));
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}
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this.log.debug('finished read holding register request.');
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cb(response.buffer());
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}
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};
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let onRequest = (pdu, cb) => {
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if (this.responseDelay) {
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setTimeout(_onRequest, this.responseDelay, pdu, cb);
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} else {
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setImmediate(_onRequest, pdu, cb);
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}
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};
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init();
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});
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