Improve custom function handling (#597)

* In custom function use Array<number> instead of Int8Array

Numbers > 127 shouldn't be used with Int8Array, so to avoid using negative numbers just use Array<number>. Other functions also seem to use this approach.

* Custom function: fix docs and types, add a test

Author: nazar-codethink

ModbusRTU.d.ts

@@ -23,7 +23,7 @@ export class ModbusRTU {
   writeFC16(address: number, dataAddress: number, values: Array<number>, next: NodeStyleCallback<WriteMultipleResult>): void;
   writeFC22(address: number, dataAddress: number, andMask: number, orMask: number, next: NodeStyleCallback<WriteMaskRegisterResult>): void;
 
-  writeCustomFC(address: number, functionCode: number, data: Int8Array, next: NodeStyleCallback<CustomFunctionResult>): void;
+  writeCustomFC(address: number, functionCode: number, data: Array<number>, next: NodeStyleCallback<CustomFunctionResult>): void;
 
   // Connection shorthand API
   connectRTU(path: string, options: SerialPortOptions, next: Function): void;
@@ -68,6 +68,7 @@ export class ModbusRTU {
   writeRegisterEnron(dataAddress: number, value: number): Promise<WriteRegisterResult>;
   writeRegisters(dataAddress: number, values: Array<number> | Buffer): Promise<WriteMultipleResult>; // 16
   maskWriteRegister(dataAddress: number, andMask: number, orMask: number): Promise<WriteMaskRegisterResult>;
+  customFunction(functionCode: number, data: Array<number>): Promise<CustomFunctionResult>;
 
   on(event: 'close', listener: () => unknown): this;
   on(event: 'error', listener: (error: unknown) => unknown): this;
@@ -82,7 +83,7 @@ export interface NodeStyleCallback<T> {
 }
 
 export interface CustomFunctionResult {
-  data: Int8Array;
+  data: Array<number>;
   buffer: Buffer;
 }
 

README.md

@@ -69,6 +69,7 @@ This module has not been tested on every single version of NodeJS. For best resu
 | FC16 "Preset Multiple Registers" | `writeRegisters(addr, valueAry)` |
 | FC22 "Mask Write Register" | `maskWriteRegister(addr, andMask, orMask)` |
 | FC43/14 "Read Device Identification" (supported ports: TCP, RTU) | `readDeviceIdentification(id, obj)` |
+| CustomFC "Custom Function" | `customFunction(functionCode, data)` |
 
 ###### Client Serial:
 

index.js

@@ -309,7 +309,7 @@ function _readFC43(data, modbus, next) {
 
 /**
  * Parse the data for a Modbus -
- * Read Device Identification (FC=43)
+ * "Custom Function Code" (FC=65-72, 100-110)
  *
  * @param {Buffer} data the data buffer to parse.
  * @param {Modbus} modbus the client in case we need to read more device information
@@ -1226,7 +1226,7 @@ class ModbusRTU extends EventEmitter {
      *
      * @param {number} address the slave unit address.
      * @param {number} functionCode the custom function code.
-     * @param {Buffer} data the array of bytes to send.
+     * @param {Array<number>} data the array of bytes to send.
      * @param {Function} next the function to call next.
      */
     writeCustomFC(address, functionCode, data, next) {

ports/testport.js

@@ -274,7 +274,7 @@ class TestPort extends EventEmitter {
             // Custom function code 100 multiplies inputs by 2
             buffer = Buffer.alloc(data.length);
             for (let i = 2; i < (data.length - 2); i++) {
-                buffer.writeUInt8(data.readInt8(i) * 2, i);
+                buffer.writeUInt8(data.readUInt8(i) * 2, i);
             }
         }
 

test/apis/promise.js

@@ -17,6 +17,8 @@ describe("Promise", function() {
             const value = 1;
             const deviceIdCode = 1;
             const objectId = 2;
+            const functionCode = 100;
+            const data = [1, 2, 3];
 
             modbusRTU.open();
             expect(modbusRTU.readCoils(address, arg)).to.be.instanceOf(Promise);
@@ -28,6 +30,7 @@ describe("Promise", function() {
             expect(modbusRTU.writeRegisters(address, [value])).to.be.instanceOf(Promise);
             expect(modbusRTU.readDeviceIdentification(deviceIdCode, objectId)).to.be.instanceOf(Promise);
             expect(modbusRTU.maskWriteRegister(address, arg, arg)).to.be.instanceOf(Promise);
+            expect(modbusRTU.customFunction(functionCode, data)).to.be.instanceOf(Promise);
         });
     });