From 66154d6c48102460a0661169fc17e733fa4c3a5e Mon Sep 17 00:00:00 2001
From: Fernando Herrero <alphp@users.noreply.github.com>
Date: Tue, 12 Oct 2021 23:23:53 +0200
Subject: [PATCH] sendRequest fix error detection

---
 composer.json     |  2 +-
 src/ModbusRTU.php | 11 ++++-------
 2 files changed, 5 insertions(+), 8 deletions(-)

diff --git a/composer.json b/composer.json
index 1e6b580..c9256d4 100644
--- a/composer.json
+++ b/composer.json
@@ -1,6 +1,6 @@
 {
     "name": "fawno/modbus",
-    "version": "0.1.0",
+    "version": "0.1.1",
     "description": "Modbus RTU serial protocol in PHP",
     "keywords": ["Modbus RTU", "DDS238"],
     "license": "MIT",
diff --git a/src/ModbusRTU.php b/src/ModbusRTU.php
index c8dbdf6..b6af7c4 100644
--- a/src/ModbusRTU.php
+++ b/src/ModbusRTU.php
@@ -12,9 +12,6 @@ class ModbusRTU extends SerialDio {
 		public const MODBUS_ADU = 'C1station/C1function/C*data/';
 		public const MODBUS_ERROR = 'C1station/C1error/C1exception/';
 
-		private const MODBUS_REQUEST = 'C2n2';
-		//public const MODBUS_RESPONSE = 'C1station/C1function/C1count/n*records/';
-
 		protected $_options = [
 			'data_rate' => 9600,
 			'data_bits' => 8,
@@ -434,10 +431,6 @@ public function sendRequest (string $request) {
 				throw new Exception(sprintf('Response lenght too short: "%s"', bin2hex($response)), -1);
 			}
 
-			if (substr($response, -2) != $this->crc16(substr($response, 0, -2))) {
-				throw new Exception('Error check fails', -2);
-			}
-
 			$adu_request = unpack(self::MODBUS_ADU, $request);
 			$adu_response = unpack(self::MODBUS_ERROR, $response);
 			if ($adu_request['function'] != $adu_response['error']) {
@@ -449,6 +442,10 @@ public function sendRequest (string $request) {
 				}
 			}
 
+			if (substr($response, -2) != $this->crc16(substr($response, 0, -2))) {
+				throw new Exception(sprintf('Error check fails: "%s"', bin2hex($response)), -2);
+			}
+
 			return $response;
 		}
 	}