修复连接PLC的问题

Cigarette/PLC/PLCDevice.cpp

@@ -11,22 +11,30 @@ modbus_t * g_modbus = NULL;		//Modbus TCP
 
 bool PLCDevice::init_plc(PLCDevice* PLCptr)
 {
-	const char* comport= g_sys_conf.ComPort.data();
+	// modbus_connect() 建立连接，成功返回0，错误返回-1
+	// modbus_new_rtu 生成RTU的连接，建立成功则返回指向modbus_t结构的指针，否则将返回NULL/0
+
+	const char* comport = g_sys_conf.ComPort.data();
 	qDebug() << "COM:" << comport;
 	//连接PLC
 	g_modbus = modbus_new_rtu(comport, 9600, 'N', 8, 1);
-	modbus_set_debug(g_modbus, 0);
+	modbus_set_debug(g_modbus, 0);	// 用flag设置debug调试标志位，flag=1时显示modbus消息的字节
+	modbus_set_response_timeout(g_modbus, 1, 0);	// 设置响应超时
+	modbus_connect(g_modbus);
+	modbus_set_slave(g_modbus, 1);	// 设置从站id
 
-	modbus_set_response_timeout(g_modbus, 1, 0);
-	if (g_modbus && modbus_connect(g_modbus) == -1) {
+	uint8_t data;
+	int ret = modbus_read_bits(g_modbus, 30000, 1, &data);
+	if (g_modbus && ret == -1) {
 		PLCptr->g_plc_ok = false;
 	}
 	else {
-		modbus_set_slave(g_modbus, 1);
+		
 		PLCptr->g_plc_ok = true;
 	}
 	return true;
 }
+
 bool PLCDevice::disconnect_plc(void)
 {
 	if(g_modbus)
@@ -36,6 +44,7 @@ bool PLCDevice::disconnect_plc(void)
 	}
 	return true;
 }
+
 int PLCDevice::write_bit_2_plc(int addr, int value)
 {
 	if (g_plc_ok)