1 /*
2 * FreeRTOS Modbus Libary: A Modbus serial implementation for FreeRTOS
3 * Copyright (C) 2006 Christian Walter <[email protected]>
4 *
5 * This library is free software; you can redistribute it and/or
6 * modify it under the terms of the GNU Lesser General Public
7 * License as published by the Free Software Foundation; either
8 * version 2.1 of the License, or (at your option) any later version.
9 *
10 * This library is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 * Lesser General Public License for more details.
14 *
15 * You should have received a copy of the GNU Lesser General Public
16 * License along with this library; if not, write to the Free Software
17 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
18 */
19
20
21
22 /* ----------------------- System includes ----------------------------------*/
23 #include "stdlib.h"
24 #include "string.h"
25
26 /* ----------------------- Platform includes --------------------------------*/
27 #include "port.h"
28
29 /* ----------------------- Modbus includes ----------------------------------*/
30 #include "mb.h"
31 #include "mbframe.h"
32 #include "mbproto.h"
33 #include "mbconfig.h"
34
35 /* ----------------------- Defines ------------------------------------------*/
36 #define MB_PDU_FUNC_READ_ADDR_OFF ( MB_PDU_DATA_OFF )
37 #define MB_PDU_FUNC_READ_DISCCNT_OFF ( MB_PDU_DATA_OFF + 2 )
38 #define MB_PDU_FUNC_READ_SIZE ( 4 )
39 #define MB_PDU_FUNC_READ_DISCCNT_MAX ( 0x07D0 )
40
41 /* ----------------------- Static functions ---------------------------------*/
42 eMBException prveMBError2Exception( eMBErrorCode eErrorCode );
43
44 /* ----------------------- Start implementation -----------------------------*/
45
46 #if MB_FUNC_READ_COILS_ENABLED > 0
47
48 eMBException
eMBFuncReadDiscreteInputs(UCHAR * pucFrame,USHORT * usLen)49 eMBFuncReadDiscreteInputs( UCHAR * pucFrame, USHORT * usLen )
50 {
51 USHORT usRegAddress;
52 USHORT usDiscreteCnt;
53 UCHAR ucNBytes;
54 UCHAR *pucFrameCur;
55
56 eMBException eStatus = MB_EX_NONE;
57 eMBErrorCode eRegStatus;
58
59 if( *usLen == ( MB_PDU_FUNC_READ_SIZE + MB_PDU_SIZE_MIN ) )
60 {
61 usRegAddress = ( USHORT )( pucFrame[MB_PDU_FUNC_READ_ADDR_OFF] << 8 );
62 usRegAddress |= ( USHORT )( pucFrame[MB_PDU_FUNC_READ_ADDR_OFF + 1] );
63 usRegAddress++;
64
65 usDiscreteCnt = ( USHORT )( pucFrame[MB_PDU_FUNC_READ_DISCCNT_OFF] << 8 );
66 usDiscreteCnt |= ( USHORT )( pucFrame[MB_PDU_FUNC_READ_DISCCNT_OFF + 1] );
67
68 /* Check if the number of registers to read is valid. If not
69 * return Modbus illegal data value exception.
70 */
71 if( ( usDiscreteCnt >= 1 ) &&
72 ( usDiscreteCnt < MB_PDU_FUNC_READ_DISCCNT_MAX ) )
73 {
74 /* Set the current PDU data pointer to the beginning. */
75 pucFrameCur = &pucFrame[MB_PDU_FUNC_OFF];
76 *usLen = MB_PDU_FUNC_OFF;
77
78 /* First byte contains the function code. */
79 *pucFrameCur++ = MB_FUNC_READ_DISCRETE_INPUTS;
80 *usLen += 1;
81
82 /* Test if the quantity of coils is a multiple of 8. If not last
83 * byte is only partially field with unused coils set to zero. */
84 if( ( usDiscreteCnt & 0x0007 ) != 0 )
85 {
86 ucNBytes = ( UCHAR ) ( usDiscreteCnt / 8 + 1 );
87 }
88 else
89 {
90 ucNBytes = ( UCHAR ) ( usDiscreteCnt / 8 );
91 }
92 *pucFrameCur++ = ucNBytes;
93 *usLen += 1;
94
95 eRegStatus =
96 eMBRegDiscreteCB( pucFrameCur, usRegAddress, usDiscreteCnt );
97
98 /* If an error occured convert it into a Modbus exception. */
99 if( eRegStatus != MB_ENOERR )
100 {
101 eStatus = prveMBError2Exception( eRegStatus );
102 }
103 else
104 {
105 /* The response contains the function code, the starting address
106 * and the quantity of registers. We reuse the old values in the
107 * buffer because they are still valid. */
108 *usLen += ucNBytes;;
109 }
110 }
111 else
112 {
113 eStatus = MB_EX_ILLEGAL_DATA_VALUE;
114 }
115 }
116 else
117 {
118 /* Can't be a valid read coil register request because the length
119 * is incorrect. */
120 eStatus = MB_EX_ILLEGAL_DATA_VALUE;
121 }
122 return eStatus;
123 }
124
125 #endif
126