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Modbus RTU Exception Forwarding (#29)

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Add checking for Modbus exception codes returned by RTU slaves

These PDUs are now forwarded to the TCP client.
This commit is contained in:
dwyer-employee 2018-03-26 05:12:43 -05:00 committed by Victor Antonovich
parent fb3d6d6489
commit 8f2ccf1ec0
2 changed files with 35 additions and 1 deletions
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30
src/conn.c
View File

@ -438,11 +438,26 @@ conn_loop(void)
#ifdef DEBUG
logw(5, "tty: response read (total %d bytes, offset %d bytes)", tty.ptrbuf, tty.rxoffset);
#endif
/* Check if there is enough data for an error response
and if the error flag is set in the function code */
if ((tty.ptrbuf >= MB_ERR_LEN) && (tty.rxbuf[tty.rxoffset+TTY_FCODE_IDX] & TTY_ERR_MASK))
{
/* This is an error response, set the length to
5 (1 + 1 + 1 + 2) = Slave Address + Function Code + Error Code + CRC */
tty.ptrbuf = MB_ERR_LEN;
}
if (tty.ptrbuf >= MB_MIN_LEN &&
modbus_crc_correct(tty.rxbuf + tty.rxoffset, tty.ptrbuf - tty.rxoffset))
{ /* received response is correct, make OpenMODBUS response */
#ifdef DEBUG
logw(5, "tty: response is correct");
// Optionally print the correct packet data
t[0] = '\0';
for (i = 0; i < tty.ptrbuf; i++) {
sprintf(v,"[%2.2x]", tty.rxbuf[i]);
strncat(t, v, 256);
}
logw(9, "tty: (%s)", t);
#endif
(void)memcpy((void *)(actconn->buf + HDRSIZE),
(void *)(tty.rxbuf + tty.rxoffset), tty.ptrbuf - CRCSIZE - tty.rxoffset);
@ -661,11 +676,26 @@ conn_loop(void)
#ifdef DEBUG
logw(5, "tty: response read (total %d bytes, offset %d bytes)", tty.ptrbuf, tty.rxoffset);
#endif
/* Check if there is enough data for an error response
and if the error flag is set in the function code */
if ((tty.ptrbuf >= MB_ERR_LEN) && (tty.rxbuf[tty.rxoffset+TTY_FCODE_IDX] & TTY_ERR_MASK))
{
/* This is an error response, set the length to
5 (1 + 1 + 1 + 2) = Slave Address + Function Code + Error Code + CRC */
tty.ptrbuf = MB_ERR_LEN;
}
if (tty.ptrbuf >= MB_MIN_LEN &&
modbus_crc_correct(tty.rxbuf + tty.rxoffset, tty.ptrbuf - tty.rxoffset))
{ /* received response is correct, make OpenMODBUS response */
#ifdef DEBUG
logw(5, "tty: response is correct");
// Optional print the correct packet data
t[0] = '\0';
for (i = 0; i < tty.ptrbuf; i++) {
sprintf(v,"[%2.2x]", tty.rxbuf[i]);
strncat(t, v, 256);
}
logw(9, "(%s)", t);
#endif
(void)memcpy((void *)(actconn->buf + HDRSIZE),
(void *)(tty.rxbuf + tty.rxoffset), tty.ptrbuf - CRCSIZE - tty.rxoffset);

6
src/modbus.h
View File

@ -47,6 +47,7 @@
*/
#define MB_EX_LEN 3
#define MB_MIN_LEN 4
#define MB_ERR_LEN 5
#define MB_MAX_LEN 256
/*
@ -79,7 +80,10 @@
#define MB_UNIT_ID 6 /* unit identifier */
#define MB_FCODE 7 /* function code */
#define MB_DATA 8 /* MODBUS data */
#define TTY_FCODE_IDX 1 /* The index of the function code in a RTU packet */
#define TTY_ERR_MASK 0x80 /* The MSB of the response function code indicates an error response */
/*
* Exception codes
*/