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modbus: add support for defining custom functions

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Enables support for custom function codes. Modbus specification allows
vendor specific function codes in the range 65-72 & 100-110 [1] and this
feature allows users to implement custom logic for those codes.
Additionally, since the Zephyr Modbus stack doesn't implement all defined
Modbus fcs this feature allows users to add support for codes outside the
basic register reading / writing functionality offered by Zephyr.

Custom function codes can be added on a per-interface basis and the handler
structures are allocated by the caller.

[1]: https://modbus.org/docs/Modbus_Application_Protocol_V1_1b.pdf

Signed-off-by: Henrik Lindblom <henrik.lindblom@vaisala.com>
This commit is contained in:
Henrik Lindblom 2023-03-04 08:38:45 +02:00 committed by Carles Cufí
parent 121d051c9a
commit 01757cfd32
4 changed files with 158 additions and 17 deletions
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87
include/zephyr/modbus/modbus.h
View file

@ -31,7 +31,7 @@
#define ZEPHYR_INCLUDE_MODBUS_H_
#include <zephyr/drivers/uart.h>
#include <zephyr/sys/slist.h>
#ifdef __cplusplus
extern "C" {
#endif
@ -41,6 +41,22 @@ extern "C" {
/** Length of MBAP Header plus function code */
#define MODBUS_MBAP_AND_FC_LENGTH (MODBUS_MBAP_LENGTH + 1)
/** @name Modbus exception codes
* @{
*/
/* Modbus exception codes */
#define MODBUS_EXC_NONE 0
#define MODBUS_EXC_ILLEGAL_FC 1
#define MODBUS_EXC_ILLEGAL_DATA_ADDR 2
#define MODBUS_EXC_ILLEGAL_DATA_VAL 3
#define MODBUS_EXC_SERVER_DEVICE_FAILURE 4
#define MODBUS_EXC_ACK 5
#define MODBUS_EXC_SERVER_DEVICE_BUSY 6
#define MODBUS_EXC_MEM_PARITY_ERROR 8
#define MODBUS_EXC_GW_PATH_UNAVAILABLE 10
#define MODBUS_EXC_GW_TARGET_FAILED_TO_RESP 11
/** @} */
/**
* @brief Frame struct used internally and for raw ADU support.
*/
@ -384,6 +400,57 @@ int modbus_iface_get_by_name(const char *iface_name);
typedef int (*modbus_raw_cb_t)(const int iface, const struct modbus_adu *adu,
void *user_data);
/**
* @brief Custom function code handler function signature.
*
* Modbus allows user defined function codes which can be used to extend
* the base protocol. These callbacks can also be used to implement
* function codes currently not supported by Zephyr's Modbus subsystem.
*
* If an error occurs during the handling of the request, the handler should
* signal this by setting excep_code to a modbus exception code.
*
* User data pointer can be used to pass state between subsequent calls to
* the handler.
*
* @param iface Modbus interface index
* @param rx_adu Pointer to the received ADU struct
* @param tx_adu Pointer to the outgoing ADU struct
* @param excep_code Pointer to possible exception code
* @param user_data Pointer to user data
*
* @retval true If response should be sent, false otherwise
*/
typedef bool (*modbus_custom_cb_t)(const int iface,
const struct modbus_adu *const rx_adu,
struct modbus_adu *const tx_adu,
uint8_t *const excep_code,
void *const user_data);
/** @cond INTERNAL_HIDDEN */
/**
* @brief Custom function code definition.
*/
struct modbus_custom_fc {
sys_snode_t node;
modbus_custom_cb_t cb;
void *user_data;
uint8_t fc;
uint8_t excep_code;
};
/** @endcond INTERNAL_HIDDEN */
/**
* @brief Helper macro for initializing custom function code structs
*/
#define MODBUS_CUSTOM_FC_DEFINE(name, user_cb, user_fc, userdata) \
static struct modbus_custom_fc modbus_cfg_##name = { \
.cb = user_cb, \
.user_data = userdata, \
.fc = user_fc, \
.excep_code = MODBUS_EXC_NONE, \
}
/**
* @brief Modbus interface mode
*/
@ -535,6 +602,24 @@ void modbus_raw_set_server_failure(struct modbus_adu *adu);
*/
int modbus_raw_backend_txn(const int iface, struct modbus_adu *adu);
/**
* @brief Register a user-defined function code handler.
*
* The Modbus specification allows users to define standard function codes
* missing from Zephyr's Modbus implementation as well as add non-standard
* function codes in the ranges 65 to 72 and 100 to 110 (decimal), as per
* specification.
*
* This function registers a new handler at runtime for the given
* function code.
*
* @param iface Modbus client interface index
* @param custom_fc User defined function code and callback pair
*
* @retval 0 on success
*/
int modbus_register_user_fc(const int iface, struct modbus_custom_fc *custom_fc);
#ifdef __cplusplus
}
#endif

36
subsys/modbus/modbus_core.c
View file

@ -211,6 +211,14 @@ static struct modbus_context *modbus_init_iface(const uint8_t iface)
return ctx;
}
static int modbus_user_fc_init(struct modbus_context *ctx, struct modbus_iface_param param)
{
sys_slist_init(&ctx->user_defined_cbs);
LOG_DBG("Initializing user-defined function code support.");
return 0;
}
int modbus_init_server(const int iface, struct modbus_iface_param param)
{
struct modbus_context *ctx = NULL;
@ -236,6 +244,12 @@ int modbus_init_server(const int iface, struct modbus_iface_param param)
ctx->client = false;
if (modbus_user_fc_init(ctx, param) != 0) {
LOG_ERR("Failed to init MODBUS user defined function codes");
rc = -EINVAL;
goto init_server_error;
}
switch (param.mode) {
case MODBUS_MODE_RTU:
case MODBUS_MODE_ASCII:
@ -278,6 +292,28 @@ init_server_error:
return rc;
}
int modbus_register_user_fc(const int iface, struct modbus_custom_fc *custom_fc)
{
struct modbus_context *ctx = modbus_get_context(iface);
if (!custom_fc) {
LOG_ERR("Provided function code handler was NULL");
return -EINVAL;
}
if (custom_fc->fc & BIT(7)) {
LOG_ERR("Function codes must have MSB of 0");
return -EINVAL;
}
custom_fc->excep_code = MODBUS_EXC_NONE;
LOG_DBG("Registered new custom function code %d", custom_fc->fc);
sys_slist_append(&ctx->user_defined_cbs, &custom_fc->node);
return 0;
}
int modbus_init_client(const int iface, struct modbus_iface_param param)
{
struct modbus_context *ctx = NULL;

14
subsys/modbus/modbus_internal.h
View file

@ -55,18 +55,6 @@
#define MODBUS_FC08_SUBF_SERVER_MSG_CTR 14
#define MODBUS_FC08_SUBF_SERVER_NO_RESP_CTR 15
/* Modbus exception codes */
#define MODBUS_EXC_NONE 0
#define MODBUS_EXC_ILLEGAL_FC 1
#define MODBUS_EXC_ILLEGAL_DATA_ADDR 2
#define MODBUS_EXC_ILLEGAL_DATA_VAL 3
#define MODBUS_EXC_SERVER_DEVICE_FAILURE 4
#define MODBUS_EXC_ACK 5
#define MODBUS_EXC_SERVER_DEVICE_BUSY 6
#define MODBUS_EXC_MEM_PARITY_ERROR 8
#define MODBUS_EXC_GW_PATH_UNAVAILABLE 10
#define MODBUS_EXC_GW_TARGET_FAILED_TO_RESP 11
/* Modbus RTU (ASCII) constants */
#define MODBUS_COIL_OFF_CODE 0x0000
#define MODBUS_COIL_ON_CODE 0xFF00
@ -142,6 +130,8 @@ struct modbus_context {
uint16_t mbs_server_msg_ctr;
uint16_t mbs_noresp_ctr;
#endif
/* A linked list of function code, handler pairs */
sys_slist_t user_defined_cbs;
/* Unit ID */
uint8_t unit_id;

38
subsys/modbus/modbus_server.c
View file

@ -926,6 +926,38 @@ static bool mbs_fc16_hregs_write(struct modbus_context *ctx)
return true;
}
static bool mbs_try_user_fc(struct modbus_context *ctx, uint8_t fc)
{
struct modbus_custom_fc *p;
LOG_DBG("Searching for custom Modbus handlers for code %u", fc);
SYS_SLIST_FOR_EACH_CONTAINER(&ctx->user_defined_cbs, p, node) {
if (p->fc == fc) {
int iface = modbus_iface_get_by_ctx(ctx);
bool rval;
LOG_DBG("Found custom handler");
p->excep_code = MODBUS_EXC_NONE;
rval = p->cb(iface, &ctx->rx_adu, &ctx->tx_adu, &p->excep_code,
p->user_data);
if (p->excep_code != MODBUS_EXC_NONE) {
LOG_INF("Custom handler failed with code %d", p->excep_code);
mbs_exception_rsp(ctx, p->excep_code);
}
return rval;
}
}
LOG_ERR("Function code 0x%02x not implemented", fc);
mbs_exception_rsp(ctx, MODBUS_EXC_ILLEGAL_FC);
return true;
}
bool modbus_server_handler(struct modbus_context *ctx)
{
bool send_reply = false;
@ -945,6 +977,7 @@ bool modbus_server_handler(struct modbus_context *ctx)
}
if (addr != 0 && addr != ctx->unit_id) {
LOG_DBG("Unit ID doesn't match %u != %u", addr, ctx->unit_id);
update_noresp_ctr(ctx);
return false;
}
@ -995,10 +1028,7 @@ bool modbus_server_handler(struct modbus_context *ctx)
break;
default:
LOG_ERR("Function code 0x%02x not implemented", fc);
mbs_exception_rsp(ctx, MODBUS_EXC_ILLEGAL_FC);
send_reply = true;
break;
send_reply = mbs_try_user_fc(ctx, fc);
}
if (addr == 0) {