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Modbus read device id

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This commit is contained in:
mj 2021-12-22 17:12:14 +01:00
parent 6dbbccec33
commit 0ed535bb76
3 changed files with 119 additions and 40 deletions
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16
fw/Core/Inc/modbus.h
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@ -40,6 +40,7 @@
#include "stdint.h"
#include "stddef.h"
#include "string.h"
/*
* Defines & macros
@ -49,13 +50,22 @@
#define MODBUS_DEFAULT_SLAVE_ADDRESS 254 /* 255 may be used for bridge device */
/* minimal frame length is 4 bytes: 1 B slave address, 1 B function code, 2 B CRC */
#define MODBUS_MINIMAL_FRAME_LEN 4
#define MODBUS_MINIMAL_READWRITE_LEN 4
#define MODBUS_MINIMAL_WRITE_MULTIPLE_LEN 5
#define MODBUS_READ_DEVICE_ID_REQUEST_LEN 4
#define MODBUS_READ_DEVICE_ID_RESPONSE_HEADER_LEN 4
#define MODBUS_READ_DEVICE_ID_RESPONSE_OFFSET 3
#define MODBUS_MAX_RTU_FRAME_SIZE 256
#define MODBUS_BUFFER_SIZE MODBUS_MAX_RTU_FRAME_SIZE /* alias */
#define MODBUS_ERROR_FLAG 0x80
#define MODBUS_MAX_REGISTERS 125
/* read device id constants */
#define MODBUS_MEI 0x0E
#define MODBUS_DEVICE_ID_INDIVIDUAL_ACCESS_FLAG 0x80
#define MODBUS_MORE_FOLLOWS 0xFF
#define MODBUS_NO_MORE_FOLLOWS 0x00
#define MODBUS_BASIC_OBJECT_COUNT 3
#define MODBUS_REGULAR_OBJECT_COUNT 7
/*
* Return values
@ -141,6 +151,10 @@ typedef struct {
int16_t input_registers_signed[MODBUS_MAX_REGISTERS];
int16_t holding_registers_signed[MODBUS_MAX_REGISTERS];
};
/* process device id */
uint8_t read_device_id_code;
uint8_t object_id;
} modbus_transaction_t;
typedef enum {
@ -158,7 +172,7 @@ typedef enum {
MODBUS_CONFORMITY_BASIC = 1,
MODBUS_CONFORMITY_REGULAR = 2,
MODBUS_CONFORMITY_EXTENDED = 3,
MODBUS_INDIVIDUAL_ACCESS = 4
MODBUS_INDIVIDUAL_ACCESS = 4 /* not actually part of conformity, but I'll keep it here anyway */
} modbus_conformity_level_t;
/* Device ID datatypes */

4
fw/Core/Src/main.c
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@ -231,10 +231,10 @@ int main(void)
rgbled_set_color(RGBLED_WHITE); /* white color indicates init process */
/* Fill device ID struct */
device_id.object_name.VendorName = "NeoMokoshTron Corp.";
device_id.object_name.VendorName = "Veles Labs";
device_id.object_name.ProductCode = "124C41";
device_id.object_name.MajorMinorRevision = "1.2";
device_id.object_name.VendorUrl = "https://neomokoshtron.com";
device_id.object_name.VendorUrl = "https://veles-labs.com";
device_id.object_name.ProductName = "SensCO2";
device_id.object_name.ModelName = "Hugo";
modbus_slave_init_device_id(&device_id);

139
fw/Core/Src/modbus.c
View File

@ -54,54 +54,114 @@ uint16_t modbus_CRC16(const uint8_t *buf, int len)
* Private functions
*/
static uint8_t modbus_fill_device_id_objects(uint8_t *buffer, modbus_transaction_t *transaction)
{
/* we assume buffer is 256 - MODBUS_READ_DEVICE_ID_RESPONSE_HEADER_LEN = 252 bytes long */
/* find out how many objects we copy to buffer */
int len;
uint8_t object_index = transaction->object_id;
uint8_t object_count;
uint8_t more_follows = MODBUS_NO_MORE_FOLLOWS;
uint8_t next_object_id;
uint8_t last_object;
const uint8_t max_len = 256 - MODBUS_READ_DEVICE_ID_RESPONSE_HEADER_LEN;
/* last object index */
if (transaction->read_device_id_code == MODBUS_CONFORMITY_BASIC) {
last_object = MODBUS_BASIC_OBJECT_COUNT;
} else if (transaction->read_device_id_code == MODBUS_CONFORMITY_REGULAR) {
last_object = MODBUS_REGULAR_OBJECT_COUNT;
/* extended not implemented */
// } else if (transaction->read_device_id_code == MODBUS_CONFORMITY_EXTENDED){
// last_object = MODBUS_EXTENDED_OBJECT_COUNT;
} else {
/* fallback: regular */
last_object = MODBUS_REGULAR_OBJECT_COUNT;
}
last_object--; // we need index
/* copy as many objects as possible */
do {
/* copy object */
int object_len = strlen(modbus_device_id->object_id[object_index]);
if (len + object_len + 2 > max_len) {
more_follows = MODBUS_MORE_FOLLOWS;
next_object_id = object_index;
break;
}
/* offset is for "more follows", "next object id", "object count" */
buffer[MODBUS_READ_DEVICE_ID_RESPONSE_OFFSET + len++] = object_index;
buffer[MODBUS_READ_DEVICE_ID_RESPONSE_OFFSET + len++] = object_len;
/* note that string copied to buffer is not null-terminated */
strncpy((char*)(buffer + len), (char*)modbus_device_id->object_id[object_index++], object_len);
len += object_len;
object_count++;
} while (object_index < last_object);
buffer[0] = more_follows;
buffer[1] = next_object_id;
buffer[2] = object_count;
return MODBUS_READ_DEVICE_ID_RESPONSE_OFFSET + len;
}
/* here we assume buffer has minimal size of MODBUS_MAX_RTU_FRAME_SIZE;
* this function is private, so hopefully it's going to be ok */
static int8_t modbus_transaction_to_buffer(uint8_t *buffer, uint8_t *msg_len, modbus_transaction_t *transaction)
{
uint16_t crc16;
uint8_t byte_count;
uint8_t buffer_pos = 0;
// TODO use relative indices (increments) instead of absolute
buffer[0] = modbus_slave_address;
buffer[1] = transaction->function_code;
buffer[buffer_pos++] = modbus_slave_address;
buffer[buffer_pos++] = transaction->function_code;
*msg_len = 5;
if (transaction->function_code & MODBUS_ERROR_FLAG) {
/* sending error reply */
buffer[2] = transaction->exception;
buffer[buffer_pos++] = transaction->exception;
} else {
switch (transaction->function_code) {
case MODBUS_READ_HOLDING_REGISTERS:
case MODBUS_READ_INPUT_REGISTERS:
byte_count = transaction->register_count * 2;
buffer[2] = byte_count;
buffer[buffer_pos++] = byte_count;
*msg_len = byte_count + 5;
for (int i = 0; i < transaction->register_count; i++) {
// TODO endianness handling
/* buffer16b is alias for both holding and input register buffers */
buffer[3 + 2*i] = transaction->buffer16b[i] >> 8;
buffer[4 + 2*i] = transaction->buffer16b[i] & 0xff;
buffer[buffer_pos++] = transaction->buffer16b[i] >> 8;
buffer[buffer_pos++] = transaction->buffer16b[i] & 0xff;
}
break;
case MODBUS_WRITE_SINGLE_REGISTER:
buffer[2] = (uint8_t) (transaction->register_address >> 8);
buffer[3] = (uint8_t) transaction->register_address;
buffer[4] = (uint8_t) (transaction->holding_registers[0] >> 8);
buffer[5] = (uint8_t) transaction->holding_registers[0];
*msg_len = 8;
buffer[buffer_pos++] = (uint8_t) (transaction->register_address >> 8);
buffer[buffer_pos++] = (uint8_t) transaction->register_address;
buffer[buffer_pos++] = (uint8_t) (transaction->holding_registers[0] >> 8);
buffer[buffer_pos++] = (uint8_t) transaction->holding_registers[0];
*msg_len = 8; /* includes 2 bytes for CRC */
break;
case MODBUS_WRITE_MULTIPLE_REGISTERS:
buffer[2] = (uint8_t) (transaction->register_address >> 8);
buffer[3] = (uint8_t) transaction->register_address;
buffer[4] = (uint8_t) (transaction->register_count >> 8);
buffer[5] = (uint8_t) transaction->register_count;
*msg_len = 8;
buffer[buffer_pos++] = (uint8_t) (transaction->register_address >> 8);
buffer[buffer_pos++] = (uint8_t) transaction->register_address;
buffer[buffer_pos++] = (uint8_t) (transaction->register_count >> 8);
buffer[buffer_pos++] = (uint8_t) transaction->register_count;
*msg_len = 8; /* includes 2 bytes for CRC */
break;
case MODBUS_READ_DEVICE_IDENTIFICATION:
/* MEI type */
buffer[buffer_pos++] = MODBUS_MEI;
/* read device id */
buffer[buffer_pos++] = transaction->read_device_id_code;
/* conformity level */
buffer[buffer_pos++] = modbus_device_id->conformity_level;
/* fill buffer with as many objects as possible */
*msg_len = modbus_fill_device_id_objects(buffer+buffer_pos, transaction);
*msg_len += 7; /* includes 2 bytes for CRC */
break;
}
}
crc16 = modbus_CRC16(buffer, *msg_len - 2); /* last two bytes is the checksum itself */
buffer[*msg_len - 2] = crc16 & 0xff;
buffer[*msg_len - 1] = crc16 >> 8;
crc16 = modbus_CRC16(buffer, buffer_pos); /* last two bytes is the checksum itself */
buffer[buffer_pos++] = crc16 & 0xff;
buffer[buffer_pos++] = crc16 >> 8;
}
static int8_t modbus_process_device_id_request(const uint8_t *buffer, int len, modbus_transaction_t *transaction)
@ -118,6 +178,7 @@ static int8_t modbus_process_device_id_request(const uint8_t *buffer, int len, m
return MODBUS_ERROR;
}
if (modbus_device_id == NULL) {
/* modbus_device_id not initialized; user should use modbus_slave_init_device_id() first */
transaction->exception = MODBUS_EXCEPTION_ILLEGAL_DEVICE_ID_CODE;
return MODBUS_OK;
}
@ -128,7 +189,7 @@ static int8_t modbus_process_device_id_request(const uint8_t *buffer, int len, m
/* next byte should be MEI = 0x0E */
MEI_type = buffer[buffer_pos++];
if (MEI_type != MODBUS_MEI) {
/* invalid MEI, ignore. I have no idea what this MEI does, but it should always be 0x0E */
/* invalid MEI, ignore. I have no idea what MEI does, but it should always be 0x0E */
return MODBUS_ERROR;
}
/* next byte is read device id code */
@ -138,25 +199,20 @@ static int8_t modbus_process_device_id_request(const uint8_t *buffer, int len, m
transaction->exception = MODBUS_EXCEPTION_ILLEGAL_DEVICE_ID_CODE;
return MODBUS_OK;
}
/* cross-check with conformity level (mask 0x80 bit, which only specified individual access) */
if (read_device_id_code == MODBUS_INDIVIDUAL_ACCESS) {
individual_object_access = 1;
} else {
/* check conformity level */
conformity_masked = modbus_device_id->conformity_level & ~0x80;
if (read_device_id_code > conformity_masked) {
/* requested conformity higher than allowed */
read_device_id_code = conformity_masked;
}
}
transaction->read_device_id_code = read_device_id_code;
/* next byte is object id */
object_id = buffer[buffer_pos++];
transaction->object_id = object_id;
if (object_id > MODBUS_DEVICE_ID_OBJECT_NUM) {
/* illegal object ID */
transaction->exception = MODBUS_EXCEPTION_ILLEGAL_DATA_ADDRESS;
return MODBUS_OK;
}
/* Message processed; create reply message */
/* Message processed */
return MODBUS_OK;
}
/* returns ERROR only when no response to master is needed */
@ -207,7 +263,7 @@ static int8_t modbus_process_read_write_request(const uint8_t *buffer, int len,
case MODBUS_READ_COILS:
case MODBUS_READ_INPUT_REGISTERS:
case MODBUS_READ_HOLDING_REGISTERS:
if (len < (MODBUS_MINIMAL_FRAME_LEN + 2)) {
if (len < MODBUS_MINIMAL_READWRITE_LEN) {
/* buffer too short to contain everything we need */
return MODBUS_ERROR;
}
@ -219,11 +275,17 @@ static int8_t modbus_process_read_write_request(const uint8_t *buffer, int len,
} else {
/* Write multiple registers */
transaction->register_count = (buffer[buffer_pos++] << 8) | buffer[buffer_pos++];
if (len < MODBUS_MINIMAL_WRITE_MULTIPLE_LEN) {
return MODBUS_ERROR;
}
byte_count = buffer[buffer_pos++];
if (transaction->register_count > 123 || 2*transaction->register_count != byte_count) {
/* Max number of register is defined by Modbus_Application_Protocol_V1_1b, section 6.12 */
transaction->exception = MODBUS_EXCEPTION_ILLEGAL_REGISTER_QUANTITY;
} else {
if (len < MODBUS_MINIMAL_WRITE_MULTIPLE_LEN + byte_count) {
return MODBUS_ERROR;
}
for (uint8_t i = 0; i < transaction->register_count; i++) {
transaction->holding_registers[i] = (buffer[buffer_pos++] << 8) | buffer[buffer_pos++];
}
@ -297,9 +359,7 @@ int8_t modbus_slave_process_msg(const uint8_t *buffer, int len)
/* transaction holds message context and content:
* it wraps all necessary buffers and variables */
modbus_transaction_t transaction;
int8_t callback_result;
uint8_t buffer_pos = 0;
uint8_t byte_count;
if (len < MODBUS_MINIMAL_FRAME_LEN) {
/* frame too short; return error (no reply needed) */
@ -316,24 +376,28 @@ int8_t modbus_slave_process_msg(const uint8_t *buffer, int len)
uint8_t address = buffer[buffer_pos++];
transaction.broadcast = (address == MODBUS_BROADCAST_ADDR);
if (address != modbus_slave_address && transaction.broadcast != 1) {
/* Message is not for us */
/* Message is not for us (no reply needed) */
return MODBUS_OK;
}
/* get function code */
transaction.function_code = buffer[buffer_pos++];
transaction.exception = 0;
uint8_t request_processing_error;
uint8_t request_processing_result;
if (transaction.function_code == MODBUS_READ_DEVICE_IDENTIFICATION) {
request_processing_error = modbus_process_device_id_request(buffer + buffer_pos, len - buffer_pos, &transaction);
/* Read device ID request is quite complicated, therefore it has its own processing function */
request_processing_result = modbus_process_device_id_request(buffer + buffer_pos, len - buffer_pos, &transaction);
} else {
request_processing_error = modbus_process_read_write_request(buffer + buffer_pos, len - buffer_pos, &transaction);
/* process other requests: input register read, holding register read/write */
request_processing_result = modbus_process_read_write_request(buffer + buffer_pos, len - buffer_pos, &transaction);
}
uint8_t msg_len;
/* reply only if request was processed successfully and message was not broadcast */
if (request_processing_error == 0 && transaction.broadcast == 0) {
if (request_processing_result == MODBUS_OK && transaction.broadcast == 0) {
modbus_transaction_to_buffer(modbus_buffer, &msg_len, &transaction);
/* send reply */
modbus_transmit_function(modbus_buffer, msg_len);
}
return MODBUS_OK;
}
int8_t modbus_slave_init_device_id(modbus_device_id_t *device_id)
@ -362,4 +426,5 @@ int8_t modbus_slave_init_device_id(modbus_device_id_t *device_id)
/* we support both stream and individual access to objects */
device_id->conformity_level |= MODBUS_DEVICE_ID_INDIVIDUAL_ACCESS_FLAG;
modbus_device_id = device_id;
return MODBUS_OK;
}