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Added basic modbus implementation

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This commit is contained in:
dooku 2021-08-16 23:04:45 +02:00
parent 5f1a9295e2
commit 6830fabbd3
5 changed files with 423 additions and 11 deletions
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2
fw/Core/Inc/main.h
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@ -52,6 +52,7 @@ extern "C" {
#include "scd4x.h"
#include "sht4x.h"
#include "sps30.h"
#include "modbus.h"
/* USER CODE END Includes */
/* Exported types ------------------------------------------------------------*/
@ -98,7 +99,6 @@ void Error_Handler(void);
/* USER CODE BEGIN Private defines */
#define MEASUREMENT_PERIOD_MS 600000
extern uint8_t lpuart1_rx_message[255];
extern uint8_t lpuart1_rx_message_index;
extern uint8_t lpuart1_rx_message_len;
extern uint8_t lpuart1_rx_done;

178
fw/Core/Inc/modbus.h Normal file
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@ -0,0 +1,178 @@
/*
* modbus.h
*
* Created on: Jul 18, 2021
* Author: user
*
* Modbus slave RTU library (does NOT support ASCII and TCP)
*
* Useful links:
* https://www.picotech.com/library/oscilloscopes/modbus-serial-protocol-decoding
* https://ipc2u.com/articles/knowledge-base/modbus-rtu-made-simple-with-detailed-descriptions-and-examples/
* https://modbus.org/docs/Modbus_over_serial_line_V1_02.pdf
* https://www.modbus.org/docs/Modbus_Application_Protocol_V1_1b.pdf
*
* Note that byte order is big endian.
*
* USAGE:
*
* 1) Implement functions modbus_callback_function() and modbus_uart_transmit_function()
* - modbus_uart_transmit_function() sends data via UART
* - modbus_callback_function() does the real work: read sensors, set outputs...
* note that when filling buffers (e.g. input_registers[]) user must
* ensure that all data is big-endian
* These functions are implementation-specific.
* 2) Set device address (variable modbus_device_address); you can do this either
* - setting modbus_device_address directly (modbus.h needs to be included, duh)
* - using modbus_set_device_address(uint8_t address) function
* Or you can leave address as-is (MODBUS_DEFAULT_SLAVE_ADDRESS) and set it via
* Modbus during runtime
* 3) Call modbus_process_msg() after message reception; you need to observe Modbus RTU timing:
* - pauses between chars in frame are less or equal to 1.5 char
* - pauses between frames are at least 3.5 chars (of silence)
* For more information see section 2.5.1.1 (MODBUS Message RTU Framing)
* in "MODBUS over Serial Line: Specification and Implementation Guide"
*
*/
#ifndef SRC_MODBUS_H_
#define SRC_MODBUS_H_
#include "stdint.h"
/*
* Defines & macros
*/
#define MODBUS_BROADCAST_ADDR 0
#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_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
/*
* Return values
*/
#define MODBUS_OK 0
#define MODBUS_ERROR -1 // generic error
#define MODBUS_ERROR_CRC -2 // checksum failed
#define MODBUS_ERROR_FRAME_INVALID -3 // invalid frame format / length
#define MODBUS_ERROR_OUT_OF_BOUNDS -4 // requested register is out of bounds
#define MODBUS_ERROR_FUNCTION_NOT_IMPLEMENTED -5 // function not implemented in callback
#define MODBUS_ERROR_REGISTER_NOT_IMPLEMENTED -6 // register not implemented in callback
/*
* Data types
*/
/* Public functions codes (Modbus Application protocol specification, section 5.1) */
typedef enum {
/* single bit access functions */
MODBUS_READ_COILS = 1,
MODBUS_READ_DO = 1, // alias
MODBUS_READ_DISCRETE_INPUTS = 2,
MODBUS_READ_DI = 2, // alias
MODBUS_WRITE_SINGLE_COIL = 5,
MODBUS_WRITE_SINGLE_DO = 5, // alias
MODBUS_WRITE_MULTIPLE_COILS = 15,
MODBUS_WRITE_MULTIPLE_DO = 15, // alias
/* 16-bit access functions */
MODBUS_READ_HOLDING_REGISTERS = 3,
MODBUS_READ_AO = 3, // alias
MODBUS_READ_INPUT_REGISTERS = 4,
MODBUS_READ_AI = 4, // alias
MODBUS_WRITE_SINGLE_REGISTER = 6,
MODBUS_WRITE_SINGLE_AO = 6, // alias
MODBUS_WRITE_MULTIPLE_REGISTERS = 16,
MODBUS_WRITE_MULTIPLE_AO = 16, // alias
MODBUS_MASK_WRITE_REGISTER = 22,
MODBUS_READ_WRITE_MULTIPLE_REGISTERS = 23,
MODBUS_READ_FIFO_QUEUE = 24,
/* file record access */
MODBUS_READ_FILE_RECORD = 20,
MODBUS_WRITE_FILE_RECORD = 21,
/* diagnostics */
MODBUS_READ_EXCEPTION_STATUS = 7,
MODBUS_DIAGNOSTIC = 8, /* sub codes: 00-18,20 */
MODBUS_GET_COM_EVENT_COUNTER = 11,
MODBUS_GET_COM_EVENT_LOG = 12,
MODBUS_REPORT_SLAVE_ID = 17,
MODBUS_READ_DEVICE_IDENTIFICATION = 43, /* sub codes: 14 */
} modbus_function_code_t;
typedef enum {
MODBUS_EXCEPTION_ILLEGAL_FUNCTION = 1,
MODBUS_EXCEPTION_ILLEGAL_DATA_ADDRESS = 2,
MODBUS_EXCEPTION_ILLEGAL_DATA_VALUE = 3,
MODBUS_EXCEPTION_SLAVE_DEVICE_FAILURE = 4,
MODBUS_EXCEPTION_ACKNOWLEDGE = 5,
MODBUS_EXCEPTION_SLAVE_DEVICE_BUSY = 6,
MODBUS_EXCEPTION_MEMORY_PARITY_ERROR = 8,
MODBUS_EXCEPTION_GATEWAY_PATH_UNAVAILABLE = 10,
MODBUS_EXCEPTION_GATEWAY_TARGET_DEVICE_FAILED_TO_RESPOND = 11,
} modbus_exception_code_t;
typedef struct {
uint8_t exception_code;
} exception_t;
typedef struct {
modbus_function_code_t function_code : 8;
uint16_t register_address; // e.g. first register of A0: 0
uint16_t register_number; // e.g. first register of A0: 40001
uint8_t register_count; // number of registers to be read/written
exception_t exception;
union {
uint8_t buffer8b[MODBUS_MAX_RTU_FRAME_SIZE];
uint16_t buffer16b[MODBUS_MAX_RTU_FRAME_SIZE/2];
uint16_t input_registers[MODBUS_MAX_REGISTERS];
uint16_t holding_registers[MODBUS_MAX_REGISTERS];
};
} modbus_transaction_t;
typedef enum {
MODBUS_DO_START_NUMBER = 1, // Discrete output coils
MODBUS_DO_END_NUMBER = 9999,
MODBUS_DI_START_NUMBER = 10001, // Discrete input contacts
MODBUS_DI_END_NUMBER = 19999,
MODBUS_AI_START_NUMBER = 30001, // Analog input registers
MODBUS_AI_END_NUMBER = 39999,
MODBUS_AO_START_NUMBER = 40001, // Analog output (holding registers)
MODBUS_AO_END_NUMBER = 49999
} modbus_register_number_t;
/*
* Global variables
*/
/* device address: declared in modbus.c */
extern uint8_t modbus_slave_address;
/* shared modbus buffer; defined in modbus.c; may be used elsewhere in code */
extern uint8_t modbus_buffer[];
/*
* Function prototypes
*/
/* process message: should be called in when modbus message was received (e.g. in main.c)
* modbus_process_msg() may call following functions:
* - modbus_callback_function() if data readout is requested
* - modbus_uart_transmit_function() if response is required
* Both functions have to be implemented by user.
*/
int8_t modbus_slave_process_msg(const uint8_t *buffer, int len);
int8_t modbus_slave_set_address(uint8_t address);
/* modbus callback function type - should be implemented by user (e.g. in main.c) */
int8_t modbus_slave_callback(modbus_transaction_t *transaction);
/* UART transmit function type - should be implemented by user (e.g. in main.c) */
int8_t modbus_transmit_function(uint8_t *buffer, int data_len);
#endif /* SRC_MODBUS_H_ */

24
fw/Core/Src/main.c
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@ -64,6 +64,16 @@ static void MX_TIM21_Init(void);
/* Private user code ---------------------------------------------------------*/
/* USER CODE BEGIN 0 */
int8_t modbus_slave_callback(modbus_transaction_t *transaction)
{
return MODBUS_ERROR_FUNCTION_NOT_IMPLEMENTED; /* nothing implemented yet! TODO */
}
int8_t modbus_transmit_function(uint8_t *buffer, int data_len)
{
return MODBUS_OK; /* TODO */
}
/* USER CODE END 0 */
@ -157,13 +167,13 @@ int main(void)
/* UART RX is done */
if (lpuart1_rx_done == 1)
{
/* Process the message */
uint8_t buff_pom[255];
for (uint8_t j = 0; j < lpuart1_rx_message_len; j ++)
{
buff_pom[j] = lpuart1_rx_message[j];
}
/* process_modbus_message(lpuart1_rx_message, lpuart1_rx_message_len); */
/* Process the message:
* message is stored in modbus_buffer[], no copying necessary;
* but we need to make sure that modbus_buffer[] will not be used while
* processing the message: this can be done by disabling RX interrupt */
LL_LPUART_DisableIT_RXNE(LPUART1);
modbus_slave_process_msg(modbus_buffer, lpuart1_rx_message_len);
LL_LPUART_EnableIT_RXNE(LPUART1);
/* Reset the RX DONE flag */
lpuart1_rx_done = 0;

223
fw/Core/Src/modbus.c Normal file
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@ -0,0 +1,223 @@
/*
* modbus.c
*
* Created on: Jul 18, 2021
* Author: user
*/
#include "modbus.h"
/*
* Global variables
*/
/* Modbus TX buffer; can be also used for RX in memory constrained systems (e.g. in main.c);
* NOTE if shared buffer is used for TX/RX, care must be taken to prevent writing into buffer
* during execution of modbus_process_message() */
uint8_t modbus_buffer[MODBUS_MAX_RTU_FRAME_SIZE];
/* device address: declared */
uint8_t modbus_slave_address = MODBUS_DEFAULT_SLAVE_ADDRESS;
/*
* CRC16 functions
* see https://modbus.org/docs/Modbus_over_serial_line_V1_02.pdf
* section 6.2.2
*/
/* CRC16 (without memory mapped values)
* taken from https://ctlsys.com/support/how_to_compute_the_modbus_rtu_message_crc/ */
uint16_t modbus_CRC16(const uint8_t *buf, int len)
{
uint16_t crc = 0xFFFF;
for (int pos = 0; pos < len; pos++) {
crc ^= (uint16_t)buf[pos]; // XOR byte into least sig. byte of crc
for (int i = 8; i != 0; i--) { // Loop over each bit
if ((crc & 0x0001) != 0) { // If the LSB is set
crc >>= 1; // Shift right and XOR 0xA001
crc ^= 0xA001;
} else { // Else LSB is not set
crc >>= 1; // Just shift right
}
}
}
// Note, this number has low and high bytes swapped, so use it accordingly (or swap bytes)
return crc;
}
/*
* Private functions
*/
/* 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 */
int8_t modbus_copy_reply_to_buffer(uint8_t *buffer, uint8_t *msg_len, modbus_transaction_t *transaction)
{
uint16_t crc16;
uint8_t byte_count;
buffer[0] = modbus_slave_address;
buffer[1] = transaction->function_code;
*msg_len = 5;
if (transaction->function_code | MODBUS_ERROR_FLAG) {
/* sending error reply */
buffer[2] = transaction->exception.exception_code;
}
switch (transaction->function_code) {
case MODBUS_READ_HOLDING_REGISTERS:
case MODBUS_READ_INPUT_REGISTERS:
byte_count = transaction->register_count * 2;
buffer[2] = 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;
}
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;
}
/*
* Public function definitions
*/
int8_t modbus_slave_set_address(uint8_t address)
{
if (address == 0) {
/* address 0 is broadcast address */
return MODBUS_ERROR;
}
modbus_slave_address = address;
return MODBUS_OK;
}
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;
if (len < MODBUS_MINIMAL_FRAME_LEN) {
/* frame too short; return error */
return MODBUS_ERROR_FRAME_INVALID;
}
/* check CRC first */
uint16_t crc_received = (buffer[len - 1] << 8) | buffer[len - 2];
uint16_t crc_calculated = modbus_CRC16(buffer, len - 2);
if (crc_received != crc_calculated) {
/* CRC mismatch, return error */
//printf("crc mismatch: received 0x%x, calculated 0x%x\n", crc_received, crc_calculated);
return MODBUS_ERROR_CRC;
}
/* check if address matches ours */
uint8_t address = buffer[buffer_pos++];
if (address != modbus_slave_address && address != MODBUS_BROADCAST_ADDR) {
/* Message is not for us */
return MODBUS_OK;
}
/* get function code */
transaction.function_code = buffer[buffer_pos++];
transaction.exception.exception_code = 0;
if (transaction.function_code == MODBUS_READ_DEVICE_IDENTIFICATION) {
// TODO
goto modbus_send;
}
/* set starting register number */
switch (transaction.function_code) {
/* coils */
case MODBUS_READ_DO:
case MODBUS_WRITE_SINGLE_DO:
case MODBUS_WRITE_MULTIPLE_DO:
transaction.register_number = MODBUS_DO_START_NUMBER;
break;
/* discrete inputs */
case MODBUS_READ_DI:
transaction.register_number = MODBUS_DI_START_NUMBER;
break;
/* input registers */
case MODBUS_READ_AI:
transaction.register_number = MODBUS_AI_START_NUMBER;
break;
/* holding registers */
case MODBUS_READ_AO:
case MODBUS_WRITE_SINGLE_AO:
case MODBUS_WRITE_MULTIPLE_AO:
case MODBUS_READ_WRITE_MULTIPLE_REGISTERS:
transaction.register_number = MODBUS_AO_START_NUMBER;
break;
}
#define MODBUS_FLAG_WRITE 0x01
#define MODBUS_FLAG_SINGLE 0x02
uint8_t flags = 0x00;
/* process message */
switch (transaction.function_code) {
case MODBUS_WRITE_SINGLE_COIL:
case MODBUS_WRITE_SINGLE_REGISTER: /* holding register */
flags |= MODBUS_FLAG_SINGLE;
case MODBUS_WRITE_MULTIPLE_COILS:
case MODBUS_WRITE_MULTIPLE_REGISTERS:
flags |= MODBUS_FLAG_WRITE;
case MODBUS_READ_DISCRETE_INPUTS:
case MODBUS_READ_COILS:
case MODBUS_READ_INPUT_REGISTERS:
case MODBUS_READ_HOLDING_REGISTERS:
if (len < (MODBUS_MINIMAL_FRAME_LEN + 4)) {
/* buffer too short to contain everything we need */
return MODBUS_ERROR;
}
transaction.register_address = (buffer[buffer_pos++] << 8) | buffer[buffer_pos++];
transaction.register_count = (buffer[buffer_pos++] << 8) | buffer[buffer_pos++];
if (
transaction.register_count < 1 ||
transaction.register_count > MODBUS_MAX_REGISTERS
) {
transaction.exception.exception_code = MODBUS_EXCEPTION_ILLEGAL_DATA_VALUE;
}
// add offset to register number
transaction.register_number += transaction.register_address;
break;
default:
/* function code not known / not implemented, reply with
* ExceptionCode 1 */
transaction.exception.exception_code = MODBUS_EXCEPTION_ILLEGAL_FUNCTION;
break;
}
/* data in modbus_buffer have been processed and buffer can be re-used for TX */
/* handle reply */
if (transaction.exception.exception_code != 0) {
/* indicate error */
transaction.function_code |= MODBUS_ERROR_FLAG;
} else {
callback_result = modbus_slave_callback(&transaction);
/* error handling */
if (callback_result != MODBUS_OK) {
transaction.function_code |= MODBUS_ERROR_FLAG;
if (callback_result == MODBUS_ERROR_FUNCTION_NOT_IMPLEMENTED) {
transaction.exception.exception_code = MODBUS_EXCEPTION_ILLEGAL_FUNCTION;
} else if (callback_result == MODBUS_ERROR_REGISTER_NOT_IMPLEMENTED) {
transaction.exception.exception_code = MODBUS_EXCEPTION_ILLEGAL_DATA_ADDRESS;
}
}
}
uint8_t msg_len = 0;
modbus_send:
if (address != MODBUS_BROADCAST_ADDR) {
/* send only if master request was not broadcast */
modbus_copy_reply_to_buffer(modbus_buffer, &msg_len, &transaction);
modbus_transmit_function(modbus_buffer, msg_len);
}
}

7
fw/Core/Src/stm32l0xx_it.c
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@ -42,7 +42,6 @@
/* Private variables ---------------------------------------------------------*/
/* USER CODE BEGIN PV */
uint8_t lpuart1_rx_message[255];
uint8_t lpuart1_rx_message_index = 0;
uint8_t lpuart1_rx_message_len = 0;
uint8_t lpuart1_rx_done = 0;
@ -196,8 +195,10 @@ void LPUART1_IRQHandler(void)
void LPUART1_CharReception_Callback( void )
{
uint16_t lpuart1_rx_bit = LL_LPUART_ReceiveData9(LPUART1);
lpuart1_rx_message[lpuart1_rx_message_index] = (uint8_t)lpuart1_rx_bit;
lpuart1_rx_message_index++;
if (lpuart1_rx_message_index < (MODBUS_BUFFER_SIZE - 1)) {
/* buffer (defined in modbus.c) is shared for TX and RX */
modbus_buffer[lpuart1_rx_message_index++] = (uint8_t)lpuart1_rx_bit;
}
}
/* USER CODE END 1 */
/************************ (C) COPYRIGHT STMicroelectronics *****END OF FILE****/