// =================================================================================================

// eModbus: Copyright 2020 by Michael Harwerth, Bert Melis and the contributors to eModbus

// MIT license - see license.md for details

// =================================================================================================

#include "options.h"

#if HAS_FREERTOS || HAS_RP2040_FREERTOS

#include "ModbusMessage.h"

#include "RTUutils.h"

#undef LOCAL_LOG_LEVEL

// #define LOCAL_LOG_LEVEL LOG_LEVEL_VERBOSE

#include "Logging.h"

// CRC16 pre-calculated tables

static constexpr uint8_t crcHiTable[] = {

0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81,

0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0,

0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01,

0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,

0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81,

0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0,

0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01,

0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,

0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81,

0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0,

0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01,

0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,

0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81,

0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0,

0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01,

0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,

0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81,

0x40

};

static constexpr uint8_t crcLoTable[] = {

0x00, 0xC0, 0xC1, 0x01, 0xC3, 0x03, 0x02, 0xC2, 0xC6, 0x06, 0x07, 0xC7, 0x05, 0xC5, 0xC4,

0x04, 0xCC, 0x0C, 0x0D, 0xCD, 0x0F, 0xCF, 0xCE, 0x0E, 0x0A, 0xCA, 0xCB, 0x0B, 0xC9, 0x09,

0x08, 0xC8, 0xD8, 0x18, 0x19, 0xD9, 0x1B, 0xDB, 0xDA, 0x1A, 0x1E, 0xDE, 0xDF, 0x1F, 0xDD,

0x1D, 0x1C, 0xDC, 0x14, 0xD4, 0xD5, 0x15, 0xD7, 0x17, 0x16, 0xD6, 0xD2, 0x12, 0x13, 0xD3,

0x11, 0xD1, 0xD0, 0x10, 0xF0, 0x30, 0x31, 0xF1, 0x33, 0xF3, 0xF2, 0x32, 0x36, 0xF6, 0xF7,

0x37, 0xF5, 0x35, 0x34, 0xF4, 0x3C, 0xFC, 0xFD, 0x3D, 0xFF, 0x3F, 0x3E, 0xFE, 0xFA, 0x3A,

0x3B, 0xFB, 0x39, 0xF9, 0xF8, 0x38, 0x28, 0xE8, 0xE9, 0x29, 0xEB, 0x2B, 0x2A, 0xEA, 0xEE,

0x2E, 0x2F, 0xEF, 0x2D, 0xED, 0xEC, 0x2C, 0xE4, 0x24, 0x25, 0xE5, 0x27, 0xE7, 0xE6, 0x26,

0x22, 0xE2, 0xE3, 0x23, 0xE1, 0x21, 0x20, 0xE0, 0xA0, 0x60, 0x61, 0xA1, 0x63, 0xA3, 0xA2,

0x62, 0x66, 0xA6, 0xA7, 0x67, 0xA5, 0x65, 0x64, 0xA4, 0x6C, 0xAC, 0xAD, 0x6D, 0xAF, 0x6F,

0x6E, 0xAE, 0xAA, 0x6A, 0x6B, 0xAB, 0x69, 0xA9, 0xA8, 0x68, 0x78, 0xB8, 0xB9, 0x79, 0xBB,

0x7B, 0x7A, 0xBA, 0xBE, 0x7E, 0x7F, 0xBF, 0x7D, 0xBD, 0xBC, 0x7C, 0xB4, 0x74, 0x75, 0xB5,

0x77, 0xB7, 0xB6, 0x76, 0x72, 0xB2, 0xB3, 0x73, 0xB1, 0x71, 0x70, 0xB0, 0x50, 0x90, 0x91,

0x51, 0x93, 0x53, 0x52, 0x92, 0x96, 0x56, 0x57, 0x97, 0x55, 0x95, 0x94, 0x54, 0x9C, 0x5C,

0x5D, 0x9D, 0x5F, 0x9F, 0x9E, 0x5E, 0x5A, 0x9A, 0x9B, 0x5B, 0x99, 0x59, 0x58, 0x98, 0x88,

0x48, 0x49, 0x89, 0x4B, 0x8B, 0x8A, 0x4A, 0x4E, 0x8E, 0x8F, 0x4F, 0x8D, 0x4D, 0x4C, 0x8C,

0x44, 0x84, 0x85, 0x45, 0x87, 0x47, 0x46, 0x86, 0x82, 0x42, 0x43, 0x83, 0x41, 0x81, 0x80,

0x40

};

// calcCRC: calculate Modbus CRC16 on a given array of bytes

uint16_t RTUutils::calcCRC(const uint8_t *data, uint16_t len) {

uint8_t crcHi = 0xFF;

uint8_t crcLo = 0xFF;

while (len--) {

uint8_t index = crcLo ^ *data++;

crcLo = crcHi ^ crcHiTable[index];

crcHi = crcLoTable[index];

}

return (crcHi << 8 | crcLo);

}

// calcCRC: calculate Modbus CRC16 on a given message

uint16_t RTUutils::calcCRC(ModbusMessage msg) {

return calcCRC(msg.data(), msg.size());

}

// validCRC #1: check the given CRC in a block of data for correctness

bool RTUutils::validCRC(const uint8_t *data, uint16_t len) {

return validCRC(data, len - 2, data[len - 2] | (data[len - 1] << 8));

}

// validCRC #2: check the CRC of a block of data against a given one for equality

bool RTUutils::validCRC(const uint8_t *data, uint16_t len, uint16_t CRC) {

uint16_t crc16 = calcCRC(data, len);

if (CRC == crc16) return true;

return false;

}

// validCRC #3: check the given CRC in a message for correctness

bool RTUutils::validCRC(ModbusMessage msg) {

return validCRC(msg.data(), msg.size() - 2, msg[msg.size() - 2] | (msg[msg.size() - 1] << 8));

}

// validCRC #4: check the CRC of a message against a given one for equality

bool RTUutils::validCRC(ModbusMessage msg, uint16_t CRC) {

return validCRC(msg.data(), msg.size(), CRC);

}

// addCRC: calculate the CRC for a given RTUMessage and add it to the end

void RTUutils::addCRC(ModbusMessage& raw) {

uint16_t crc16 = calcCRC(raw.data(), raw.size());

raw.push_back(crc16 & 0xff);

raw.push_back((crc16 >> 8) & 0xFF);

}

// calculateInterval: determine the minimal gap time between messages

uint32_t RTUutils::calculateInterval(uint32_t baudRate) {

uint32_t interval = 0;

// silent interval is at least 3.5x character time

interval = 35000000UL / baudRate; // 3.5 * 10 bits * 1000 µs * 1000 ms / baud

if (interval < 1750) interval = 1750; // lower limit according to Modbus RTU standard

LOG_V("Calc interval(%u)=%u\n", baudRate, interval);

return interval;

}

// send: send a message via Serial, watching interval times - including CRC!

void RTUutils::send(Stream& serial, unsigned long& lastMicros, uint32_t interval, RTScallback rts, const uint8_t *data, uint16_t len, bool ASCIImode) {

// Clear serial buffers

while (serial.available()) serial.read();

// Treat ASCII differently

if (ASCIImode) {

// Toggle rtsPin, if necessary

rts(HIGH);

// Yes, ASCII mode. Send lead-in

serial.write(':');

uint16_t cnt = len;

uint8_t crc = 0;

uint8_t *cp = (uint8_t *)data;

// Loop over all bytes of the message

while (cnt--) {

// Write two nibbles as ASCII characters

serial.write(ASCIIwrite[(*cp >> 4) & 0x0F]);

serial.write(ASCIIwrite[*cp & 0x0F]);

// Advance CRC

crc += *cp;

// Next byte

cp++;

}

// Finalize CRC (2's complement)

crc = ~crc;

crc++;

// Write ist - two nibbles as ASCII characters

serial.write(ASCIIwrite[(crc >> 4) & 0x0F]);

serial.write(ASCIIwrite[crc & 0x0F]);

// Send lead-out

serial.write("\r\n");

serial.flush();

// Toggle rtsPin, if necessary

rts(LOW);

} else {

// RTU mode

uint16_t crc16 = calcCRC(data, len);

// Respect interval - we must not toggle rtsPin before

if (micros() - lastMicros < interval) delayMicroseconds(interval - (micros() - lastMicros));

// Toggle rtsPin, if necessary

rts(HIGH);

// Write message

serial.write(data, len);

// Write CRC in LSB order

serial.write(crc16 & 0xff);

serial.write((crc16 >> 8) & 0xFF);

serial.flush();

// Toggle rtsPin, if necessary

rts(LOW);

}

HEXDUMP_D("Sent packet", data, len);

// Mark end-of-message time for next interval

lastMicros = micros();

}

// send: send a message via Serial, watching interval times - including CRC!

void RTUutils::send(Stream& serial, unsigned long& lastMicros, uint32_t interval, RTScallback rts, ModbusMessage raw, bool ASCIImode) {

send(serial, lastMicros, interval, rts, raw.data(), raw.size(), ASCIImode);

}

// receive: get (any) message from Serial, taking care of timeout and interval

ModbusMessage RTUutils::receive(uint8_t caller, Stream& serial, uint32_t timeout, unsigned long& lastMicros, uint32_t interval, bool ASCIImode, bool skipLeadingZeroBytes) {

// Allocate initial receive buffer size: 1 block of BUFBLOCKSIZE bytes

const uint16_t BUFBLOCKSIZE(512);

uint8_t *buffer = new uint8_t[BUFBLOCKSIZE];

ModbusMessage rv;

// Index into buffer

uint16_t bufferPtr = 0;

// Byte read

int b = 0;

// State machine states, RTU mode

enum STATES : uint8_t { WAIT_DATA = 0, IN_PACKET, DATA_READ, FINISHED };

// State machine states, ASCII mode

enum ASTATES : uint8_t { A_WAIT_DATA = 0, A_DATA, A_WAIT_LEAD_OUT, A_FINISHED };

uint8_t state;

// Timeout tracker

unsigned long TimeOut = millis();

// RTU mode?

if (!ASCIImode) {

// Yes.

state = WAIT_DATA;

// interval tracker

lastMicros = micros();

while (state != FINISHED) {

switch (state) {

// WAIT_DATA: await first data byte, but watch timeout

case WAIT_DATA:

// Blindly try to read a byte

b = serial.read();

// Did we get one?

if (b >= 0) {

// Yes. Note the time.

lastMicros = micros();

// Do we need to skip it, if it is zero?

if (b > 0 || !skipLeadingZeroBytes) {

// No, we can go process it regularly

buffer[bufferPtr++] = b;

state = IN_PACKET;

}

} else {

// No, we had no byte. Just check the timeout period

if (millis() - TimeOut >= timeout) {

rv.push_back(TIMEOUT);

state = FINISHED;

}

delay(1);

}

break;

// IN_PACKET: read data until a gap of at least _interval time passed without another byte arriving

case IN_PACKET:

// tight loop until finished reading or error

while (state == IN_PACKET) {

// Is there a byte?

while (serial.available()) {

// Yes, collect it

buffer[bufferPtr++] = serial.read();

// Mark time of last byte

lastMicros = micros();

// Buffer full?

if (bufferPtr >= BUFBLOCKSIZE) {

// Yes. Something fishy here - bail out!

rv.push_back(PACKET_LENGTH_ERROR);

state = FINISHED;

break;

}

}

// No more byte read

if (state == IN_PACKET) {

// Are we past the interval gap?

if (micros() - lastMicros >= interval) {

// Yes, terminate reading

LOG_V("%c/%ldus without data after %u\n", (const char)caller, micros() - lastMicros, bufferPtr);

state = DATA_READ;

break;

} else {

// Give some slack

delay(1);

}

}

}

break;

// DATA_READ: successfully gathered some data. Prepare return object.

case DATA_READ:

// Did we get a sensible buffer length?

LOG_V("%c/", (const char)caller);

HEXDUMP_V("Raw buffer received", buffer, bufferPtr);

if (bufferPtr >= 4)

{

// Yes. Check CRC

if (!validCRC(buffer, bufferPtr)) {

// Ooops. CRC is wrong.

rv.push_back(CRC_ERROR);

} else {

// CRC was fine, Now allocate response object without the CRC

for (uint16_t i = 0; i < bufferPtr - 2; ++i) {

rv.push_back(buffer[i]);

}

}

} else {

// No, packet was too short for anything usable. Return error

rv.push_back(PACKET_LENGTH_ERROR);

}

state = FINISHED;

break;

// FINISHED: we are done, clean up.

case FINISHED:

// CLear serial buffer in case something is left trailing

// May happen with servers too slow!

while (serial.available()) serial.read();

break;

}

}

} else {

// We are in ASCII mode.

state = A_WAIT_DATA;

// Track nibbles in a byte

bool byteComplete = true;

// Track bytes read

bool hadBytes = false;

// ASCII crc byte

uint8_t crc = 0;

while (state != A_FINISHED) {

// Always watch timeout - 1s

if (millis() - TimeOut >= timeout) {

// Timeout! Bail out with error

rv.push_back(TIMEOUT);

state = A_FINISHED;

} else {

// Still in time. Check for another byte on serial

if (!hadBytes && serial.available()) {

b = serial.read();

if (b >= 0) {

hadBytes = true;

}

}

// Only use state machine with new data arrived

if (hadBytes) {

// First reset timeout

TimeOut = millis();

// Is it a valid character?

if ((b & 0x80) || ASCIIread[b] == 0xFF) {

// No. Report error and leave.

rv.clear();

rv.push_back(ASCII_INVALID_CHAR);

hadBytes = false;

state = A_FINISHED;

} else {

// Yes, is valid. Furtheron use interpreted byte

b = ASCIIread[b];

switch (state) {

// A_WAIT_DATA: await lead-in byte ':'

case A_WAIT_DATA:

// Is it the lead-in?

if (b == 0xF0) {

// Yes, proceed to data read state

state = A_DATA;

}

// byte was consumed in any case

hadBytes = false;

break;

// A_DATA: read data as it comes

case A_DATA:

// Lead-out byte 1 received?

if (b == 0xF1) {

// Yes. Was last buffer byte completed?

if (byteComplete) {

// Yes. Move to final state

state = A_WAIT_LEAD_OUT;

} else {

// No, signal with error

rv.push_back(PACKET_LENGTH_ERROR);

state = A_FINISHED;

}

} else {

// No lead-out, must be data byte.

// Is it valid?

if (b < 0xF0) {

// Yes. Add it into current buffer byte

buffer[bufferPtr] <<= 4;

buffer[bufferPtr] += (b & 0x0F);

// Advance nibble

byteComplete = !byteComplete;

// Was it the second of the byte?

if (byteComplete) {

// Yes. Advance CRC and move buffer pointer by one

crc += buffer[bufferPtr];

bufferPtr++;

buffer[bufferPtr] = 0;

}

} else {

// No, garbage. report error

rv.push_back(ASCII_INVALID_CHAR);

state = A_FINISHED;

}

}

hadBytes = false;

break;

// A_WAIT_LEAD_OUT: await \n

case A_WAIT_LEAD_OUT:

if (b == 0xF2) {

// Lead-out byte 2 received. Transfer buffer to returned message

LOG_V("%c/", (const char)caller);

HEXDUMP_V("Raw buffer received", buffer, bufferPtr);

// Did we get a sensible buffer length?

if (bufferPtr >= 3)

{

// Yes. Was the CRC calculated correctly?

if (crc == 0) {

// Yes, reduce buffer by 1 to get rid of CRC byte...

bufferPtr--;

// Move data into returned message

for (uint16_t i = 0; i < bufferPtr; ++i) {

rv.push_back(buffer[i]);

}

} else {

// No, CRC calculation seems to have failed

rv.push_back(ASCII_CRC_ERR);

}

} else {

// No, packet was too short for anything usable. Return error

rv.push_back(PACKET_LENGTH_ERROR);

}

} else {

// No lead out byte 2, but something else - report error.

rv.push_back(ASCII_FRAME_ERR);

}

state = A_FINISHED;

break;

// A_FINISHED: Message completed

case A_FINISHED:

// Clean up serial buffer

while (serial.available()) serial.read();

break;

}

}

} else {

// No data received, so give the task scheduler room to breathe

delay(1);

}

}

}

}

// Deallocate buffer

delete[] buffer;

LOG_D("%c/", (const char)caller);

HEXDUMP_D("Received packet", rv.data(), rv.size());

return rv;

}

// Lower 7 bit ASCII characters - all invalid are set to 0xFF

const uint8_t RTUutils::ASCIIread[] = {

/* 00-07 */ 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,

/* 08-0F */ 0xFF, 0xFF, 0xF2, 0xFF, 0xFF, 0xF1, 0xFF, 0xFF, // LF + CR

/* 10-17 */ 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,

/* 18-1F */ 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,

/* 20-27 */ 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,

/* 28-2F */ 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,

/* 30-37 */ 0, 1, 2, 3, 4, 5, 6, 7, // digits 0-7

/* 38-3F */ 8, 9, 0xF0, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // digits 8 + 9, :

/* 40-47 */ 0xFF, 10, 11, 12, 13, 14, 15, 0xFF, // digits A-F

/* 48-4F */ 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,

/* 50-57 */ 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,

/* 58-5F */ 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,

/* 60-67 */ 0xFF, 10, 11, 12, 13, 14, 15, 0xFF, // digits a-f

/* 68-6F */ 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,

/* 70-77 */ 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,

/* 78-7F */ 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF

};

// Writable ASCII chars for hex digits

const uint8_t RTUutils::ASCIIwrite[] = { 0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37,

0x38, 0x39, 0x41, 0x42, 0x43, 0x44, 0x45, 0x46

};

#endif