proposal for I2C master/slave example #5360
There are no files selected for viewing
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,209 @@ | ||
| //------------------------------------------------------------------------------------- | ||
| // CRC16 support class | ||
| // Based on various examples found on the web | ||
| // Copyright (C) 2014 Vincenzo Mennella (see license.txt) | ||
| // History | ||
| // 0.1.0 31/05/2014: First public code release | ||
| // 0.1.1 17/12/2014: Minor revision and commented code | ||
| // | ||
| // License | ||
| // "MIT Open Source Software License": | ||
| // Permission is hereby granted, free of charge, to any person obtaining a copy of | ||
| // this software and associated documentation files (the "Software"), to deal in the | ||
| // Software without restriction, including without limitation the rights to use, copy, | ||
| // modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, | ||
| // and to permit persons to whom the Software is furnished to do so, subject to | ||
| // the following conditions: | ||
| // | ||
| // The above copyright notice and this permission notice shall be included in all | ||
| // copies or substantial portions of the Software. | ||
| // | ||
| // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR | ||
| // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS | ||
| // FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR | ||
| // COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER | ||
| // IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION | ||
| // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. | ||
| //------------------------------------------------------------------------------------- | ||
| #ifndef CRC16_H | ||
| #define CRC16_H | ||
| #define LIBRARY_VERSION_CRC16_H "0.1.1" | ||
|
|
||
| #if defined(ARDUINO) && ARDUINO >= 100 | ||
| #include "Arduino.h" | ||
| #elif defined(ARDUINO) | ||
| #include "WProgram.h" | ||
| #else | ||
| #include <cstdint> | ||
| #endif | ||
|
|
||
| class Crc16 { | ||
| private: | ||
| //Crc parameters | ||
| uint16_t _msbMask; | ||
| uint16_t _mask; | ||
| uint16_t _xorIn; | ||
| uint16_t _xorOut; | ||
| uint16_t _polynomial; | ||
| uint8_t _reflectIn; | ||
|
There was a problem hiding this comment. I guess these are uint8_t instead of bool for size? It's ok to do that, but at the very least the interface args should be bool type. |
||
| uint8_t _reflectOut; | ||
| //Crc value | ||
| uint16_t _crc; | ||
| uint8_t reflect(uint8_t data, uint8_t bits = 32); | ||
|
|
||
| public: | ||
| inline Crc16() | ||
| { | ||
| //Default to XModem parameters | ||
| _reflectIn = false; | ||
| _reflectOut = false; | ||
| _polynomial = 0x1021; | ||
| _xorIn = 0x0000; | ||
| _xorOut = 0x0000; | ||
| _msbMask = 0x8000; | ||
| _mask = 0xFFFF; | ||
| _crc = _xorIn; | ||
| } | ||
| inline Crc16(uint8_t reflectIn, uint8_t reflectOut, uint16_t polynomial, uint16_t xorIn, uint16_t xorOut, uint16_t msbMask, uint16_t mask) | ||
|
There was a problem hiding this comment. I suggest the args reflectIn/Out be bool type |
||
| { | ||
| _reflectIn = reflectIn; | ||
| _reflectOut = reflectOut; | ||
| _polynomial = polynomial; | ||
| _xorIn = xorIn; | ||
| _xorOut = xorOut; | ||
| _msbMask = msbMask; | ||
| _mask = mask; | ||
| _crc = _xorIn; | ||
| } | ||
| inline void clearCrc(); | ||
| inline void updateCrc(uint8_t data); | ||
| inline uint16_t getCrc(); | ||
| inline unsigned int fastCrc(uint8_t data[], uint8_t start, uint16_t length, uint8_t reflectIn, uint8_t reflectOut, uint16_t polynomial, uint16_t xorIn, uint16_t xorOut, uint16_t msbMask, uint16_t mask); | ||
|
|
||
| inline unsigned int XModemCrc(uint8_t data[], uint8_t start, uint16_t length) | ||
|
There was a problem hiding this comment. I suggest changing the signature to: This assures that the dataSize value always corresponds to the size of the array passed in as an arg. However, this works only for arrays of predetermined size, and not for dynamically allocated arrays. In this last case, the function signature to use should be: Of course, both can coexist as overloads. |
||
| { | ||
| // XModem parameters: poly=0x1021 init=0x0000 refin=false refout=false xorout=0x0000 | ||
| return fastCrc(data, start, length, false, false, 0x1021, 0x0000, 0x0000, 0x8000, 0xffff); | ||
| } | ||
| }; | ||
|
|
||
| //--------------------------------------------------- | ||
| // Initialize crc calculation | ||
| //--------------------------------------------------- | ||
| void Crc16::clearCrc() | ||
| { | ||
| _crc = _xorIn; | ||
| } | ||
| //--------------------------------------------------- | ||
| // Update crc with new data | ||
| //--------------------------------------------------- | ||
| void Crc16::updateCrc(uint8_t data) | ||
| { | ||
| if (_reflectIn != 0) | ||
| data = (uint8_t) reflect(data, 8); | ||
|
|
||
| int j = 0x80; | ||
|
|
||
| while (j > 0) | ||
| { | ||
| uint16_t bit = (uint16_t)(_crc & _msbMask); | ||
|
|
||
| _crc <<= 1; | ||
|
|
||
| if ((data & j) != 0) | ||
| { | ||
| bit = (uint16_t)(bit ^ _msbMask); | ||
| } | ||
|
|
||
| if (bit != 0) | ||
| { | ||
| _crc ^= _polynomial; | ||
| } | ||
|
|
||
| j >>= 1; | ||
| } | ||
| } | ||
|
|
||
| //--------------------------------------------------- | ||
| // Get final crc value | ||
| //--------------------------------------------------- | ||
| uint16_t Crc16::getCrc() | ||
| { | ||
| if (_reflectOut != 0) | ||
| _crc = (unsigned int)((reflect(_crc) ^ _xorOut) & _mask); | ||
|
|
||
| return _crc; | ||
| } | ||
|
|
||
| //--------------------------------------------------- | ||
| // Calculate generic crc code on data array | ||
| // Examples of crc 16: | ||
| // Kermit: width=16 poly=0x1021 init=0x0000 refin=true refout=true xorout=0x0000 check=0x2189 | ||
| // Modbus: width=16 poly=0x8005 init=0xffff refin=true refout=true xorout=0x0000 check=0x4b37 | ||
| // XModem: width=16 poly=0x1021 init=0x0000 refin=false refout=false xorout=0x0000 check=0x31c3 | ||
| // CCITT-False: width=16 poly=0x1021 init=0xffff refin=false refout=false xorout=0x0000 check=0x29b1 | ||
| //--------------------------------------------------- | ||
| unsigned int Crc16::fastCrc(uint8_t data[], uint8_t start, uint16_t length, uint8_t reflectIn, uint8_t reflectOut, uint16_t polynomial, uint16_t xorIn, uint16_t xorOut, uint16_t msbMask, uint16_t mask) | ||
| { | ||
| unsigned int crc = xorIn; | ||
|
|
||
| int j; | ||
| uint8_t c; | ||
| unsigned int bit; | ||
|
|
||
| if (length == 0) return crc; | ||
|
|
||
| for (int i = start; i < (start + length); i++) | ||
| { | ||
| c = data[i]; | ||
|
|
||
| if (reflectIn != 0) | ||
| c = (uint8_t) reflect(c, 8); | ||
|
|
||
| j = 0x80; | ||
|
|
||
| while (j > 0) | ||
| { | ||
| bit = (unsigned int)(crc & msbMask); | ||
| crc <<= 1; | ||
|
|
||
| if ((c & j) != 0) | ||
| { | ||
| bit = (unsigned int)(bit ^ msbMask); | ||
| } | ||
|
|
||
| if (bit != 0) | ||
| { | ||
| crc ^= polynomial; | ||
| } | ||
|
|
||
| j >>= 1; | ||
| } | ||
| } | ||
|
|
||
| if (reflectOut != 0) | ||
| crc = (unsigned int)((reflect(crc) ^ xorOut) & mask); | ||
|
|
||
| return crc; | ||
| } | ||
|
|
||
| //------------------------------------------------------- | ||
| // Reflects bit in a uint8_t | ||
| //------------------------------------------------------- | ||
| uint8_t Crc16::reflect(uint8_t data, uint8_t bits) | ||
| { | ||
| unsigned long reflection = 0x00000000; | ||
| // Reflect the data about the center bit. | ||
| for (uint8_t bit = 0; bit < bits; bit++) | ||
| { | ||
| // If the LSB bit is set, set the reflection of it. | ||
| if ((data & 0x01) != 0) | ||
| { | ||
| reflection |= (unsigned long)(1 << ((bits - 1) - bit)); | ||
| } | ||
|
|
||
| data = (uint8_t)(data >> 1); | ||
| } | ||
|
|
||
| return reflection; | ||
| } | ||
| #endif | ||
Oops, something went wrong.
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
There was a problem hiding this comment.
Choose a reason for hiding this comment
The reason will be displayed to describe this comment to others. Learn more.
I know this is not your code, but I thought to add some suggestions anyways. It's ok to ignore them 😛
Globally, consider adding const-ness to all relevant args.