#ESP32, #CRC, #CRC-8, #CRC-16, #CRC-32, #CRC-64, #SML, #CRC-12, #CRC-7, #C, #PYTHON, #JAVASCRIPT
provides functions to calculate a crc (1-64bit)
The initial motivation behind creating a CRC library was to have a universal function (written in the C programming language) that is both fast and capable of calculating any CRC for microcontrollers. However the calculation of the lookup table for fast CRC computation can be expensive in terms of time and memory usage. (e.g., 8bit lookup values are stored in 64bit unsigend integers unless you didn't reconfigure the code). The next logical step is to precalculate the lookup table and incorporate it then (manually) into the code. To solve the memory issue as well, the CRC function is co-generated during the creation of the lookup table. It’s not mind-blowing, but it’s a journey.
javascript calculates lookup table only and create C codes.
C, Python
To calculate a CRC you need to have an initialized CRC handle (CRChandle_t). The handle can be initialized statically (see example 2) or dynamically. How to create the code
please refer to example 3. Static initialization will save the time of calculating the CRC table which may take at least 3900 calculations which may important to
your application. To create a CRC handle from a polynom, pass it along with the CRC options to the CRCCreate. If the CRC handle is not longer used,
the handle can be freed by DestroyCRC, if the handle was not allocated statically.
- a. initialize CRC by providig necessary details:
CRChandle_t *CRCCreate(uint8_t CRCbits, CRC_t Polynom, CRC_t Init, bool RefIn, bool RefOut, CRC_t XOrOut)
CRCbits: Number of bits for CRC value. Supported values are 1 to 64.
Polynom: CRC polynom
Init: CRC initial value
RefIn: reflect bit order of input stream (true/ false)
RefOut: reflect CRC value (true/ false)
XOrOut: Xor CRC value after processing the input
Function will fail, if number of crcbits are not supported or system does not provided enough memory to hold the CRChandle_t
- b. initialize CRC by specifing a name (see source code for valid names ;-) ):
CRChandle_t *CRCCreateFromName(const char *CRCname)
CRCname: name of CRC
Function will fail, if number of crcbits are not supported, name is not known or system does not provided enough memory to hold the CRChandle_t
-
Calculate CRC:
CRC_t CRC(const CRChandle_t *CRChandle, const uint8_t *Buffer, size_t Length)
CRChandle: handle of CRC
Buffer: data
Length: length of data -
a. Dump CRC lookup table as C code to initialize a static CRC handle while compiling:
char *CRCCreateCCode(CRChandle_t *CRChandle)
CRChandle: handle of CRC
Function will allocate memory for the generated source code.
- a. Dump CRC functioan code including the lookup table as C code:
char *CRCCreateCCode2(const CRChandle_t *CRChandle)
CRChandle: handle of CRC
Function will allocate memory for the generated source code.
- Destroy a non static CRC handle
void CRCDestroy(CRChandle_t *CRChandle)
CRChandle: handle of CRC
CRC are initialized by calling the class methods CRCCreate or CRCCreateFromName. When using the first option, provide the neccessary
details when calling the function. With CRCCreateFromName you need to pass along the name of a CRC. Unfortunatelly no naming standard
exists.
- a. initialize CRC_c by providig necessary details:
CRC_c CRCCreate(CRCbits, Polynom, Init, bool RefIn, bool RefOut, XOrOut)
CRCbits: Number of bits for CRC value. Supported values are 1 to 64.
Polynom: CRC polynom
Init: CRC initial value
RefIn: reflect bit order of input stream (true/ false)
RefOut: reflect CRC value (true/ false)
XOrOut: Xor CRC value after processing the input
Function will fail, if number of crcbits are bigger than 64.
- b. initialize CRC_c by specifing a name (see source code for valid names ;-) ):
CRCCreateFromName(CRCname)
CRCname: name of CRC
Function will fail if name is unknown
-
Calculate CRC:
CRC(Buffer)
Buffer: data (bytes) -
Dump CRC_c as Python code to get a "static" CRC_c:
CRCCreatePythonCode()
Code allows only to initialize the CRC_c class and dump C code CRCCreateCCode2 for CRC calculation. See the application folder for an example how to use.
#include "CRC.h"
static CRChandle_t *CRC_CCITT16 = NULL;
...
// create CRC table for smart message protocol (SML) once:
// 16bits
// polynom is x^{16} + x^{12} + x^5 + 1
// initial value: 0xffff
// reverse input and output
// toggle all output bits
if(!CRC_CCITT16)
CRC_CCITT16 = CRCCreate(16, 0x1021, 0xffff, true, true, 0xffff);
...
CRC_t crc16;
// calculate CRC
crc16 = CRC(CRC_CCITT16, buf, len);
#include "CRC.h"
// 16bits
// polynom is x^{16} + x^{12} + x^5 + 1
// CRC initial value: 0xffff
// reflect input and output
// toggle all output bits
static CRChandle_t CRC_CCITT16 = {
.CRCbits = 16,
.CRCpad = 0,
.Polynom = 0x1021,
.Init = 0xffff,
.XOrOut = 0xffff,
.RefIn = true,
.RefOut = true,
.Polymask = 0xffff,
.Polytable = {
0x0000, 0x1189, 0x2312, 0x329b, 0x4624, 0x57ad, 0x6536, 0x74bf, 0x8c48, 0x9dc1, 0xaf5a, 0xbed3, 0xca6c, 0xdbe5, 0xe97e, 0xf8f7,
0x1081, 0x0108, 0x3393, 0x221a, 0x56a5, 0x472c, 0x75b7, 0x643e, 0x9cc9, 0x8d40, 0xbfdb, 0xae52, 0xdaed, 0xcb64, 0xf9ff, 0xe876,
0x2102, 0x308b, 0x0210, 0x1399, 0x6726, 0x76af, 0x4434, 0x55bd, 0xad4a, 0xbcc3, 0x8e58, 0x9fd1, 0xeb6e, 0xfae7, 0xc87c, 0xd9f5,
0x3183, 0x200a, 0x1291, 0x0318, 0x77a7, 0x662e, 0x54b5, 0x453c, 0xbdcb, 0xac42, 0x9ed9, 0x8f50, 0xfbef, 0xea66, 0xd8fd, 0xc974,
0x4204, 0x538d, 0x6116, 0x709f, 0x0420, 0x15a9, 0x2732, 0x36bb, 0xce4c, 0xdfc5, 0xed5e, 0xfcd7, 0x8868, 0x99e1, 0xab7a, 0xbaf3,
0x5285, 0x430c, 0x7197, 0x601e, 0x14a1, 0x0528, 0x37b3, 0x263a, 0xdecd, 0xcf44, 0xfddf, 0xec56, 0x98e9, 0x8960, 0xbbfb, 0xaa72,
0x6306, 0x728f, 0x4014, 0x519d, 0x2522, 0x34ab, 0x0630, 0x17b9, 0xef4e, 0xfec7, 0xcc5c, 0xddd5, 0xa96a, 0xb8e3, 0x8a78, 0x9bf1,
0x7387, 0x620e, 0x5095, 0x411c, 0x35a3, 0x242a, 0x16b1, 0x0738, 0xffcf, 0xee46, 0xdcdd, 0xcd54, 0xb9eb, 0xa862, 0x9af9, 0x8b70,
0x8408, 0x9581, 0xa71a, 0xb693, 0xc22c, 0xd3a5, 0xe13e, 0xf0b7, 0x0840, 0x19c9, 0x2b52, 0x3adb, 0x4e64, 0x5fed, 0x6d76, 0x7cff,
0x9489, 0x8500, 0xb79b, 0xa612, 0xd2ad, 0xc324, 0xf1bf, 0xe036, 0x18c1, 0x0948, 0x3bd3, 0x2a5a, 0x5ee5, 0x4f6c, 0x7df7, 0x6c7e,
0xa50a, 0xb483, 0x8618, 0x9791, 0xe32e, 0xf2a7, 0xc03c, 0xd1b5, 0x2942, 0x38cb, 0x0a50, 0x1bd9, 0x6f66, 0x7eef, 0x4c74, 0x5dfd,
0xb58b, 0xa402, 0x9699, 0x8710, 0xf3af, 0xe226, 0xd0bd, 0xc134, 0x39c3, 0x284a, 0x1ad1, 0x0b58, 0x7fe7, 0x6e6e, 0x5cf5, 0x4d7c,
0xc60c, 0xd785, 0xe51e, 0xf497, 0x8028, 0x91a1, 0xa33a, 0xb2b3, 0x4a44, 0x5bcd, 0x6956, 0x78df, 0x0c60, 0x1de9, 0x2f72, 0x3efb,
0xd68d, 0xc704, 0xf59f, 0xe416, 0x90a9, 0x8120, 0xb3bb, 0xa232, 0x5ac5, 0x4b4c, 0x79d7, 0x685e, 0x1ce1, 0x0d68, 0x3ff3, 0x2e7a,
0xe70e, 0xf687, 0xc41c, 0xd595, 0xa12a, 0xb0a3, 0x8238, 0x93b1, 0x6b46, 0x7acf, 0x4854, 0x59dd, 0x2d62, 0x3ceb, 0x0e70, 0x1ff9,
0xf78f, 0xe606, 0xd49d, 0xc514, 0xb1ab, 0xa022, 0x92b9, 0x8330, 0x7bc7, 0x6a4e, 0x58d5, 0x495c, 0x3de3, 0x2c6a, 0x1ef1, 0x0f78
}};
...
CRC_t crc16;
// calculate CRC
crc16 = CRC(&CRC_CCITT16, buf, len);
#include "CRC.h"
...
CRChandle_t *CRC_CCITT16;
char *ccode;
// create CRC table for smart message protocol (SML):
// 16bits
// polynom is x^{16} + x^{12} + x^5 + 1
// initial value: 0xffff
// reverse input and output
// toggle all output bits
CRC_CCITT16 = CRCCreate(16, 0x1021, 0xffff, true, true, 0xffff);
// dump the CRC
ccode = CRCdump(CRC_CCITT16);
ESP_LOGI("CRC", "%s", ccode);
// cleanup
free(ccode);
CRCDestroy(CRC_CCITT16);
import CRC
...
CRC_42f0e1eba9ea3693 = CRC_c(64, 0x42f0e1eba9ea3693, 0xffffffffffffffff, 0xffffffffffffffff, True, True, 0xffffffffffffffff, 0,
0x0000000000000000, 0xb32e4cbe03a75f6f, 0xf4843657a840a05b, 0x47aa7ae9abe7ff34, 0x7bd0c384ff8f5e33, 0xc8fe8f3afc28015c,
0x8f54f5d357cffe68, 0x3c7ab96d5468a107, 0xf7a18709ff1ebc66, 0x448fcbb7fcb9e309, 0x0325b15e575e1c3d, 0xb00bfde054f94352,
0x8c71448d0091e255, 0x3f5f08330336bd3a, 0x78f572daa8d1420e, 0xcbdb3e64ab761d61, 0x7d9ba13851336649, 0xceb5ed8652943926,
0x891f976ff973c612, 0x3a31dbd1fad4997d, 0x064b62bcaebc387a, 0xb5652e02ad1b6715, 0xf2cf54eb06fc9821, 0x41e11855055bc74e,
0x8a3a2631ae2dda2f, 0x39146a8fad8a8540, 0x7ebe1066066d7a74, 0xcd905cd805ca251b, 0xf1eae5b551a2841c, 0x42c4a90b5205db73,
0x056ed3e2f9e22447, 0xb6409f5cfa457b28, 0xfb374270a266cc92, 0x48190ecea1c193fd, 0x0fb374270a266cc9, 0xbc9d3899098133a6,
0x80e781f45de992a1, 0x33c9cd4a5e4ecdce, 0x7463b7a3f5a932fa, 0xc74dfb1df60e6d95, 0x0c96c5795d7870f4, 0xbfb889c75edf2f9b,
0xf812f32ef538d0af, 0x4b3cbf90f69f8fc0, 0x774606fda2f72ec7, 0xc4684a43a15071a8, 0x83c230aa0ab78e9c, 0x30ec7c140910d1f3,
0x86ace348f355aadb, 0x3582aff6f0f2f5b4, 0x7228d51f5b150a80, 0xc10699a158b255ef, 0xfd7c20cc0cdaf4e8, 0x4e526c720f7dab87,
0x09f8169ba49a54b3, 0xbad65a25a73d0bdc, 0x710d64410c4b16bd, 0xc22328ff0fec49d2, 0x85895216a40bb6e6, 0x36a71ea8a7ace989,
0x0adda7c5f3c4488e, 0xb9f3eb7bf06317e1, 0xfe5991925b84e8d5, 0x4d77dd2c5823b7ba, 0x64b62bcaebc387a1, 0xd7986774e864d8ce,
0x90321d9d438327fa, 0x231c512340247895, 0x1f66e84e144cd992, 0xac48a4f017eb86fd, 0xebe2de19bc0c79c9, 0x58cc92a7bfab26a6,
0x9317acc314dd3bc7, 0x2039e07d177a64a8, 0x67939a94bc9d9b9c, 0xd4bdd62abf3ac4f3, 0xe8c76f47eb5265f4, 0x5be923f9e8f53a9b,
0x1c4359104312c5af, 0xaf6d15ae40b59ac0, 0x192d8af2baf0e1e8, 0xaa03c64cb957be87, 0xeda9bca512b041b3, 0x5e87f01b11171edc,
0x62fd4976457fbfdb, 0xd1d305c846d8e0b4, 0x96797f21ed3f1f80, 0x2557339fee9840ef, 0xee8c0dfb45ee5d8e, 0x5da24145464902e1,
0x1a083bacedaefdd5, 0xa9267712ee09a2ba, 0x955cce7fba6103bd, 0x267282c1b9c65cd2, 0x61d8f8281221a3e6, 0xd2f6b4961186fc89,
0x9f8169ba49a54b33, 0x2caf25044a02145c, 0x6b055fede1e5eb68, 0xd82b1353e242b407, 0xe451aa3eb62a1500, 0x577fe680b58d4a6f,
0x10d59c691e6ab55b, 0xa3fbd0d71dcdea34, 0x6820eeb3b6bbf755, 0xdb0ea20db51ca83a, 0x9ca4d8e41efb570e, 0x2f8a945a1d5c0861,
0x13f02d374934a966, 0xa0de61894a93f609, 0xe7741b60e174093d, 0x545a57dee2d35652, 0xe21ac88218962d7a, 0x5134843c1b317215,
0x169efed5b0d68d21, 0xa5b0b26bb371d24e, 0x99ca0b06e7197349, 0x2ae447b8e4be2c26, 0x6d4e3d514f59d312, 0xde6071ef4cfe8c7d,
0x15bb4f8be788911c, 0xa6950335e42fce73, 0xe13f79dc4fc83147, 0x521135624c6f6e28, 0x6e6b8c0f1807cf2f, 0xdd45c0b11ba09040,
0x9aefba58b0476f74, 0x29c1f6e6b3e0301b, 0xc96c5795d7870f42, 0x7a421b2bd420502d, 0x3de861c27fc7af19, 0x8ec62d7c7c60f076,
0xb2bc941128085171, 0x0192d8af2baf0e1e, 0x4638a2468048f12a, 0xf516eef883efae45, 0x3ecdd09c2899b324, 0x8de39c222b3eec4b,
0xca49e6cb80d9137f, 0x7967aa75837e4c10, 0x451d1318d716ed17, 0xf6335fa6d4b1b278, 0xb199254f7f564d4c, 0x02b769f17cf11223,
0xb4f7f6ad86b4690b, 0x07d9ba1385133664, 0x4073c0fa2ef4c950, 0xf35d8c442d53963f, 0xcf273529793b3738, 0x7c0979977a9c6857,
0x3ba3037ed17b9763, 0x888d4fc0d2dcc80c, 0x435671a479aad56d, 0xf0783d1a7a0d8a02, 0xb7d247f3d1ea7536, 0x04fc0b4dd24d2a59,
0x3886b22086258b5e, 0x8ba8fe9e8582d431, 0xcc0284772e652b05, 0x7f2cc8c92dc2746a, 0x325b15e575e1c3d0, 0x8175595b76469cbf,
0xc6df23b2dda1638b, 0x75f16f0cde063ce4, 0x498bd6618a6e9de3, 0xfaa59adf89c9c28c, 0xbd0fe036222e3db8, 0x0e21ac88218962d7,
0xc5fa92ec8aff7fb6, 0x76d4de52895820d9, 0x317ea4bb22bfdfed, 0x8250e80521188082, 0xbe2a516875702185, 0x0d041dd676d77eea,
0x4aae673fdd3081de, 0xf9802b81de97deb1, 0x4fc0b4dd24d2a599, 0xfceef8632775faf6, 0xbb44828a8c9205c2, 0x086ace348f355aad,
0x34107759db5dfbaa, 0x873e3be7d8faa4c5, 0xc094410e731d5bf1, 0x73ba0db070ba049e, 0xb86133d4dbcc19ff, 0x0b4f7f6ad86b4690,
0x4ce50583738cb9a4, 0xffcb493d702be6cb, 0xc3b1f050244347cc, 0x709fbcee27e418a3, 0x3735c6078c03e797, 0x841b8ab98fa4b8f8,
0xadda7c5f3c4488e3, 0x1ef430e13fe3d78c, 0x595e4a08940428b8, 0xea7006b697a377d7, 0xd60abfdbc3cbd6d0, 0x6524f365c06c89bf,
0x228e898c6b8b768b, 0x91a0c532682c29e4, 0x5a7bfb56c35a3485, 0xe955b7e8c0fd6bea, 0xaeffcd016b1a94de, 0x1dd181bf68bdcbb1,
0x21ab38d23cd56ab6, 0x9285746c3f7235d9, 0xd52f0e859495caed, 0x6601423b97329582, 0xd041dd676d77eeaa, 0x636f91d96ed0b1c5,
0x24c5eb30c5374ef1, 0x97eba78ec690119e, 0xab911ee392f8b099, 0x18bf525d915feff6, 0x5f1528b43ab810c2, 0xec3b640a391f4fad,
0x27e05a6e926952cc, 0x94ce16d091ce0da3, 0xd3646c393a29f297, 0x604a2087398eadf8, 0x5c3099ea6de60cff, 0xef1ed5546e415390,
0xa8b4afbdc5a6aca4, 0x1b9ae303c601f3cb, 0x56ed3e2f9e224471, 0xe5c372919d851b1e, 0xa26908783662e42a, 0x114744c635c5bb45,
0x2d3dfdab61ad1a42, 0x9e13b115620a452d, 0xd9b9cbfcc9edba19, 0x6a978742ca4ae576, 0xa14cb926613cf817, 0x1262f598629ba778,
0x55c88f71c97c584c, 0xe6e6c3cfcadb0723, 0xda9c7aa29eb3a624, 0x69b2361c9d14f94b, 0x2e184cf536f3067f, 0x9d36004b35545910,
0x2b769f17cf112238, 0x9858d3a9ccb67d57, 0xdff2a94067518263, 0x6cdce5fe64f6dd0c, 0x50a65c93309e7c0b, 0xe388102d33392364,
0xa4226ac498dedc50, 0x170c267a9b79833f, 0xdcd7181e300f9e5e, 0x6ff954a033a8c131, 0x28532e49984f3e05, 0x9b7d62f79be8616a,
0xa707db9acf80c06d, 0x14299724cc279f02, 0x5383edcd67c06036, 0xe0ada17364673f59
])
print('CRC_42f0e1eba9ea3693.CRC(Hello World!): 0x{:x}'.format(CRC_42f0e1eba9ea3693.CRC(b"Hello World!")))
# create CRC table for smart message protocol (SML) once:
# 16bits
# polynom is x^{16} + x^{12} + x^5 + 1
# initial value: 0xffff
# reverse input and output
# toggle all output bits
CRChandle = CRC_c.CRCCreate(16, 0x1021, 0xffff, True, True, 0xffff)
...
crc = CRChandle.CRC(b"12345678")
https://docs.espressif.com/projects/esp-idf/en/latest/esp32/get-started/index.html
Python version ≥ 3
HTML version ≥ 5
http://graphics.stanford.edu/~seander/bithacks.html#BitReverseTable