Mirror
/
ardupilot
mirror of https://github.com/ArduPilot/ardupilot
5
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

AP_Math: Commonize the CRC4 method

This commit is contained in:
murata 2019-04-24 15:51:28 +09:00 committed by Tom Pittenger
parent 3abe8fed89
commit 7f42be5d3e
2 changed files with 32 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

31
libraries/AP_Math/crc.cpp
View File

@ -19,6 +19,37 @@
#include <stdint.h>
#include "crc.h"
/**
* crc4 method from datasheet for 16 bytes (8 short values)
*
* @param [in] data
* @return crc4
*/
uint16_t crc_crc4(uint16_t *data)
{
uint16_t n_rem = 0;
uint8_t n_bit;
for (uint8_t cnt = 0; cnt < 16; cnt++) {
/* uneven bytes */
if (cnt & 1) {
n_rem ^= (uint8_t)((data[cnt >> 1]) & 0x00FF);
} else {
n_rem ^= (uint8_t)(data[cnt >> 1] >> 8);
}
for (n_bit = 8; n_bit > 0; n_bit--) {
if (n_rem & 0x8000) {
n_rem = (n_rem << 1) ^ 0x3000;
} else {
n_rem = (n_rem << 1);
}
}
}
return (n_rem >> 12) & 0xF;
}
static const uint8_t crc8_table[] = {
0x00, 0x07, 0x0e, 0x09, 0x1c, 0x1b, 0x12, 0x15, 0x38, 0x3f, 0x36, 0x31,
0x24, 0x23, 0x2a, 0x2d, 0x70, 0x77, 0x7e, 0x79, 0x6c, 0x6b, 0x62, 0x65,

1
libraries/AP_Math/crc.h
View File

@ -17,6 +17,7 @@
*/
#pragma once
uint16_t crc_crc4(uint16_t *data);
uint8_t crc_crc8(const uint8_t *p, uint8_t len);
uint16_t crc_xmodem_update(uint16_t crc, uint8_t data);
uint16_t crc_xmodem(const uint8_t *data, uint16_t len);