/* CRC-7/CRC-16 (XModem) implementation for Cortex M3 * * Written 2010 by Ingo Korb */ .syntax unified .section .text /* uint8_t crc7update(uint8_t crc, const uint8_t data) */ .global crc7update .thumb_func crc7update: mov r2, #8 // number of bits to process lsl r1, r1, #24 // pre-shift data byte to top of word loop: lsl r0, r0, #1 // shift CRC lsls r1, r1, #1 // shift data byte (highest bit now in C) bcc 0f // jump if bit was 0 eor r0, r0, #0x80 // invert top bit of CRC if not 0: tst r0, #0x80 // test top bit of CRC beq 1f // skip if top bit is clear eor r0, r0, #0x09 // apply polinomial 1: subs r2, r2, #1 // decrememt bit cointer bne loop // loop for next bit uxtb r0, r0 // clear top bits of result bx lr // return /* uint16_t crc_xmodem_block(uint16_t crc, uint8_t *data, uint32_t len) */ .global crc_xmodem_block .thumb_func crc_xmodem_block: adr r12, crc_table // load address of crc table blockloop: ldrb.w r3, [r1], #1 // read data byte eor r3, r3, r0, lsr #8 // EOR data byte ldrh r3, [r12, r3, lsl #1] // load value from CRC table eor r0, r3, r0, lsl #8 // update CRC uxth r0, r0 // clear top bits of result subs r2, r2, #1 // decrement length bne blockloop // loop while length > 0 bx lr // return /* uint16_t crc_xmodem_block(uint16_t crc, uint8_t *data, uint32_t len) */ .global crc_xmodem_update .thumb_func crc_xmodem_update: adr r2, crc_table // load address of crc table eor r1, r1, r0, lsr #8 // EOR data byte ldrh r3, [r2, r1, lsl #1] // load value from CRC table eor r0, r3, r0, lsl #8 // update CRC uxth r0, r0 // clear top bits of result bx lr // return crc_table: .short 0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50a5, 0x60c6, 0x70e7 .short 0x8108, 0x9129, 0xa14a, 0xb16b, 0xc18c, 0xd1ad, 0xe1ce, 0xf1ef .short 0x1231, 0x0210, 0x3273, 0x2252, 0x52b5, 0x4294, 0x72f7, 0x62d6 .short 0x9339, 0x8318, 0xb37b, 0xa35a, 0xd3bd, 0xc39c, 0xf3ff, 0xe3de .short 0x2462, 0x3443, 0x0420, 0x1401, 0x64e6, 0x74c7, 0x44a4, 0x5485 .short 0xa56a, 0xb54b, 0x8528, 0x9509, 0xe5ee, 0xf5cf, 0xc5ac, 0xd58d .short 0x3653, 0x2672, 0x1611, 0x0630, 0x76d7, 0x66f6, 0x5695, 0x46b4 .short 0xb75b, 0xa77a, 0x9719, 0x8738, 0xf7df, 0xe7fe, 0xd79d, 0xc7bc .short 0x48c4, 0x58e5, 0x6886, 0x78a7, 0x0840, 0x1861, 0x2802, 0x3823 .short 0xc9cc, 0xd9ed, 0xe98e, 0xf9af, 0x8948, 0x9969, 0xa90a, 0xb92b .short 0x5af5, 0x4ad4, 0x7ab7, 0x6a96, 0x1a71, 0x0a50, 0x3a33, 0x2a12 .short 0xdbfd, 0xcbdc, 0xfbbf, 0xeb9e, 0x9b79, 0x8b58, 0xbb3b, 0xab1a .short 0x6ca6, 0x7c87, 0x4ce4, 0x5cc5, 0x2c22, 0x3c03, 0x0c60, 0x1c41 .short 0xedae, 0xfd8f, 0xcdec, 0xddcd, 0xad2a, 0xbd0b, 0x8d68, 0x9d49 .short 0x7e97, 0x6eb6, 0x5ed5, 0x4ef4, 0x3e13, 0x2e32, 0x1e51, 0x0e70 .short 0xff9f, 0xefbe, 0xdfdd, 0xcffc, 0xbf1b, 0xaf3a, 0x9f59, 0x8f78 .short 0x9188, 0x81a9, 0xb1ca, 0xa1eb, 0xd10c, 0xc12d, 0xf14e, 0xe16f .short 0x1080, 0x00a1, 0x30c2, 0x20e3, 0x5004, 0x4025, 0x7046, 0x6067 .short 0x83b9, 0x9398, 0xa3fb, 0xb3da, 0xc33d, 0xd31c, 0xe37f, 0xf35e .short 0x02b1, 0x1290, 0x22f3, 0x32d2, 0x4235, 0x5214, 0x6277, 0x7256 .short 0xb5ea, 0xa5cb, 0x95a8, 0x8589, 0xf56e, 0xe54f, 0xd52c, 0xc50d .short 0x34e2, 0x24c3, 0x14a0, 0x0481, 0x7466, 0x6447, 0x5424, 0x4405 .short 0xa7db, 0xb7fa, 0x8799, 0x97b8, 0xe75f, 0xf77e, 0xc71d, 0xd73c .short 0x26d3, 0x36f2, 0x0691, 0x16b0, 0x6657, 0x7676, 0x4615, 0x5634 .short 0xd94c, 0xc96d, 0xf90e, 0xe92f, 0x99c8, 0x89e9, 0xb98a, 0xa9ab .short 0x5844, 0x4865, 0x7806, 0x6827, 0x18c0, 0x08e1, 0x3882, 0x28a3 .short 0xcb7d, 0xdb5c, 0xeb3f, 0xfb1e, 0x8bf9, 0x9bd8, 0xabbb, 0xbb9a .short 0x4a75, 0x5a54, 0x6a37, 0x7a16, 0x0af1, 0x1ad0, 0x2ab3, 0x3a92 .short 0xfd2e, 0xed0f, 0xdd6c, 0xcd4d, 0xbdaa, 0xad8b, 0x9de8, 0x8dc9 .short 0x7c26, 0x6c07, 0x5c64, 0x4c45, 0x3ca2, 0x2c83, 0x1ce0, 0x0cc1 .short 0xef1f, 0xff3e, 0xcf5d, 0xdf7c, 0xaf9b, 0xbfba, 0x8fd9, 0x9ff8 .short 0x6e17, 0x7e36, 0x4e55, 0x5e74, 0x2e93, 0x3eb2, 0x0ed1, 0x1ef0 .end