110 lines
3.7 KiB
C
110 lines
3.7 KiB
C
#include <stdio.h>
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#include <stdlib.h>
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#include <stdint.h>
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#include <string.h>
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/* -------------------------------------------------------------------------- */
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/* --- SUBFUNCTIONS DECLARATION --------------------------------------------- */
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static void usage(void);
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uint16_t sx1302_lora_payload_crc(const uint8_t * data, uint8_t size);
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void remove_spaces(char *str);
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/* -------------------------------------------------------------------------- */
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/* --- MAIN FUNCTION -------------------------------------------------------- */
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int main(int argc, char ** argv)
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{
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int j;
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uint8_t payload[255];
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uint8_t payload_size;
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uint16_t crc;
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char hexstr[1024];
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if (argc < 2) {
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usage();
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return -1;
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}
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/* Get payload hex string from command line */
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memcpy(hexstr, argv[1], strlen(argv[1]));
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hexstr[strlen(argv[1])] = '\0';
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printf("Input hex string: %s\n", hexstr);
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/* Remove spaces from the string if any */
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remove_spaces(hexstr);
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hexstr[strlen(hexstr)] = '\0';
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printf("Removing spaces: %s\n", hexstr);
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/* Convert hex string to byte array */
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payload_size = strlen(hexstr) / 2;
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for (j = 0; j < payload_size; j++) {
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sscanf(hexstr + 2*j, "%02hhx", &payload[j]);
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}
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/* Compute CRC */
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crc = sx1302_lora_payload_crc(payload, payload_size);
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printf("Payload CRC_16: %04X\n", crc);
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return 0;
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}
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/* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ */
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void usage(void) {
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printf("Missing payload hex string\n");
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}
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/* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ */
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void remove_spaces(char *str)
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{
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/* To keep track of non-space character count */
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int count = 0;
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/* Traverse the given string. If current character
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is not space, then place it at index 'count++' */
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for (int i = 0; str[i]; i++) {
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if (str[i] != ' ') {
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str[count++] = str[i]; /* here count is incremented */
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}
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}
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str[count] = '\0';
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}
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/* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ */
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void lora_crc16(const char data, int *crc) {
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int next = 0;
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next = (((data>>0)&1) ^ ((*crc>>12)&1) ^ ((*crc>> 8)&1) ) ;
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next += ((((data>>1)&1) ^ ((*crc>>13)&1) ^ ((*crc>> 9)&1) )<<1 ) ;
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next += ((((data>>2)&1) ^ ((*crc>>14)&1) ^ ((*crc>>10)&1) )<<2 ) ;
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next += ((((data>>3)&1) ^ ((*crc>>15)&1) ^ ((*crc>>11)&1) )<<3 ) ;
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next += ((((data>>4)&1) ^ ((*crc>>12)&1) )<<4 ) ;
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next += ((((data>>5)&1) ^ ((*crc>>13)&1) ^ ((*crc>>12)&1) ^ ((*crc>> 8)&1))<<5 ) ;
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next += ((((data>>6)&1) ^ ((*crc>>14)&1) ^ ((*crc>>13)&1) ^ ((*crc>> 9)&1))<<6 ) ;
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next += ((((data>>7)&1) ^ ((*crc>>15)&1) ^ ((*crc>>14)&1) ^ ((*crc>>10)&1))<<7 ) ;
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next += ((((*crc>>0)&1) ^ ((*crc>>15)&1) ^ ((*crc>>11)&1) )<<8 ) ;
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next += ((((*crc>>1)&1) ^ ((*crc>>12)&1) )<<9 ) ;
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next += ((((*crc>>2)&1) ^ ((*crc>>13)&1) )<<10) ;
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next += ((((*crc>>3)&1) ^ ((*crc>>14)&1) )<<11) ;
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next += ((((*crc>>4)&1) ^ ((*crc>>15)&1) ^ ((*crc>>12)&1) ^ ((*crc>> 8)&1))<<12) ;
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next += ((((*crc>>5)&1) ^ ((*crc>>13)&1) ^ ((*crc>> 9)&1) )<<13) ;
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next += ((((*crc>>6)&1) ^ ((*crc>>14)&1) ^ ((*crc>>10)&1) )<<14) ;
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next += ((((*crc>>7)&1) ^ ((*crc>>15)&1) ^ ((*crc>>11)&1) )<<15) ;
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(*crc) = next;
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}
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/* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ */
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uint16_t sx1302_lora_payload_crc(const uint8_t * data, uint8_t size) {
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int i;
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int crc = 0;
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for (i = 0; i < size; i++) {
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lora_crc16(data[i], &crc);
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}
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//printf("CRC16: 0x%02X 0x%02X (%X)\n", (uint8_t)(crc >> 8), (uint8_t)crc, crc);
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return (uint16_t)crc;
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}
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