kopia lustrzana https://github.com/pjalocha/esp32-ogn-tracker
20 wiersze
1.1 KiB
C++
20 wiersze
1.1 KiB
C++
#include "nmea.h"
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uint8_t NMEA_Check(uint8_t *NMEA, uint8_t Len) // NMEA check-sum
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{ uint8_t Check=0; // to be calculated over characters between '$' and '*' but _excluding_ those.
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for(uint8_t Idx=0; Idx<Len; Idx++)
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Check^=NMEA[Idx];
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return Check; }
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uint8_t NMEA_AppendCheck(uint8_t *NMEA, uint8_t Len)
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{ uint8_t Check=NMEA_Check(NMEA+1, Len-1); // exclude the starting '$'
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NMEA[Len ]='*'; // add '*'
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uint8_t Digit=Check>>4; NMEA[Len+1] = Digit<10 ? Digit+'0':Digit+'A'-10; // and checksum in hex
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Digit=Check&0xF; NMEA[Len+2] = Digit<10 ? Digit+'0':Digit+'A'-10;
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return 3; } // return number of characters added
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uint8_t NMEA_AppendCheckCRNL(uint8_t *NMEA, uint8_t Len)
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{ uint8_t CheckLen=NMEA_AppendCheck(NMEA, Len); // add *XY
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Len+=CheckLen; NMEA[Len++]='\r'; NMEA[Len++]='\n'; NMEA[Len]=0; // add CR, LF, NL
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return CheckLen+2; }
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