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Index checksum explicitly on $ and * 

parse() Improves slightly on https://github.com/adafruit/Adafruit_GPS/pull/86 by indexing on the position of the $ and the * in the string instead of the beginning and the end of the string.  Does not require sentence string have a particular termination, e.g. CRLF.
This commit is contained in:
sellensr 2019-04-16 19:49:01 -04:00
parent b431f20491
commit 44af8c9086
1 changed files with 6 additions and 7 deletions
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13
Adafruit_GPS.cpp
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@ -57,14 +57,13 @@ boolean Adafruit_GPS::parse(char *nmea) {
// do checksum check // do checksum check
// first look if we even have one // first look if we even have one
size_t len = strlen(nmea); char *ast = strchr(nmea,'*');
if (nmea[len-5] == '*') { if (ast != NULL) {
uint16_t sum = parseHex(nmea[len-4]) * 16; uint16_t sum = parseHex(*(ast+1)) * 16;
sum += parseHex(nmea[len-3]); sum += parseHex(*(ast+2));
// check checksum // check checksum
for (uint8_t i=1; i < (len-5); i++) { for (char *p = strchr(nmea,'$')+1; p < ast; p++) {
sum ^= nmea[i]; sum ^= *p;
} }
if (sum != 0) { if (sum != 0) {
// bad checksum :( // bad checksum :(