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README.md: reflect the API changes

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Kosma Moczek 2014-04-27 16:44:56 +02:00
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README.md
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@ -26,22 +26,22 @@ Adding support for more sentences is trivial; see ``minmea.c`` source.
## Fractional number format
Internally, minmea stores fractional numbers as pairs of two integers: ``(value, scale)``.
For example, a value of ``"-123.456"`` would be parsed as ``(-123456, 1000)``. As this
format is quite unwieldy, minmea provides the following convenience macros for converting
Internally, minmea stores fractional numbers as pairs of two integers: ``{value, scale}``.
For example, a value of ``"-123.456"`` would be parsed as ``{-123456, 1000}``. As this
format is quite unwieldy, minmea provides the following convenience functions for converting
to either fixed-point or floating-point format:
* ``minmea_rescale(-123456, 1000, 10) => -1235``
* ``minmea_float(-123456, 1000) => -123.456``
* ``minmea_rescale({-123456, 1000}, 10) => -1235``
* ``minmea_float({-123456, 1000}) => -123.456``
## Coordinate format
NMEA uses the clunky ``DDMM.MMMM`` format which, honestly, is not good in the internet era.
Internally, minmea stores it as a fractional number (see above); for practical uses,
the value should be probably converted to the DD.DDDDD floating point format using the
following macro:
following function:
* ``minmea_coord(-375165, 100) => -37.860832``
* ``minmea_tocoord({-375165, 100}) => -37.860832``
The library doesn't perform this conversion automatically for the following reasons:
@ -59,35 +59,35 @@ The library doesn't perform this conversion automatically for the following reas
case MINMEA_SENTENCE_RMC: {
struct minmea_sentence_rmc frame;
if (minmea_parse_rmc(&frame, line)) {
printf("+++ raw coordinates and speed: (%d/%d,%d/%d) %d/%d\n",
frame.latitude, frame.latitude_scale,
frame.longitude, frame.longitude_scale,
frame.speed, frame.speed_scale);
printf("+++ fixed-point coordinates and speed scaled to three decimal places: (%d,%d) %d\n",
minmea_rescale(frame.latitude, frame.latitude_scale, 1000),
minmea_rescale(frame.longitude, frame.longitude_scale, 1000),
minmea_rescale(frame.speed, frame.speed_scale, 1000));
printf("+++ floating point degree coordinates and speed: (%f,%f) %f\n",
minmea_coord(frame.latitude, frame.latitude_scale),
minmea_coord(frame.longitude, frame.longitude_scale),
minmea_float(frame.speed, frame.speed_scale));
printf("$xxRMC: raw coordinates and speed: (%d/%d,%d/%d) %d/%d\n",
frame.latitude.value, frame.latitude.scale,
frame.longitude.value, frame.longitude.scale,
frame.speed.value, frame.speed.scale);
printf("$xxRMC fixed-point coordinates and speed scaled to three decimal places: (%d,%d) %d\n",
minmea_rescale(&frame.latitude, 1000),
minmea_rescale(&frame.longitude, 1000),
minmea_rescale(&frame.speed, 1000));
printf("$xxRMC floating point degree coordinates and speed: (%f,%f) %f\n",
minmea_tocoord(&frame.latitude),
minmea_tocoord(&frame.longitude),
minmea_tofloat(&frame.speed));
}
} break;
case MINMEA_SENTENCE_GGA: {
struct minmea_sentence_gga frame;
if (minmea_parse_gga(&frame, line)) {
printf("$GPGGA: fix quality: %d\n", frame.fix_quality);
printf("$xxGGA: fix quality: %d\n", frame.fix_quality);
}
} break;
case MINMEA_SENTENCE_GSV: {
struct minmea_sentence_gsv frame;
if (minmea_parse_gsv(&frame, line)) {
printf("$GPGSV: message %d of %d\n", frame.msg_nr, frame.total_msgs);
printf("$GPGSV: sattelites in view: %d\n", frame.total_sats);
printf("$xxGSV: message %d of %d\n", frame.msg_nr, frame.total_msgs);
printf("$xxGSV: sattelites in view: %d\n", frame.total_sats);
for (int i = 0; i < 4; i++)
printf("$GPGSV: sat nr %d, elevation: %d, azimuth: %d, snr: %d dbm\n",
printf("$xxGSV: sat nr %d, elevation: %d, azimuth: %d, snr: %d dbm\n",
frame.sats[i].nr,
frame.sats[i].elevation,
frame.sats[i].azimuth,