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Correct handling of millis() rollover 

millis() returns an unsigned long integer, and C++ guarantees that
arithmetics on this type work modulo (ULONG_MAX+1). This behavior
ensures that computing a delay as

    millis() - previousMillis

yields the correct result across millis() rollover events, as long as
the time actually elapsed is less than about 49.7 days.
This commit is contained in:
Edgar Bonet 2020-02-20 19:03:13 +01:00
parent 96625de7d3
commit 939534d580
8 changed files with 12 additions and 25 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
examples/GPS_HardwareSerial_LOCUS_Status/GPS_HardwareSerial_LOCUS_Status.ino
View File

@ -58,7 +58,7 @@ void setup()
Serial.println(" no response :(");
}
uint32_t updateTime = 1000;
uint32_t timer = 0;
void loop() // run over and over again
{
@ -67,9 +67,9 @@ void loop() // run over and over again
if ((c) && (GPSECHO))
Serial.write(c);
if (millis() > updateTime)
if (millis() - timer > 1000)
{
updateTime = millis() + 1000;
timer = millis();
if (GPS.LOCUS_ReadStatus()) {
Serial.print("\n\nLog #");
Serial.print(GPS.LOCUS_serial, DEC);
@ -98,5 +98,5 @@ void loop() // run over and over again
Serial.print((int)GPS.LOCUS_percent); Serial.print("% Used ");
}//if (GPS.LOCUS_ReadStatus())
}//if (millis() > updateTime)
}//if (millis() - timer > 1000)
}//loop

2
examples/GPS_HardwareSerial_Parsing/GPS_HardwareSerial_Parsing.ino
View File

@ -76,8 +76,6 @@ void loop() // run over and over again
if (!GPS.parse(GPS.lastNMEA())) // this also sets the newNMEAreceived() flag to false
return; // we can fail to parse a sentence in which case we should just wait for another
}
// if millis() or timer wraps around, we'll just reset it
if (timer > millis()) timer = millis();
// approximately every 2 seconds or so, print out the current stats
if (millis() - timer > 2000) {

3
examples/GPS_HardwareSerial_Timing/GPS_HardwareSerial_Timing.ino
View File

@ -101,9 +101,6 @@ void loop() // run over and over again
return; // we can fail to parse a sentence in which case we should just
// wait for another
}
// if millis() or timer wraps around, we'll just reset it
if (timer > millis())
timer = millis();
// approximately every 2 seconds or so, random intervals, print out the
// current stats

2
examples/GPS_I2C_Parsing/GPS_I2C_Parsing.ino
View File

@ -64,8 +64,6 @@ void loop() // run over and over again
if (!GPS.parse(GPS.lastNMEA())) // this also sets the newNMEAreceived() flag to false
return; // we can fail to parse a sentence in which case we should just wait for another
}
// if millis() or timer wraps around, we'll just reset it
if (timer > millis()) timer = millis();
// approximately every 2 seconds or so, print out the current stats
if (millis() - timer > 2000) {

8
examples/GPS_SoftwareSerial_LOCUS_Status/GPS_SoftwareSerial_LOCUS_Status.ino
View File

@ -68,7 +68,7 @@ void setup()
}
}
uint32_t updateTime = 1000;
uint32_t timer = 0;
void loop() // run over and over again
{
@ -77,9 +77,9 @@ void loop() // run over and over again
if ((c) && (GPSECHO))
Serial.write(c);
if (millis() > updateTime)
if (millis() - timer > 1000)
{
updateTime = millis() + 1000;
timer = millis();
if (GPS.LOCUS_ReadStatus()) {
Serial.print("\n\nLog #");
Serial.print(GPS.LOCUS_serial, DEC);
@ -108,7 +108,7 @@ void loop() // run over and over again
Serial.print((int)GPS.LOCUS_percent); Serial.print("% Used ");
}//if (GPS.LOCUS_ReadStatus())
}//if (millis() > updateTime)
}//if (millis() - timer > 1000)
}//loop

3
examples/GPS_SoftwareSerial_Parsing/GPS_SoftwareSerial_Parsing.ino
View File

@ -78,9 +78,6 @@ void loop() // run over and over again
return; // we can fail to parse a sentence in which case we should just wait for another
}
// if millis() or timer wraps around, we'll just reset it
if (timer > millis()) timer = millis();
// approximately every 2 seconds or so, print out the current stats
if (millis() - timer > 2000) {
timer = millis(); // reset the timer

9
src/Adafruit_GPS.cpp
View File

@ -637,8 +637,7 @@ bool Adafruit_GPS::wakeup(void) {
/**************************************************************************/
/*!
@brief Time in seconds since the last position fix was obtained. Will
fail by rolling over to zero after one millis() cycle, about 6-1/2 weeks.
@brief Time in seconds since the last position fix was obtained.
@return nmea_float_t value in seconds since last fix.
*/
/**************************************************************************/
@ -648,8 +647,7 @@ nmea_float_t Adafruit_GPS::secondsSinceFix() {
/**************************************************************************/
/*!
@brief Time in seconds since the last GPS time was obtained. Will fail
by rolling over to zero after one millis() cycle, about 6-1/2 weeks.
@brief Time in seconds since the last GPS time was obtained.
@return nmea_float_t value in seconds since last GPS time.
*/
/**************************************************************************/
@ -659,8 +657,7 @@ nmea_float_t Adafruit_GPS::secondsSinceTime() {
/**************************************************************************/
/*!
@brief Time in seconds since the last GPS date was obtained. Will fail
by rolling over to zero after one millis() cycle, about 6-1/2 weeks.
@brief Time in seconds since the last GPS date was obtained.
@return nmea_float_t value in seconds since last GPS date.
*/
/**************************************************************************/

2
src/NMEA_data.cpp
View File

@ -60,7 +60,7 @@ void Adafruit_GPS::newDataValue(nmea_index_t idx, nmea_float_t v) {
// weighting factor for smoothing depends on delta t / tau
nmea_float_t w =
min((nmea_float_t)1.0,
((nmea_float_t)millis() - val[idx].lastUpdate) / val[idx].response);
(nmea_float_t)(millis() - val[idx].lastUpdate) / val[idx].response);
// default smoothing
val[idx].smoothed = (1.0 - w) * val[idx].smoothed + w * v;
// special smoothing for some angle types