From 67a5fad15f1fff43e476671d7381d36e5c2b54c5 Mon Sep 17 00:00:00 2001 From: flo-x <7840512+flo-x@users.noreply.github.com> Date: Sat, 20 May 2023 21:56:35 +0200 Subject: [PATCH] Compare time differences instead of timestamps Comparing two results of millis() can result in erroneous behavior when the value of millis() wraps around, which happens after around 25 days of uptime. Comparing time difference (by subtracting two timestamps) works well, provided timestamps are not too old (less than 25 days old). --- main/ZsensorADC.ino | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/main/ZsensorADC.ino b/main/ZsensorADC.ino index fd8c87497c..862e592f60 100644 --- a/main/ZsensorADC.ino +++ b/main/ZsensorADC.ino @@ -34,6 +34,8 @@ ADC_MODE(ADC_TOUT); # endif +static int persistedadc = -1024; // so that the first reading will always be published + //Time used to wait for an interval before resending adc value unsigned long timeadc = 0; unsigned long timeadcpub = 0; @@ -42,13 +44,12 @@ void setupADC() { } void MeasureADC() { - if (millis() > (timeadc + TimeBetweenReadingADC)) { //retrieving value of temperature and humidity of the box from DHT every xUL + if (millis() - timeadc > TimeBetweenReadingADC) { //retrieving value of temperature and humidity of the box from DHT every xUL # if defined(ESP8266) yield(); analogRead(ADC_GPIO); //the reliability of the readings can be significantly improved by discarding an initial reading and then averaging the results # endif timeadc = millis(); - static int persistedadc; int val = analogRead(ADC_GPIO); int sum_val = val; if (NumberOfReadingsADC > 1) { // add extra measurement for accuracy @@ -60,7 +61,7 @@ void MeasureADC() { if (isnan(val)) { Log.error(F("Failed to read from ADC !" CR)); } else { - if (val >= persistedadc + ThresholdReadingADC || val <= persistedadc - ThresholdReadingADC || (MinTimeInSecBetweenPublishingADC > 0 && millis() > (timeadcpub + (MinTimeInSecBetweenPublishingADC * 1000UL)))) { + if (val >= persistedadc + ThresholdReadingADC || val <= persistedadc - ThresholdReadingADC || (MinTimeInSecBetweenPublishingADC > 0 && millis() - timeadcpub > (MinTimeInSecBetweenPublishingADC * 1000UL))) { timeadcpub = millis(); Log.trace(F("Creating ADC buffer" CR)); StaticJsonDocument jsonBuffer;