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DHT & optimizations #2748

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merged 3 commits into from
Nov 18, 2019
Merged

DHT & optimizations #2748

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d6c78cc
[p2p] small optimization
uzi18 Nov 16, 2019
88c6887
[DHT] add extra ms
uzi18 Nov 16, 2019
54bcf2c
[DHT] reoreder interrupt handling
uzi18 Nov 16, 2019
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2 changes: 1 addition & 1 deletion src/_C013.ino
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Original file line number Diff line number Diff line change
Expand Up @@ -166,7 +166,7 @@ void C013_SendUDPTaskData(byte destUnit, byte sourceTaskIndex, byte destTaskInde
const userVarIndex_t userVarIndex = dataReply.sourceTaskIndex * VARS_PER_TASK + x;

if (validUserVarIndex(userVarIndex)) {
dataReply.Values[x] = UserVar[dataReply.sourceTaskIndex * VARS_PER_TASK + x];
dataReply.Values[x] = UserVar[userVarIndex];
}
}

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17 changes: 7 additions & 10 deletions src/_P005_DHT.ino
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Expand Up @@ -151,7 +151,7 @@ bool P005_do_plugin_read(struct EventStruct *event) {
digitalWrite(Plugin_005_DHT_Pin, LOW); // Pull low

switch (Par3) {
case P005_DHT11: delay(18); break; // minimum 18ms
case P005_DHT11: delay(19); break; // minimum 18ms
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I always get a bit nervous by these kind of fixes.
Delay from 18 to 19 msec....
If this really is needed, then the timing is way too critical.

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@uzi18 uzi18 Nov 16, 2019 •
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we discussed this once, it should be 18 minimum, so 19 is not big deal, for dht22 minimum is 1ms and 2ms works ok,
actually it is hard to buy dht11

in fact in one wire protocols timings are critical

we can add delay(0) before turning of interrupts, what do you think?

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we can add delay(0) before turning of interrupts, what do you think?

That sounds like a good idea.

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@TD-er about 1ms more, it is also better for longer wires

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@TD-er bad idea with delay, because we have already delays just before

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Well, it depends, is the delay from the switch statement just critical as minimum, or also for the maximum?

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@TD-er first delay is start condition - request for data and it is minimum critical, every next should not be more than in documentation so critical for maximum.
we still don't know how accurate delays are in esp8266 from poor quality boards to nice ones.

case P005_DHT22: delay(2); break; // minimum 1ms
case P005_DHT12: delay(200); break; // minimum 200ms
case P005_AM2301: delayMicroseconds(900); break;
Expand All @@ -172,15 +172,12 @@ bool P005_do_plugin_read(struct EventStruct *event) {
delayMicroseconds(20);
break;
}

if(!P005_waitState(0)) {P005_log(event, P005_error_no_reading); return false; }
if(!P005_waitState(1)) {P005_log(event, P005_error_no_reading); return false; }

noInterrupts();
if(!P005_waitState(0)) {
interrupts();
P005_log(event, P005_error_no_reading);
return false;
}
if(!P005_waitState(0)) {interrupts(); P005_log(event, P005_error_no_reading); return false; }
if(!P005_waitState(1)) {interrupts(); P005_log(event, P005_error_no_reading); return false; }
if(!P005_waitState(0)) {interrupts(); P005_log(event, P005_error_no_reading); return false; }

bool readingAborted = false;
byte dht_dat[5];
for (i = 0; i < 5 && !readingAborted; i++)
Expand All @@ -196,7 +193,7 @@ bool P005_do_plugin_read(struct EventStruct *event) {
if (readingAborted)
return false;

// Checksum calculation is a Rollover Checksum by design!
// Checksum calculation is a Rollover Checksum by design!
byte dht_check_sum = (dht_dat[0] + dht_dat[1] + dht_dat[2] + dht_dat[3]) & 0xFF; // check check_sum
if (dht_dat[4] != dht_check_sum)
{
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