ESP32 - Wifi hotspots - and RTC modules

@ajpatrick

I haven't used BLE or the ESP32, but if you have a smart phone with BLE, perhaps you could just request the time directly from the phone instead of requiring a network connection.

@will Thanks for the suggestion. I will do some reading now to see if i can learn more about that approach in case it proves easier than trying to get this wifi solution working.

@ajpatrick Maybe I am misremembering but isn't the entire point of a RTC to remember the time as long as it has power? You set it once and as long as the battery in it is good the clock is accurate. I think the batteries are good for a couple years. That means setting the clock should be done once in the setup.

I will look at giving this a try tomorrow.

@zander Hi Ron,

You are right, and that was the original design. no wifi or bluetooth, just the RTC set when the program was uploaded. But if i am giving it to someone else, who may leave the school or move away etc. and the battery fails they have no way of setting the time without getting the source code, and uploading it again. if it was just for me, i don't actually need to change it, but because i will be giving it to someone i don't want it to be difficult to use if the is an issue, like the time being wrong, because it is the main component of the whole device, without an accurate time the tickets are useless. so i am just being careful really.  I don't want it to check the ntp unless there is wifi connection avaiable is what i was thinking. so the teacher sees the time is wrong, presses a button which connects it to their phone and grabs the time, stores it in the rtc, then the device is good to go for months hopefully. does that make sense? i might not be being very clear sorry.

@ajpatrick My understanding is the time only has to be set once then as long as the battery is good it remains accurate. That means putting the code in the setup.

I will be happy to look at it but was up early, had a liquid lunch and too out of it now to concentrate.

Maybe if you can show us what is wrong, a screen shot is always best otherwise it's a bit of a guessing game.

@zander certainly no rush to reply, i am greatful for any help, it doesn't have to be immediate. Perhaps if i rephrase the whole thing like this;

I currently have a device which consists of a thermal printer, an esp32, a ds3231 rtc, a button and a battery pack of 6x1.5v AA batteries.

When powered on, the esp32 responds to the button being pressed and prints out a ticket with some fixed info plus the current time and date.

this works well. when the battery fails i can replace it, re-upload the original code with the new time and it will be good for a year or two apart from replacing the AA batteries that run the printer and esp32.

a friend has asked me to make them one, and i am reluctant to do so unless i can work out a way to make resetting the time on the rtc after battery failure much easier. If they replace the battery the time will be wrong, and they aren't comfortable getting code and uploading it etc. so i am looking for a way that makes resetting the RTC painless. that is perhaps a more succinct way of putting it. My current attempt sees me adding a button which when pressed connects to my phone and grabs the time, but this isnt working properly and causing other issues. below is my working original code without any wifi stuff.

given it is on an esp32, i assume the solution would be either via wifi or bluetooth but i have no knowledge of either, and little enough of any coding.

i hope this makes the issue more clear and removes the confusion of my failed attempts and the subsequent issues.

#include "Adafruit_Thermal.h"
#include "SoftwareSerial.h"
#include "Wire.h"
#include "RTClib.h"

#define TX_PIN 1 // DFRobot GREEN WIRE labeled RX on printer
#define RX_PIN 2 // DFRobot YELLOW WIRE labeled TX on printer
#define btnPin1 4
SoftwareSerial mySerial(RX_PIN, TX_PIN); // Declare SoftwareSerial obj first
Adafruit_Thermal printer(&mySerial); // Pass addr to printer constructor





RTC_DS3231 rtc;

void setup() {
pinMode(btnPin1,INPUT_PULLUP);
// DFRobot BLUE WIRE TO 27
pinMode(27, OUTPUT); digitalWrite(27, LOW);

mySerial.begin(9600);


printer.begin(); // Init printer (same regardless of serial type)
printer.println(F("------------------------------"));

printer.sleep(); // Tell printer to sleep
delay(3000L); // Sleep for 3 seconds
printer.wake(); // MUST wake() before printing again, even if reset
printer.setDefault(); // Restore printer to default


// SETUP RTC MODULE
if (! rtc.begin()) {
printer.println("Couldn't find RTC");
while (1);
}
// rtc.adjust(DateTime(F(__DATE__), F(__TIME__)));
}

void loop() {
DateTime now = rtc.now();
int Push_button_state = digitalRead(btnPin1);
if ( Push_button_state == LOW ){
printer.println(F("------------------------------"));
printer.println(F(""));
printer.setSize('M');
printer.justify('C');
printer.println(F("OUT-OF-CLASS-PASS"));
printer.setSize('L');
printer.print(F("Date: "));
printer.print(now.day(), DEC);
printer.print("/");
printer.print(now.month(), DEC);
printer.println(F(""));
printer.setSize('M');
printer.println(F("This student has permission to"));
printer.println(F("leave the classroom."));
printer.justify('C');
char buffer [25];
uint8_t sec, min, hour;
sec = now.second();
min = now.minute();
hour = now.hour();
sprintf (buffer, "Left class at: %02u:%02u\n", hour, min);
printer.print (buffer);
printer.println(F("Pass valid for 5 minutes."));
printer.justify('L');
printer.println(F("Thank you,"));
printer.justify('C');
printer.doubleHeightOn();
printer.println(F(" MR. PATRICK "));
printer.println(F(""));
printer.doubleHeightOff();
printer.println(F(""));
printer.println(F("------------------------------"));
}
}

@ajpatrick 

You'll still have a problem with WIFI unless you and your friend use the same ID and password.

The RTC I acquire from HiLegto on amazon seem to be stable and operate rather reliably in the use I have for them (RPi B, B+, 4; not have had a need for the Pico yet).

Two pieces that have seemed to have gone unmentioned:  "https://www.nist.gov" and Cron in what I sense to be your quest for an accurate time source.

Since you have covered all the other thoughts I might have had what about the two I mentioned.

NIST offers time for free 24/7/365.  Maybe like me you have COTS clocks sitting around doing little or nothing more than collecting dust.  If you do, you may have an instant resource to use as your accurate time source.  Most of the "Atomic" clocks have an extremely sensitive receiver and a very accurate time piece.  My recollection is the internet has many examples how one might access the innards of the "Atomic" clock to collect the time you want IF you are into hardware.

Cron is an extremely useful piece of software if you might be using a chip that has a linux flavor O/S.  It can be optioned to start at power up; it can be left running in the background; and it can launch other software when properly setup and optioned.

I think the RTC is the better of the choices if the verion being used is correctly setUp and properly optioned along with a fresh powerCell.

NTP would be my second choice though it does require a network connection to be of any value.

If you are into hardware and have available an "Atomic" clock that uses the NIST time stardard (the Navy has another one that is a whole lot more interesting that includes the air almanac) I would be inclined to give it a try since the writeUp suggest something stationary without "largness" restrictions.

Finally, I know nothing about an ESP-32.  I am learning Python and the RPi Pico.  I prefer 'c', assembler, Java ... !  So whatever has been written by me is at best something to be taken under advisement with maybe a grain of salt!

Possibly, this might in someway jiggle a thought?

@will Will is 100% correct, you @ajpatrick think you have a code or perhaps an implementation issue,, but in fact you have a design issue.

If you want to base the design on local time of day you need a way to enter a time when the CR2032 dies after a couple of years.

OR

If a 'rough' time will suffice, say +- a minute then forget WiFi or any radio method of getting the time and just enter it by keyboard. Yes you need to connect a keyboard every couple years so that is the 'con' of that method.

Maybe there is a photographic method,

Maybe an RFID method,

others?

@will i can set this up for them initially, but of course the problem will still be there if they ever change their hotspot details. i am thinking a webserver in softap mode might be a way around that eventually so when it turns on if there are no ssid and pass details saved it will create a soft ap, then they could login to it, set the wifi details, restart and it will connect to their phone and update. but that is well above my head right now.

edit; this would also be a way of setting the time, but i have no idea how to take entries in a web server and use them to set the rtc. there are several possible solutions all of which i currently lack the knowledge for, but that is of course the whole point of the process.

In terms of design issue, oh yeah, this is very true. one of the things i love about getting others involved is the different ways to solve a problem that become apparent. Its a fantastic process i think, and as a teacher, i love getting those 'aha!' moments myself just as much as i love seeing kids have them in class. 🙂

Posted by: @ajpatrick

@will i can set this up for them initially, but of course the problem will still be there if they ever change their hotspot details.

They may not be so eager to share passwords 🙂

@zander FYI @ajpatrick

Ron, have you ever used BLE ? Could it connect to a smart phone and request the time from it ? Everybody has a cell phone now, and they always reset their internal time regularly, so it seems like it may provide a potential cure for resetting the time.

@will No BLE experience. I am thinking WiFiMgr, that way no need to know creds up front. MNy WiFi is super flaky right now but check Bill's video on how to add WiFiMgr to any existing sketch. NOTE, ALL the wifi code needs to be in the setup section NOT the loop. Once the RTC is init it is good for a couple years. See 23:59

@zander FYI @ajpatrick

Wouldn't that require all of the people wanting to use the sketch having to upload their info to keep it all private ?

And, unless it becomes officially cancelled (let us hope), there's still Daylight Saving Time to consider requiring a time change twice a year, or else that needs to be built into the sketch.