Questions tagged [rtc]

Questions regarding Real Time Clocks (RTCs) which can be a timekeeper IC used by microcontrollers, or using a microcontroller as an accurate timekeeper. Some have calendar, alarm, interrupt or heartbeat features, while some simply keep track of time since last programmed (Epoch timers are similar).

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49 views

RTC with ATmega 32 & ds1307 showing the year completely wrong

I have this project to build a clock / calendar with ATmega and ds1307 showing it on a 20*4 LCD (LM044L). I have implemented the code showing the time correctly, i have initialized the RTC too, but ...
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52 views

Bit-bang I2C implement on DS1307 and Atmega328P problem

I currently implement I2C bit-bang for Master Arduino (AVR) to Read/Write to Arduino Slave using Wire.h and DS1307 RTC. My bit-bang i2c work perfectly with Arduino Slave read 8 bytes without ...
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1answer
83 views

What's wrong with this cable?

I have a circuit with an RTC (DS1307) and an LCD display, both connected to an I2C bus. Because the RTC requires a 5V level (the RTC breakout I use has built-in pullups) I also use a level shifter. ...
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24 views

RV-3028-C7 stuck in POR EEPROM refresh

I just purchased an RV-3028-C7 RTC module and tried to get it working. I2C seems to work, so I can read some registers: ...
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1answer
124 views

How does the RTC of a STM32L0 keep the time accurately when using the LSI as the clock source?

I am working on an application that must keep track of time (using a RTC), and will be uploaded on a STM32L052K8. When I was making my hardware I just assumed that I will use the low speed internal (...
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102 views

MAX32660 rev A2 subsecond count

How do I access the subsecond counter (1/256 second) on the MAX32660 rev A2? I tried reading MXC_RTC->ssec, when busy=0 and ready=1, as suggested in Chapter 9 of ...
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4answers
143 views

Why is NMI commonly pulled high on many ARM SoC schematics?

I've noticed that "AP-NMI" is pulled high on several ARM SoC schematics, and it is pulled high by the real-time clock (RTC) voltage, which is an always-on power domain (battery backup). Why ...
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1answer
69 views

Raspberry PI 4 Compute Wakeup Circuits

on the raspberry PI 3 computer IO boards datasheet it has on page 10 (first sheet) is has the option to connect jumper 13-14 to wake up the computer module by connecting global_en to run_pg run_pg is ...
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1answer
28 views

Abracon AB1805 RTC IC - additional resistance on VBAT pin?

I intend to use Abracon AB1805 RTC in designed device, powered by a CR2032 battery. IC datasheet contains a note: * Total battery series impedance = 1.5k ohms, which may require an external resistor ...
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33 views

Low Temperatures Effect on RTC module

How would low temperatures effect the following RTC module? I'm talking around -20 degrees Celsius. It can be seen on the picture that it uses the DS1307N version, which is industrial (-40 to 80 ...
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68 views

RTC Calibration - ppm Offset to Adjust Clock Rate Faster/Slower, by How Much?

I have a TI MSP432P401R board. I have looked through the various other questions related to RTC calibration and I have not found an answer to this seemingly simple question. The MSP432 SDK driverlib ...
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9 views

MCP7941x battery backup connection

In the datasheet the battery is directly connected to pins 3. But in some breakout boards I see this circuit: simulate this circuit – Schematic created using CircuitLab What is the purpose of ...
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118 views

ESP8266 using DS3231 to wake up from deep sleep

I am using the Arduino IDE to program the ESP8266 and am able to set the time, alarms on the DS3231 and test to see that they are firing. My problem is that I would like to use the SQW output to wake ...
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19 views

Debugging of RTC (Real Time Clock) using MPLAB ICD4 debugger

I have been searching for a process for debugging an RTC section using a debugger called MPLAB ICD4, but I didn't get an exact result from Google. Can you please suggest me the process? And is there ...
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1answer
39 views

Error Real Time Clock implementation AVR microcontroller

I want to create a real-time clock using ATmega328p microcontroller. The microcontroller's frequency is 1 MHz. So, I think I should use timer interrupts in CTC mode to generate interrupt every second. ...
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4answers
105 views

Crystal tolerances and what that means for timer interrupts

I'm developing a system that needs to periodically wake up and perform a process. We're currently targeting for an hourly wake up (give or take, this spec is very loose). The key here is the unit cost ...
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1answer
68 views

Interfacing DS1302 - is the schematic I found correct?

On the following website there is a project of a 7-segment clock, which uses DS1302 as RTC. The DS1302 is connected to the microcontroller in the way that I don't really understand. Can someone please ...
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1answer
93 views

External clock input for Atmel SAMD21

Is it possible to use a 32.768kHz square wave, such as the output from the DS3231 RTC, as an input for something like the SAMD21 microcontroller? I would rather not have to add a crystal to my design ...
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2answers
75 views

RTC circuit supercapacitor charge/discharge doubts

This is my current RTC circuit... Supercapacitor = DXJ-5R5V334U (ELNA)... DXJ-5R5V334U = 0.33F, 5.5V, ESR = 150 Ohms Resistor = 150 ohms 0603 100mW 1% If I consider only the resistor, I have a RC ...
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1answer
60 views

How do I give several classes access to the single RTC on my MCU

I'm writing my first large-ish C++ embedded program on a STM32F413. I've become a reasonably firm believer in object oriented coding but am not particularly knowledgeable. The STM32F413 has one RTC ...
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36 views

Replacing Dallas NVRAM with larger capacity variant?

This DS1225AB-200 (8k x 8 = 64kB NVSRAM) is from 1995 and is probably dead (cannot measure from the outside.) The only close replacement in stock is a DS1230AB-100 (32k x 8 = 256kB.) Looking at the ...
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2answers
116 views

Properly isolating I2C for powered off MCU

What is the proper way to isolate the I2C lines of two devices where one is powered on and the other can be powered down? I'm not 100% sure if isolation is even necessary, but I suspect it is. Here is ...
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69 views

Nano Power Soft Latch

I need to latch an INT output with a time width of 7 ms. This signal is generated by an RTC clock and I need to enable an LDO with it. The LDO powers an MCU, which at the end of its program should be ...
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2answers
99 views

Suspected PIC alarm bug with RTCC module in PIC16LF series, cannot set alarm to 00 seconds

This question is about understanding the functionality of RTCC alarm registers within one PIC family. While I am using 16LF19176, I believe this question relates to all RTCC modules in this family. I ...
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1answer
451 views

How to switch ON raspberry, arduino, esp32, etc from SQW pin of RTC DS3231

My issue is how to build the circuit and what is the most efficient one to trigger a MCU from the Alarm of the RTC DS3231. For the momment I have built the one in the picture bellow (with p-channel ...
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1answer
165 views

RTC time is not kept in Stm32f103 by vbat

I am using stm32f103c8 and External Clock Crystal (LSE). I connected the Vbat with a 1220 coin battery. But when I turn off VDD and turn on the micro again, the time and date are all zero. Why time is ...
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2answers
151 views

Why do most microcontrollers not embed a 32k oscillator?

Why do most embedded systems use an external 32k oscillator?
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2answers
178 views

Crystal Layout for RTC

I require recommendations for the layout of crystal. I am designing a board which uses an external RTC. The Mfr. part number for RTC is PCF8523TK/1,118 and Mouser part number is 771-PCF8523TK/1118. It ...
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2answers
543 views

RTC backup by super capacitor estimation issue

I create a RTC backup circuit for a STM32L412CBT6. Circuit work but not as long as I estimate during design. Here is the schematic (VBKP go directly to STM32 VBAT pin): SC1 capacity is 0.33F Here is ...
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1answer
399 views

Using a DS3231 RTC alarm + MOSFETS to turn on a MCU

I'm using a DS3231 in conjunction with two IRLZ44N MOSFETs to switch power to a MCU when the alarm on the DS3231 triggers. The alarm on the DS3231 pulls the SQW/INT pin to ground and turns on the MCU ...
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25 views

DS3231M Current Consumption

I have bought a DS3231M Real time clock. From the datasheet, one can see that when the RTC is powered from VCC with 3.63V, the max current I_CCA is 200uA when I2C is active, and I_CCS 130uA when I2C ...
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43 views

RTC not Responding

I'm using a MCP7940 with a Atmega328P on a custom board. I'm using the Arduino Wire library. When I first start communication to write the time to the registers, things seem to work fine but then in ...
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1answer
168 views

Is STM32 RTC halted during debug or not?

I'm working with STM32F411RE but I presume the problem is the same for any STM32F, and possibly others. I couldn't find in the reference manual whether or not the RTC is halted during a debug session....
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2answers
63 views

small inexpensive battery powerable component for daily timer circuit with LED and button

I want to make a small "visual alarm" device that turns on a LED every day at a time (e.g. 17:00) and turns the LED off on button press or (if no button was pressed) at a later time (e.g. 22:00). I ...
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1answer
104 views

Can anyone identify this rtc cmos battery conector please?

I'm trying to find the plug that fits into this socket. It's really, really small like 3.36mm x 4mm and the distance from pin to pin is like 1mm. Is the socket for an RTC BIOS battery in a Up squared ...
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1answer
789 views

What is the STM32 “timestamp” feature designed for?

While browsing the stm32f051xx datasheet I came across this section (p23, section 3.15, Real-time clock (RTC) and backup registers) timestamp feature which can be used to save the calendar content. ...
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1answer
33 views

Overo Waterstorm RTC power usage

I am trying to work out the current draw from Vbackup when the RTC is kept alive but the rest of the system is shutdown. I am trying to determine the size of the backup cell that I need for my ...
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1answer
324 views

STM32 RTC from battery

I have STM32(F103VBT6) and trying to use RTC with battery to keep correct time, but after removing power from DC supply supercap ( Seiko ) loses power almost instantly. How should going to battery be ...
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2answers
52 views

Power On Tracking Integrated Circuit, ON Time Odometer [closed]

How would I realize a I2C/SPI device capable of tracking how long power has been applied over the lifetime of the device? Ideally this would be a 8 pin (or less) SMT part costing around a couple ...
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1answer
40 views

Timer IC that doesn't reset count because of power down and remembers last state [closed]

I'm looking for a timer/RTC that will count how long the system power was up in total and will toggle a pin after a specific time that will be configured in advance. Does a timer that "remembers" ...
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2answers
2k views

How to wake STM32F103 by RTC using HAL libraries / Registers?

I've started digging into STM32F103 using HAL Libraries and raw registers. It's the first time to program at such low level. Anyway following a video I've successfully implemented "Standby" mode. ...
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2answers
308 views

DS1307 RTC module using without arduino?

Is it possible to use RTC module DS1307 to schedule swtiching lights on and off? I am not supposed to use arduino but all tutorials on internet are with arduino. The main problem for me is power ...
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1answer
87 views

Gumstix Overo RTC support?

I’m working on a design incorporating a Gumstix Overo AirSTORM-Y COM, and I note that it can accommodate a backup battery. I understand that this is handled by the on-board TPS65950 PMIC, which ...
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1answer
246 views

Why pick 262144 Hz oscillator frequency?

Some Bulova watches (for example the Precisionist collection) use 262144 Hz crystal oscillators instead of the usual 32768 Hz. What are the true advantages of this higher frequency, if they even exist?...
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96 views

Can I use the main power battery as a RTC battery as well?

Im currently thinking of a Nixie-Watch. Because I have almost no space on my PCB, I would like to use the 3.3v battery which powers the whole system also as the RTC Battery. I could connect a 3.3v ...
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1answer
658 views

Converting Open-Drain to Active-High (low voltage, low power)

In my design, I need an RTC (PCF85263A) to enable a boost converter (TPS61021A) after the RTC alarm triggers an interrupt. The interrupt pin on the RTC (INTA) is open-drain, but the enable pin on the ...
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1answer
63 views

PCF8563 RTC false reading

This my first time to deal with RTC. I forget to add the crystal oscillator to the OSCI of the PCF8563 chip (I thought it has an internal oscillator). Therefore, I had to insert a 32.768kHz (sine wave)...
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63 views

Is the difference in trace lengths why my RTC isnt working?

I am using the PCF8523TS RTC with a 32.768 kHz Crystal. I have tested the smaller package which worked fine with the Adafruit module, but I can't seem to get it to work with the TS package. I either ...
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1answer
411 views

DS3231 stops working on VBAT

So I had a problem with DS3231 not counting time when on VBAT. Also, I had a problem with alarm not resetting after it is triggered. I saw many people on the net having these problems, so below is the ...
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3answers
227 views

DS3234 real time clock reset pin

From the schematic provided for DS3234: It can be seen that the RESET pin is active low, and is connected to unit that provides Vcc. However, if power is disconnected and only Vbat is left, this ...

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