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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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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48 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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65 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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112 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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52 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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why i2cdetect -y -r 0 cannot detect all my device under /sys/bus/i2c/devices/i2c-0/

i2cdetect -y -r 0 only shows a 0x70 address. But it show has one more 0x6f address: ...
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1answer
140 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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39 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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60 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
130 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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79 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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digispark + pcf8563 RTC interrupt not working

I have PCF8563 WAVESHARE board connected to DIGISPARK via I2C. Here is the code: ...
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2answers
2k views

STM32 RTC with HAL libraries

I am working on stm32l053 (nucleo 64) and I want to track time with integrated RTC. Since I am quite new to stm32 development I am using CubeMX and HAL libraries. My problem is that the time is not ...
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279 views

DS3231 Real Time Clock i2c 3volt battery 5V arduino

I have a doubt I hope somebody can help me I am thinking to add to my project using Arduino Mega 5V a DS3232 real time clock. I can see on data sheet some information about the MAX voltage for SCL ...
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237 views

RTC DS3231 get reset

The RTC module ZS-042 get suddenly reset and show default values (2000/0/0) with no possibility to change it no matter what. The reset can occur after uploading a new sketch (I'm using ESP32) or while ...
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128 views

How to detect low RTC battery with low extra battery load?

I want to detect low battery in typical DS1307 circuit with microcontroller. My first idea is to connect one of low cost comparator inputs to Vbat, another input to 2.0V from some voltage divider ...
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126 views

Ultra Low Power, LDO Enable from RTC vs. deep sleep MCU interupt

I have a question regarding optimising design for ultra low power consumption device. I'm trying to develop a remote sensor node that should measure and send data every few hours. Currently I have an ...
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87 views

High precision timekeeping

Hey I'm looking for suggestions for implementing a very high precision timekeeping device. I need to record independent signals in multiple devices and then time match them to an accuracy of about ...
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3answers
257 views

32.768kHz crystal making audible noise

I am doing a project to record and log the voltages of an 8 cell lithium battery. The project is based on an STM32 microcontroller, and logging is done on an SD card. I have made the first version of ...
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2answers
322 views

Problem configuring RTC of STM32F4 using LSE

I want to use RTC of STM32F4. When I configure this with LSI, I have no problem. But when I use LSE, I have a timeout error in SystemClock_Config function when it ...
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85 views

STM32F4xx, How to use RTC correctly?

I'm trying to run RTC, but there are two problems. 1) It is impossible to write the security key in the WPR register. 2) It is impossible to set the time and date in the TR and DR registers. I tried ...
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101 views

RTC time advancing

I'm working in some projects with an RTC. I'm using the PCF85063A. The problem is: the RTC counter is advancing from real time about 2 minutes per week. I searched for hardware and firmware errors, ...
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1answer
764 views

Minimalistic RTC backup battery charging or a super-capacitor?

I am trying to provide RTC power backup for a 3.3V system that will be running at the very least 8hrs during the work day. As such I only need up to a month of backup, enough to survive over long ...
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1answer
402 views

Interfacing coin cell back up for internal RTC of ESP32

In esp wroom-32 all the VDD pins has a common connection. It includes VDD_RTC too. So in case of power failure if I switch the power between main DC source and coin cell using a mosfet, will it create ...
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Is a Real-Time Clock (RTC) necessary for real-time systems? [closed]

Assuming that we are working on a real-time Linux system and hardware which consists of high resolution timers, does having an RTC affect the real-timeliness of the system? Here it says that it ...
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2answers
342 views

Use one RTC battery for two circuits

I'm designing a circuit with STM32F407 and a DS3231 chip clock. The MCU has a separate VBat pin that can be used and on the other hand, the DS3231 chip has its own RTC. I'm wondering can I use a ...
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542 views

RTC Power Switch for Raspberry Pi

I have done a lot of research on how to design a circuit to cut power from the pi after a safe shutdown and then turn it back on at a certain time. I am using a DS3231 RTC with an active low ALARM pin ...
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2answers
479 views

32.768 kHz Crystal Troubleshooting

I'm at my wit's end trying to get a 32.768 kHz tuning fork crystal to work and I don't know what I'm doing wrong. First, some background: I'm using a 16MHz crystal in conjunction with an Atmega 328P-...
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1answer
3k views

Stm32 RTC wakeup from standby

I am using an STM32L053C8 and I am trying to set up an RTC wakeup event, and while I am successful, I can only do it to a max time which is a couple of seconds. I need to put it in standby and wake up ...
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47 views

DS1302 maximum current source/sink?

What is the recommended and maximum current sourcing and sinking capability on the DS1302? Is this what's given by "Active Supply Current" in the spec?
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1answer
64 views

Using RTC DS1307 in multiple programs

I'm kinda new to electronics and programming, but I managed to make a DS1307 RTC functional when it is used by only one program (I'm using C code). Buf if I try to use it in multiple programs at the ...
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120 views

where and how to connect battery for RTC of DSPIC33EP512MU814

am working on 144 pin DS PIC am not able to understand how should i connect a battery to RTC of the said pic and which pin of the pic.I need to use internal RTC of the pic
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2answers
2k views

Crystal Oscillator Circuit Design

I am trying to design a real-time clock circuit using a 32.768 KHz oscillator. I have no access to a datasheet for the microcontroller that I am using, but I know it requirese a 330K resistor and an ...
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1k views

STM32 and DS3231 connection

I need to connect real time clock DS3231 to STM32F103C8T6 microcontroller. I connected DS3231 SCL pin to STM32 PB6 pin and SDA pin to PB7. The program code compile was successful, but DS3231 made no ...
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1answer
105 views

Real time clock MCP7940N I2C interface

The RTC MCP7940N is used in the system. The microcontroller and RTC MCP7940N are connected through the I2C interface. I would to know what is the better design to read the timer value from the RTC. ...
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1answer
131 views

slaves interfere when sharing i2c bus line

I'm very new to microcontrollers, and I'm using PIC18F4620 (master) to communicate with the TCS34725 color sensor (slave), and DS1307 real time clock (slave, on board) via I2C. Right now, I'm ...
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91 views

DCF77 - No Signal detected

I'm using a Conrad DCF77 to get RTC on Beaglebone Black and wiring it so: 1--> GND | 2--> VCC 3,3 V | 3--> One of the gpios (P8_11) To read the Signal of the DCF Antenn I wrote the code: ...
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1answer
2k views

Coin cell battery recharging circuit for RTC backup power

I am designing a system that contains an RTC to for displaying the date and time on a user interface, as well as log events with time stamps. In this particular case, the system gets powered-on at ...
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1answer
683 views

STM32 RTC - how to update?

I have a remote unit that runs a STM32L0 MCU. It is not connected to the internet but communicates with a remote PC over radio. I would like to update the RTC on the remote unit with a timestamp that ...
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1answer
102 views

Distinguish between hardware or firmware issue

I'm writing a firmware for CC3220SF from TI using a custom board I've designed. I'm facing a weird behavior and I'm not sure if it's hardware or firmware related. Here I'm looking for some hints ...
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1answer
189 views

What is a “Phantom Clock” RTC, like the Maxim DS1315 and how is it different to “regular” RTCs?

I am looking for some RTC on the Maxim website and noticed a few rather expensive chips that are labeled as "NV SRAM with Phantom Clock" and there is a dedicated "Phantom Time Chip", the DS1315. The ...
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1answer
221 views

What to do to make the clock in the microwave always correct?

My new microwave has the same problem, after setting the correct time, after a week there is already 40 minutes forward. I even thought to install my RTC in it, but the manufacturer should somehow ...
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1answer
614 views

Reading onboard-RTC registers of STM32F411

I am trying to read the values in the seconds register of on board RTC of the STM32f411E discovery board. I want to transmit the values to my serial port. I believe i have initialized the hardware ...
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1answer
48 views

Real time clock loses SCL I2C signal when backup battery is added?

I have a real time clock module in my layout (same parts as this module from Sparkfun: https://www.sparkfun.com/products/12708 ), when I have my system set up WITHOUT the backup battery, I am able to ...
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2answers
4k views

STM32 RTC freeze when power is off

I am using an STM32F745VGT6 user board with Keil µVision 5. I want to use the internal RTC calendar with the internal clock (LSI). My question is: first power on clock start 02:00:00 then time is ...
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2answers
1k views

Why Cubemx use 0x32F2 as an indicator for the RTC configuration?

I've created a program with activated RTC peripheral by cubemx. After analyzing the code and searching in the internet, I found out that the reason of writing 0x32F2 in RTC_BKP_DR1 is for checking ...
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1answer
1k views

DS3231 on Battery Power and Use of Aging Register

Currently working with DS3231M RTC module with Arduino Uno and also creating a library for this. It is working perfectly but I have a doubt that DS3231M work on both VCC(main current) and VBAT (i.e ...
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2answers
82 views

Building a clock. Need some guidance

Alright so I learned all the fundamentals of the AVR and now I am thinking of building a clock as a project. I will use the ATMega328P along with the DS1307 RTC. The time will be shown on an LCD or ...
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1answer
499 views

RTC battery deep discharge protection

I'm doing an application using RTC on STM32F091. I'm using a small rechargable Li-Ion battery (such as MS920SE-FL27E) as the Vbat power source for the RTC. My concern is, how can I protect the ...
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180 views

Lithium button-cell battery discharging really quickly

I am working on a board with an ARM9 (SAM9X25). On this board there is a 3.3V lithium button-cell battery powering the VDDBU power rail. It is also used with a 100kOhm pull-up resistor for WKUP with a ...