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).

Filter by
Sorted by
Tagged with
1
vote
2answers
37 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 ...
1
vote
1answer
53 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 ...
1
vote
0answers
24 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 ...
1
vote
2answers
75 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 ...
1
vote
0answers
47 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 ...
2
votes
2answers
65 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 ...
0
votes
1answer
78 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 ...
-1
votes
1answer
57 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 ...
0
votes
2answers
139 views

Why do most microcontrollers not embed a 32k oscillator?

Why do most embedded systems use an external 32k oscillator?
0
votes
2answers
82 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 ...
2
votes
2answers
227 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 ...
1
vote
1answer
129 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 ...
1
vote
0answers
19 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 ...
0
votes
0answers
39 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 ...
1
vote
1answer
73 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....
0
votes
2answers
61 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 ...
0
votes
1answer
53 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 ...
0
votes
1answer
286 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. ...
1
vote
1answer
30 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 ...
0
votes
1answer
98 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 ...
1
vote
2answers
45 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 ...
0
votes
1answer
82 views

Real time clock coin cell battery charger in circuit

Firstly, I'm new here so don't be too harsh if I get something wrong, please just inform me of the right thing to do. I'm a second-year engineering student in New Zealand. I am using a DS3231 Real ...
0
votes
1answer
38 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" ...
1
vote
1answer
528 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. ...
0
votes
2answers
132 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 ...
1
vote
1answer
81 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 ...
4
votes
1answer
162 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?...
0
votes
1answer
63 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 ...
1
vote
1answer
327 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 ...
0
votes
1answer
44 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)...
0
votes
0answers
61 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 ...
0
votes
1answer
241 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 ...
0
votes
3answers
120 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 ...
2
votes
3answers
5k 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 ...
0
votes
2answers
625 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 ...
0
votes
0answers
395 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 ...
0
votes
1answer
176 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 ...
0
votes
0answers
161 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 ...
0
votes
0answers
96 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 ...
2
votes
3answers
330 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 ...
0
votes
2answers
511 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 ...
0
votes
2answers
109 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, ...
2
votes
1answer
1k 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 ...
0
votes
1answer
624 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 ...
11
votes
7answers
7k views

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 ...
2
votes
2answers
438 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 ...
3
votes
2answers
771 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 ...
5
votes
4answers
719 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-...
0
votes
1answer
4k 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 ...
0
votes
1answer
49 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?