Skip to main content

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
2 votes
1 answer
66 views

RTC Crystal severe timing issue

The issue is that my RTC 32.768KHz Crystal is oscillating at ~31.5kHz to 33kHz, depending on Load Capacitor values from troubleshooting. This was verified using the RTC_output signal used for ...
Kevin Lupercalia's user avatar
1 vote
1 answer
149 views

Supercapacitor discharging fast when there is no discharge path present

This question is a continuation of my previous question, but different from that. I am using a PCA85073A RTC in my design. On some boards, the supercapacitor discharges very fast (5 V to 1.1 V in half ...
Confused's user avatar
  • 2,583
0 votes
1 answer
76 views

What will happen if I2C pull up voltage became zero

This is a continuation of this question. In my board RTC I2C lines are pulled up to controller supply voltage and the controller supply voltage will be off when the system is off. At that time also ...
Confused's user avatar
  • 2,583
0 votes
1 answer
67 views

DS1307 RTC Time Drift

Do you Know, how much the tolerance of ds1307 RTC is per day? Most importantly, is this time tolerance a fix value or it has random error. Can we fix this problem with code? Edit: By the ...
Saeed's user avatar
  • 21
4 votes
1 answer
1k views

RTC super capacitor is discharging very fast

I am using a PCA85073A RTC in my design. On some boards, the supercapacitor discharges very fast (5V to 1.1V in half an hour.) This happens when we turn off 5V_uC. The circuit is given below. All the ...
Confused's user avatar
  • 2,583
2 votes
2 answers
83 views

Importance of load capacitance in 32.765 kHz crystals

I am designing a very low power portable device that has an RTC and I cannot choose a crystal for it. Most crystals on the market have 12.5pF load capacitance, however there are also 6 or 4pF crystals ...
Archimedes's user avatar
0 votes
0 answers
13 views

On the Epson RX8900 RTC, why when I start a fixed cycle timer the first cycle is too short by up to 1 second?

This is the signal diagram from the datasheet. The time period pointed to be the red arrow here is wrong. In fact, the fixed cycle timer uses the internal second (minute) register respectively to ...
bigjosh's user avatar
  • 10.2k
0 votes
0 answers
230 views

STM32 Wakes up from standby mode immediately

I'm trying to get my board (STM32L072CZ) to enter the standby sleep mode, and it seems to be entering this mode, but it also immediately wakes up again. After searching the great webs the solution ...
Rasmus Madsen's user avatar
0 votes
2 answers
167 views

STM32F407 interfacing with DS1307 RTC

The following code sets the initial state of the RTC sensor: ...
DaveFenner's user avatar
0 votes
2 answers
272 views

DS3231 ESP32 I2C problem?

I've got a new board prototype with an ESP32-S3 and a BME688 and and DS3231 on the same I2C bus (using pins 48=SDA and 47=SCL). I run the Examples => Wire => WireScan example making the ...
vicatcu's user avatar
  • 22.8k
0 votes
1 answer
170 views

STM32F103C8T6 BluePill - HAL_RTC_AlarmAEventCallback - Not call

I have a problem: I can’t get the alarm clock to work on the BluePill board. I need to get an interrupt to wake up the chip from Stop mode. It seems to me that the problem is in my BluePill board, ...
Vyacheslav Nizhegorodtsev's user avatar
2 votes
1 answer
4k views

Does the ESP32 WROOM-32 have an internal RTC?

I am working on an ESP32 WROOM-32 now. My purpose is to have it read some data every 15 minutes, in between the ESP32 goes to sleep mode. Does the ESP32 have an internal RTC or timer? I searched on ...
Kuralmozhi's user avatar
2 votes
1 answer
263 views

Is my circuit correct (Nixie Tube Clock)?

I am making a clock with Nixie tubes IN-12 A and made a circuit. I would like to know if it is correct before making the PCB and 3D case.
Eileen's user avatar
  • 23
0 votes
0 answers
164 views

Powering RTC DS3231 through BAT pin while keeping the coin cell battery in place

I'm working on a battery-powered DSLR camera controller with a MCU (ATMEGA328P) that spends most of the time in deep sleep and a RTC (DS3231) that wakes up the MCU a few times a day to take a picture. ...
Camilo Rada's user avatar
1 vote
2 answers
134 views

Can I read time data from an RTC (Real-Time Clock) chip without a microprocessor?

I have an HD146818 (Motorola MC146818) integrated circuit, which is a real-time clock. I would like to build a simple clock on it, which will control an 8-segment display. I read the datasheet for ...
Jerzy Przezdziecki's user avatar
1 vote
2 answers
518 views

STM32F746 Disco: Why doesn't the RTC generate an alarm A interrupt?

I'm trying to generate an interrupt every 60 seconds using alarm A. I put a HAL_GPIO_Toggle instruction inside the interrupt HAL_RTC_AlarmAEventCallback to turn an LED on to see if it triggers but I ...
Rodo's user avatar
  • 1,130
0 votes
0 answers
21 views

Seeking a equivlanet RTC for replacing a BQ4285S RTC

I'm going to start a project that requires a BQ4285S RTC. The problem is finding a BQ4285S (other than from questionable sources in China directly) or equivalent replacement since I don't know if any ...
cajoe's user avatar
  • 1
0 votes
0 answers
417 views

Read battery voltage for external RTC on STM32

I am using STM32F446RE for my application to just log the time accurately. I have an RTC module DS3231SN connected to the STM32 on the I2C. The RTC is connected to a coin cell battery CR2032 for a ...
dreamcoder's user avatar
0 votes
0 answers
155 views

Building an PTP TSU + RTC module

I want to build a simple Precision Time Protocol Timestamp Unit and Real-Time clock (PTP TSU + RTC module). My accuracy requirement is +-50ns. I found a good opencore ha1588 which fits for RTL part. ...
Ken Tsang's user avatar
1 vote
1 answer
102 views

How can I perform a slow shutdown on the power supply of an RTC after turning off the circuit?

I have designed a circuit that includes an RTC, the model is RV-3032-C7. We were able to configure it and the device performs its function, but I have a big problem. Occasionally, when I turn off and ...
WalterPH's user avatar
  • 440
0 votes
1 answer
183 views

Newly purchased DS1302 IC not working

I want to add a RTC in my own custom PCB using a DS1302 IC. I am using the Arduino IDE and an ESP32 controller. I made a PCB and tried to run it but it failed to read data from the RTC. Just to make ...
dharmikP's user avatar
  • 525
0 votes
1 answer
88 views

MSP430 RTC_B Back up Battery Supply

I plan on using MSP430F5636IPZ from Texas Instruments as my microcontroller in a project which I am currently working on. The MCU comes with a RTC_B (Real Time Clock) with Battery Backup capability. ...
solitude_surfer's user avatar
2 votes
3 answers
1k views

Is it a good idea to use the internal RTC of a microcontroller or is it better to use an external one?

I am designing a datalogger, and want to use an STM32L4R5VGT6 MCU. I know that this microcontroller has an internal RTC, so to avoid buying an external RTC I want to use the one that comes built into ...
WalterPH's user avatar
  • 440
0 votes
3 answers
158 views

DS3231 RTC interfacing with Raspberry Pi 3B

I want to interface a DS3231 RTC module with my Raspberry Pi 3b model in a project. As we all know this RTC module supports only I2C communication, where pin no. 3 and 5 of the Raspberry Pi are used ...
John Mist's user avatar
6 votes
4 answers
985 views

I'd like to request a review/bashing of this circuit for a high precision soil moisture sensing and analysis device. Where did I go wrong?

Below you will find a buffet of questions and the schematic for my device. (Click on it and you will get the full-size image.) Please tear this up. I'm a self-taught novice putting together a high-...
Tim Cerka's user avatar
  • 109
0 votes
1 answer
261 views

MCP7940 - power loss during time set

To set time in MCP7940 I should stop oscillator. If power loss will occur in this moment, RTC will not resume. Is there any way to overcome this problem ? Continues time is critical for my project.
Jarek's user avatar
  • 103
0 votes
1 answer
200 views

Regarding RTC drift

Basically there are two RTCs: 1.internal RTC 2.external RTC Internal RTC has no battery backup whereas external RTC has CR2032 battery to maintain time in absence of power supply. For accuracy ...
happy's user avatar
  • 11
1 vote
2 answers
2k views

Deep sleep wake ESP8266 with DS3231 RTC alarm

I'm trying to use a DS3231 RTC to wake my ESP8266 at a specific hour, minute and second. My circuit is a very low power design. I believe I need to reset my microcontroller (by momentarily pulling the ...
Nick Bolton's user avatar
  • 2,103
2 votes
1 answer
567 views

RTC_RD_TIME: Invalid Argument error [closed]

When I try to read hwclock date and time manually it is working fine. ...
Sukanya U's user avatar
0 votes
1 answer
82 views

RTC counter wrap mode

In the synopsis of the datasheet for RTC we have one feature i.e. counter wrap mode My understanding for this feature: RTC is 32-bit, i.e. \$\ 2^{32} = 4295947296\ \$ seconds counter will increment ...
Sukanya U's user avatar
0 votes
1 answer
107 views

Can RTC IC detect power cut situation?

I have been making research about power down detection on Google. The only battery powered IC in my circuit is PCF85063 RTC IC. Here @VoltageSpike says that it is possible with using RTC IC and ...
Bowman's user avatar
  • 349
1 vote
1 answer
273 views

Can't access RTC Alarm Registers for second time

Hi STM32F103 Programmers I am fighting with my RTC. I have it working but have problems with accessing the Alarm registers for the second time. I can't find the reason why I can't. I program the RTC ...
wogoos's user avatar
  • 71
0 votes
1 answer
292 views

PC: Which crystal is used for main clock? (X570)

I want to improve intrinsic (hardware) precision of windows/linux (OS) time (specifically, in my case it's AMD X570 platform), without relying on periodic correction via NTP servers. Common approach ...
BarsMonster's user avatar
  • 3,219
2 votes
1 answer
151 views

Why is the time lagging behind on the Renesas ISL1208 real time clock (RTC) in battery mode?

For a project I am using the ST M41T81 RTC but because of the parts shortage, I updated the firmware to support both the M41T81 and LS1208 RTC chips. The reason I am using the LS1208 is because the ...
ChassakAPT's user avatar
2 votes
1 answer
1k views

RTC on STM32 doesn't start running, except when a breakpoint is active

I use: STM32L071K8U3 Segger JLink + Segger Ozone + SWD with 4 MHz Cube Ide External LSE or internal LSE, same problem. I wrote firmware that displays the time using the RTC. To update the display, I ...
Oliver Richter's user avatar
2 votes
1 answer
64 views

Identify component RTC 10800

I’m a little stuck on this component, it’s on the incoming 230 V supply line to a battery charger circuit, so it should be a surge thermistor, but I can only find types of NTC or PTC, not an RTC. Any ...
redpegleg's user avatar
0 votes
2 answers
1k views

External load capacitors on 32.768 kHz crystal oscillators

I am trying to design a circuit with the MCP79402 RTC. However, I do not understand why the crystal oscillators require external capacitors, and I am confused on how to calculate values for said ...
Bradley Campbell's user avatar
-2 votes
1 answer
34 views

Combined timer/RTCC [closed]

I have been using a Maxim DS3231 as a RTCC with its alarms used to "wake up" certain hardware. Now I need to wake up the hardware periodically, say every hour, so I actually need a timer (...
Guille's user avatar
  • 101
6 votes
2 answers
1k views

Symbol identification (J?)

I am looking into a part from a application guide titled How to Calculate UNIX ® Time Using a PIC18 Microcontroller and the MCP795W20 SPI RTCC. And there is a part that I'm not sure what it's suppose ...
HFOrangefish's user avatar
0 votes
2 answers
1k views

Do I need RTC while I'm using NTP?

We know computer and another device like microcontroller is not accurate in ticking clock comparing to wall clock that using cesium atom. I heard RTC module is purpose to making accurate the ticking. ...
Muhammad Ikhwan Perwira's user avatar
1 vote
1 answer
173 views

RISC-V GD32VF103 battery backup domain

I'm not sure how the VBAT pin of the GD32VF103 RISC-V MCU should be connected, exactly. The GD32VF103 User Manual states: The Backup domain is powered by the VDD or the battery power source (VBAT) ...
maxschlepzig's user avatar
4 votes
1 answer
593 views

Can a memory backup supercap hold on for more than 2 weeks?

Most RTC chips have a VBATT input for backup power supply; besides a battery, you can use a supercap there, e.g. using the following scheme: simulate this circuit – Schematic created using ...
anrieff's user avatar
  • 5,469
0 votes
0 answers
37 views

Are There Any Standards for RTCs, Similar to JC42 Temp Sensors?

When I place a temperature sensor on a board, I like to use a JC42-compliant temperature sensor. I know of at least half a dozen manufacturers that build these temperature sensors in exactly the same ...
MyDirtIsRed's user avatar
0 votes
0 answers
181 views

LiPo cell as RTC backup battery

I am wondering what is the sensible way of using the LiPo cell that powers a handheld device to also act as the RTC backup battery for the MCU. There is charging circuitry for the LiPo cell on-board ...
Hamza's user avatar
  • 136
-1 votes
3 answers
134 views

Simple circuit to sample 120 VAC and yield 8.33 ms pulses

Have you noticed the lack of availability and prices of RTC chips lately? A simple DS1307 RTC is simply not available right now. Last year I purchased DS1307s for less than a buck. Now they are $4+ ...
Doug12745's user avatar
  • 319
0 votes
0 answers
41 views

DS3231SN RTC -- timing between 1Hz SQW and clock seconds?

I don't think this is addressed in the DS3231SN datasheet but I may be missing something. When the SQW output is programmed to output a 1Hz signal, is there a known / fixed phase relationship between ...
Jim Mack's user avatar
  • 213
0 votes
0 answers
123 views

I2C bus slave powered before raspberry pi master

I have a number of I2C slaves (PCF85063AT) connected a Raspberry Pi, which acts as master. For various reasons the I2C slaves are powered at all times, where the power to the Pi can be controlled on/...
stackman82's user avatar
0 votes
0 answers
91 views

I2C via MCU works with FLAG_WRITE_READ but not FLAG_READ

I'm reading the date from an RTC via I2C using a SiLabs MCU. There are two different flag options, but only the 2nd one works. I'm new to implementing I2C, what is happening on the wire that works ...
KJ7LNW's user avatar
  • 2,000
0 votes
1 answer
158 views

Converting code with Boolean to a byte array

I am having a hard time understanding this code. I have code I am working on to sequentially flash the current 12 hr time on a single 7-seg display when you press a button. I used a Boolean matrix to ...
Austin Fox's user avatar
1 vote
1 answer
138 views

DS3231 Question

Can someone help me understand the differences between: "Adafruit DS3231 Precision RTC Breakout" and one of these generic breakout modules, "DS3231 AT24C32 IIC RTC Module"? Why I ...
Austin Fox's user avatar

1
2 3 4 5 6