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 does buffering in the MCP79410 RTC work?

From the MCP79410 datasheet, p.16: Doesn't this mean that the data is being buffered when I read the seconds register, then again when I read the minutes register, and so on? This would mean ...
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1answer
45 views

Interface RTC and Accelerometer to Arduino UNO board [closed]

We are trying to interface RTC DS1307 & ACCELEROMETER ADXL345 on arduino UNO board. Both these requires analog pin A4 and A5 of arduino but at a time we are able to connect only one of the deive, ...
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2answers
119 views

Why does my RTC generate interrupts faster than once per second?

I have configured an RTC module on a uC to generate interrupts every second (~32 kHz module clock with a 0x7FFF prescaler in between the counter and the clock - I hope so, seems like ~32k is the ...
2
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1answer
57 views

SIM900 CR2032 rtc battery backup

I would like to use a CR2032 battery to power the internal RTC of the SIM900 gsm module. The datasheet (given in the link) says that the battery should be rated at 3V. They also give the following ...
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3answers
77 views

Issue with performing I2C read operation from ds1307 to pic18F

As advised by my fellow stackers in my previous post, I tested the "Write_to_slave" function in Proteus as well in real time, by sending bytes to the RTC and the slave is responding appropriately with ...
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2answers
68 views

RTC_DS1307 + PIC18F458 displaying time and date as zeroes

I am trying to get the RTCDS1307 + PIC hardware to work in order to display the appropriate data and time. But the problem is that, its displaying the time and date as 00:00:00 and 00/00/2000 as ...
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1answer
149 views

Abracon RTCC - no startup oscillation, no SPI

I'm trying an Abracon AB1815 Real-Time Clock/Calendar (SPI interface) in a "fun" QFN16 package. It has a 17th VSS pad which is grounded. It is on a QFN17-to-DIP expander for prototyping at 1.8v. I ...
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1answer
96 views

Is there any way to calculate milliseconds from DS1307

I have a DS1307 and I have done its program and taking out time from it. In my program I have sec1,sec2 which holds the digits of seconds and same for ...
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2answers
97 views

Where to save DS1307 program to get real time value?

I am integrating DS1307 in my project and using PIC32MX795F512L MCU. I have somehow managed to do I2C communication in it and ...
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1answer
42 views

What is the purpose of SRAM in the DS1307 RTC chip and the onboard AT24C32N EEPROM chip??

I am going to interface a RTC to PIC18F and before doing so, I'd like to clear some doubts regarding the module and its connections. I am using the "Tiny RTC" as shown in this link!. The following ...
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1answer
38 views

Few queries on how to set real time clock value in DS1307

I need to integrate DS1307 RTC in my project. I have somehow managed to write I2C code and interfaced it with PIC32. I need to make a logic so that it shows real ...
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1answer
51 views

PIC16 LP drive level - do I need a damping resistor?

I'm using a 32kHz crystal oscillator with timer1 on a PIC16F1825 to provide more accurate timing for events (I want to do something every 20 minutes). The crystal circuit looks easy enough to design ...
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1answer
178 views

Can I replace watch quartz with DS3231 32 kHz output?

I'd like to know if it's possible to synchronize classical quartz clock by replacing inbuilt quartz crystal with DS3231's 32 kHz output. I need to synchronize my analog watch with RTC DS3231. Am I ...
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1answer
115 views

Error communication in I2C in PIC32 [duplicate]

Duplicate question was also asked by me and the current question has different code I have a PIC32 starter kit and I am making ...
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0answers
102 views

Transformerless Realtime Clock Issue

I have an issue with designing a Real Time Clock by using Transformerless power supply. I don't use RTC IC but I use Microchip PIC instead and 32kHz clock. I use battery of 3.3V for backup supply. ...
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1answer
134 views

Drive relay with Npn transistor thanks to RTC and Rpi

It' s my first projet in electrical and i m not very sure about what i'm doing ... I Would like to drive a relay thanks to a Rpi and a RTC clock that has a alarm feature ( ds3231 with high-z/active ...
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4answers
2k views

How often should I query a RTC?

I've not yet used a RTC so I'm not completely sure of the "normal" way to read a real time clock. There's a few different approaches I've thought of but was hoping for some advice on it. Here are the ...
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2answers
232 views

Can I use the 32.768 kHz output from a RTC instead of an external oscillator on a PIC MCU?

Using the 28 pin PIC18(L)F2X/4XK22 and a DS3231S real time clock. The MCU has input and output pins for an external secondary oscillator and the original schematic has no RTC, but an oscillator ...
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1answer
56 views

info for RTC module needed

I have this RTC module by MikroElektronika: I need a schematic and/or user manual but it's no longer on the MikroElektronika website. (There's a similarly looking PCB but it uses a different IC ...
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2answers
333 views

Help driving 9V circuit with a 5V RTC clock interrupt pin (active low)

I am using this RTC clock module (http://datasheets.maximintegrated.com/en/ds/DS3231.pdf). The DS3231 has alarm function that can be programmed twice a day. When the alarm goes off it makes the ...
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1answer
247 views

DS1307 not counting

I've got a TinyRTC board with a DS1307 on it connected to an Arduino. Setting the time and reading is no problem (using the DS1037 Arduino lib). Weird thing though is that when I disconnect the power ...
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2answers
228 views

function of RTC

I want to know about the real time clocks or RTC. What are the function of RTC IC. Each IC has I2C interface. What it is transferring through the I2C interface. Its really hard to understand the exact ...
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2answers
56 views

DS 1307 power issue

My DS1307 stops functioning when switching the relays. It looks like a power fluctuation problem. I added 4.7uf capacitor in parallel with the power source too. Before adding 4.7uf cap DS1307 stopped ...
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2answers
412 views

DS3231 Module Circuit Teardown

I recently purchased a DS3231 RTC module to use in one of my prototypes. Now that it is complete I would like to integrate the RTC directly into my PCB instead of using a plug in module. To that ...
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2answers
56 views

STMicro library for setting RTC Alarm on Sunday is incorrect?

I'm using a stm32fxx ARM Cortex-M3. When setting an RTC alarm for Sunday, I realized that the stm32l1xx_rtc.h header file defined Sunday as: ...
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1answer
148 views

What are similarities between RTC DS1374 and RTC DS1307

I mostly work in software and not good in reading Hardware data sheets. I need help in understanding the similarities between RTC DS1374 and RTC DS1307,From below link I could make out that both ...
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1answer
592 views

Supercap for Backup Power (10 hours Backup Time Min.)

I am using atxmega8e5 in a design and also utilizing its Real-Time Counter to act as a Real-Time Clock. A lot of RT-Clock ICs can use a SuperCap to have backup power incase the device is unplugged or ...
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0answers
413 views

RTC DS1307 3.3V I2C and Oscilloscope impedance

I'm working on a library for STM32 to learn I2C protocol (Software I2C, not hardware). I connect my DS1307 (Sparkfun BOB-12708) : (Here is the module schematic) : I remove welding on the SJ2 jumper ...
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0answers
995 views

STM32F030 RTC wakeup from stop mode

I'm writing an app, that most of its time will spend in STOP or STANDBY mode (battery powered microsystem). I'd like the internal RTC to wakeup my STM32 every 5 minutes, enter the ISR, do its tasks in ...
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1answer
113 views

DS1302 realtime clock - pulldowns required?

I'm trying to wire up a DS1302 realtime clock, one of these: to a parallax propeller board. The datasheet says (page 4) that pulldowns are integrated into each of the main lines (looks like 3 ...
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3answers
757 views

How to turn on ATmega every 6 hours?

The board which is made with Atmega operates on battery, it should turn on every 6 hours and log some data, then go back to deep sleep to save battery consumption. Atmega32 is used and not Atiny ...
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2answers
2k views

STM32 RTC alarm not configuring for the second time

I am using STM32l151vbt6 MCU and I am trying to configure RTC Alarm for every 15th minute. (That is 0, 15, 30 and 45th minute of the every hour.) I can configure the alarm and it will work for the ...
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5answers
646 views

How is time of supplied real time clock module maintained without battery?

I am thinking about purchasing this RTC ( real time clock ) module. Since this particular item comes supplied without a battery, I wonder how the time is being kept running in the chip since it's ...
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2answers
350 views

Arduino I2C and multiple devices

I have created two projects, one with a Tiny RTC and another one with the BM180 sensor to read barometric pressure and temperature. Now I want to combine both. I'm trying to connect both - the ...
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1answer
530 views

If I'm using an RTC and ATMega328p (arduino UNO chip), do I need two crystals?

If I'm using an RTC that requires an external crystal, do I need a second external crystal for my ATMega328p? Or can the two share? What is standard practice for this kind of thing? I'm making a ...
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2answers
315 views

Periodic timer (64Hz) with ARM processor and (embedded) Linux

I want to call a function 64 times per second with a ARM processor which is running linux. (ex: Rasberry Pi or Freescale i.mx6). Ideally, I don't want too much jitter. I want to perform a task ...
2
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1answer
1k views

Problem using DS1337 - RTC

I am trying to use a edited version of the library given at this link. I basically changed some of the included file and some of the changed function of the wire.h library. Though I am not a hardcore ...
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1answer
61 views

I2C access on M41T00CAP RTC device

I am trying to access "M41T00CAP RTC" device through I2C. there are other I2C devices also, which I am able to access perfectly. but in case of RTC device , I am not able to read the register ...
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7answers
17k views

What happens if I omit the pullup resistors on I2C lines?

Just now I realized that the I2C data and clock lines (SDA and SCL) must have pullup resistors. Well, I've built a couple of clocks using the DS1307 RTC (see datasheet) according to the schematic ...
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2answers
117 views

Synchronize RTC of 2 different MCU's [closed]

I have 2 different microcontrollers and I need to use their internal RTC. however I need the 2 RTC's to be in sync when they are used. How would I achieve something like this?
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1answer
785 views

Switching Arduino/ATMega to sleep mode when on battery

I'm trying to make a small clock but want to ditch the need for a separate RTC chip with battery backup. What I would like to do, instead, is keep track of the time completely on the ATMega using the ...
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1answer
327 views

Designing a large 7-Segment display

I'm trying to design a product that have the following features for mass production, and I'm asking from your experience, how to get the lowest price for the components, quality of the chips in terms ...
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3answers
6k views

How to modify DS1307 RTC to use 3.3V for Raspberry Pi?

I bought DS1307 RTC but it is 5V so it can't be connected to the Pi. I know it can be modified to use 3.3V by removing 2 resistors. This sensor is different than the adafruit kit so I am not sure ...
2
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1answer
1k views

Real Time Clock DS1307 interfacing with Arduino Uno

I am currently working on an electronics project of building my own Digital wall clock. For that I tried making a RTC module with DS1307 IC. I followed the following instruction from this website. ...
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2answers
251 views

What is the purpose of the capacitor in this schematics?

I am trying to understand a RTC module from Sparkfun. I don't understand the purpose of the capacitor in this circuit. Here are the procduct's page and the schematics link. Can some one please ...
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1answer
458 views

Sanity check: Using the DS3231 as a clock source for uC

The DS3231 is an RTC chip with an onboard temperature compensated oscillator and 32kHz output. I want to use this chip in a small clock project I'm designing because I've got a couple lying around. ...
3
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1answer
249 views

Working with a BQ4285 RTC from Texas Instruments

I recently acquired a BQ4285 Real-Time Clock manufactured by Texas Instruments... And I have one major problem! I have little idea how to use it. I am trying to connect it to an Arduino Mega 2560, ...
5
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1answer
3k views

How long will a DS1307 RTC run on a CR2032 coin cell battery?

I have a homemade clock based on an atmega328 and a DS1307 Real Time Clock. When off, the DS1307 is powered by a 3V CR2032 coin cell, as usual. If I leave the clock off most of the time, how long ...
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2answers
390 views

Could these ICs from Alibaba be counterfeit?

I'm trying to source some parts for a kit and the most expensive part I have by far is the DS1307+ RTC chip. They run about $4 in single buys and $1.96 in larger quantity. But then there's this: ...
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1answer
429 views

How to improve I2C RTC accuracy

I´m using a PCF 8583 I2C RTC for one of my projects (i´m not a professional, just an amateur). The clock delays about an hour per day, which I find unacceptable. I´m using a 32768 Hz, 12.5 pf, 50 ...