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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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
46 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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0answers
17 views

Two different write lock disable methods for the PIC24F RTCC module

In my previous question I used the write unlock mentioned in the the application note, now I used the sequence mentioned in the datasheet: ...
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1answer
52 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 ...
4
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2answers
200 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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0answers
148 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 ...
2
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5answers
235 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
78 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
124 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 ...
3
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2answers
112 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
281 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 ...
0
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1answer
38 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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6answers
3k 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
71 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
267 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
256 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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1answer
1k 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
519 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. ...
2
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2answers
196 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 ...
3
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1answer
189 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. ...
2
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1answer
146 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, ...
2
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1answer
843 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 ...
3
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2answers
234 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: ...
5
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1answer
275 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 ...
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1answer
294 views

PIC : problem with initialize internal RTC of PIC18F67k22.

I want to initialize internal RTC of PIC18F67K22 with some fix time&date.Time is set properly but date is not set properly.problem occur in setting year.year is not set to whatever we give to ...
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3answers
710 views

Turn on arduino with RTC Alarm

I would like to have a RTC alarm turn on my arduino at a specified time each day. I know that Arduino has good sleep modes but I'm concerned even with the quiescent power consumption from the voltage ...
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1answer
114 views

How do I configure a external RTC that uses 3-wire SPI for the LPC 2387?

Here is the link to the datasheet of the RTC PT7C4302. I can do it with MISO, MOSI, but SISO I have no idea how to do. Some similar code examples would be great.
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1answer
1k views

RTC on MSP430 microcontroller with 32.768kHz crystal and low power

I need to set timer to interrupt every second. I'm using 32.768kHz external crystal with MSP430G2553 MCU. The setup should consume < 10μA. I tried this code but it consumed 80-90 μA. What am I ...
2
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2answers
469 views

Does polling a DS1307 too frequently affect accuracy?

I did some research, and I found contradictory response on the web. I'm polling a DS1307 on an loop, with an Arduino, that takes about 20 ms to run, so basically I'm polling the I2C interface 50 times ...
0
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1answer
386 views

ds1307 drift too big

I have a RTC ds1307 mounted on a prototype board ( the one with 3 pin stripped ), and I'm experiencing a delay of about 5 sec/day, far too big compared to some research I did. Can that delay be caused ...
6
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3answers
910 views

How to calculate day of the week for RTC?

I am using MCP7940 RTC from microchip it requires to enter the day of the week as part of updating RTC with date. So how should I calculate day of the week based on the date provided by the user ?
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2answers
257 views

How to Synchronize two RTC module one internal and other external?

I am developing a data logger based on PIC controller. The PIC has internal RTC but does not have pins for connecting battery so I am using pic's internal RTC to generate interrupt every second and ...
1
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1answer
336 views

I2C with DS1307 hang after end of transmission

I've got a home brewed RTC with DS1307. I've put two pullup resistors on SDA and SCL lines, connected them to the Arduino 5 and 6 pin respectively. I've also provided a backup battery since I read ...
0
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1answer
889 views

Is there any Real time clock (RTC) which provides time resolution in microseconds?

I've been searching for high precision RTCs on Google but almost all RTCs like DS12C887, DS1307 provide time resolution in seconds which is ok for general use. But is there any RTC IC which can ...
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2answers
495 views

DS1307 RTC not working with rweather library

I'm using the DS1307 RTC together with arduino and this library http://rweather.github.com/arduinolibs/classDS1307RTC.html When i power the chip directly from the 5V and GND outputs from my arduino ...
1
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1answer
151 views

Using alarms with the DS1307RTC

I'm trying to wrap my head around following library: http://rweather.github.com/arduinolibs/classDS1307RTC.html I can see that the DS1307RTC has a writeAlarm and readAlarm function. I'm not sure how ...
5
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3answers
424 views

DS1307-breakout-board

I want to build an RTC clock for the Raspberry Pi. Adafruit has a guide to accomplish this with Dallas DS1307. On the schematic they put a 2.2K resistor between VCC and SCL and do the same for VCC and ...
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3answers
1k views

Two wire vs. three wire serial interface for RTC

I'm looking to choose an RTC for a project I have in mind. I have the following options (linked to datasheet): DS1307 DS1302 The main difference seems to be the communication protocol. The DS1307 ...
1
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1answer
134 views

DS3232M Skips seconds when writing to SRAM

I'm using a DS3232M that works great for keeping track of the time until I try to write to the SRAM on the chip. When I use the SRAM it slows the updates of the seconds register or stops them all ...
1
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1answer
485 views

Multiple masters for i2c device

I have a DS1307 RTC chip that I want to interface with multiple masters. One, an ATMega chip, will only ever really need to pull time data from the chip and the other (probably just an ATTiny) will ...
5
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2answers
521 views

How does GPS calculate time

How can a GPS device give exact timing even when the number of available satellites are zero? I'm monitoring GPS data using VisualGPS.
5
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4answers
2k views

DS1307 power failure problem

The DS1307 has two power sources: the main VCC source and the backup battery. The latter will power the DS1307 when the main power goes down so the clock can keep ticking. I am facing a problem with ...
1
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1answer
514 views

RTC on a circuit board and little green disk 00504 [closed]

I have a 110 volt powered mini fridge. after replacing a board soldered fuse with a replaceable set up I have discoverd a component that looks similar to a capacitor disk that is cracked. the fuses ...
1
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2answers
241 views

Ground copper pour for Crystals and Real time clocks

I am laying out a (2-layer) board, with a standard SMD Crystal as well as a Real-time clock placed on the top-side of the board. What are guidelines regarding ground copper pour under the Crystal and ...
3
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2answers
967 views

Is case grounding compulsory in typical 32.768kHz crystal for Real Time Clock?

Pictures shown below is a typical 32.768kHz crystal, commonly use in Real Time Clock circuit (e.g: DS1307 & DS1337) Referring to an earlier question posted here, it is a good practice that ...
2
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2answers
245 views

Device including RTC EEPROM and battery?

I am currently designing an electronic board and i got a question: Do you know if there is any device in which are integrated an RTC, an EEPROM and a battery? I heard about this type of device (i ...
9
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3answers
2k views

How do you Calibrate 32.768kHz crystal for PIC24 RTCC

I'm trying to figure out the best method for PIC24 RTCC crystal calibration. Their application note states two methods: using a lookup table and using a reference system clock. According to them the ...
3
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4answers
320 views

RTC clock skipping months back

I will come to a question further down, but first a little background We are struggling with reproducing a nasty bug that we have been getting reports for. The symptoms clearly show that the RTC (a ...
7
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2answers
1k views

supercap-powered RTC?

I'm designing a ATmega-based microcontroller test board. One of the features I want to include is a Real Time Clock with a Maxim DS1307 IC. Instead of including a traditional coin cell battery backup, ...
4
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1answer
160 views

How to sync sensor data

Suppose I have multiple dataloggers receiving sensor data, how can I sync those signals afterwards? The most obvious way would be adding timestamps to the data, but they have independant clocks, so I ...