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Questions tagged [rtc]

a Real time Clock, a computer clock.

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Scheduling Questions with Pi 5 rtc and /sys/class/rtc/rtc0/wakealarm

So the new Pi has a built in RTC and for $5 I can attach a rechargeable battery that lets the RTC tick on even when the power is cut. This is great because I want to emulate the wake up behavior of an ...
blorgggg's user avatar
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1 answer
846 views

What kind of JST connectors are needed for the Raspberry Pi 5?

All of the documentation I can find for the new JST headers on the Raspberry Pi 5 fails to mention which series of JST connectors it uses. If I want to make up my own 4-pin PWM fan, 3-pin UART or 2-...
Mark Booth's user avatar
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0 votes
4 answers
115 views

Run systemd timer periodically but not on boot

I would like to run a script every 30 minutes on my RbPi, but not immediately after boot. Example: If I boot my RbPi at 15:15, the script should run at 15:30 not before. Setup: My RbPi has no ...
Pa Dalton's user avatar
0 votes
0 answers
66 views

Raspberry Pi 4 - hwclock DS3231 RTC delay at boot

Running a Raspberry Pi 4 with a DS3231 RTC setup. Everything is setup correctly and working fine and the hwclock is synced correctly. The unit is running without any internet connection. The problem ...
William's user avatar
0 votes
0 answers
73 views

How to use two different RTC modules (ds1307/ds3231) on the same PI

The question is: How to use the same SD image when you don't know which RTC module will be connected on top of Raspberry PI? I have two modules in use in config.txt: dtparam=i2c_vc=on dtoverlay=i2c-...
Dmitry's user avatar
  • 101
2 votes
1 answer
704 views

RPi4 Bullseye Cannot retain rtc-ds3231 hwclock value when internet is OFF

I followed all instructions from Adafruit website but the system clock is still not set after I turn off the internet. **The clock resets to 2000-01-01 00:00:00 when I turn off internet, shutdown, ...
curiousIya's user avatar
3 votes
2 answers
624 views

i2c Real Time Clock IC on Raspberry

I am using an industrial device based on a Compute Module Raspberry Pi 3 called Kunbus RevPi Core 3+. The device is shipped with Raspbian and a pre compiled Image but I would like to install an ...
Stefano Bossi's user avatar
1 vote
1 answer
218 views

Issue in RTC DS1307 delay when powering off Raspberry PI 4

I am interfacing a Raspberry PI4 with RTC DS1307 IC. The conditions that I checked are mentioned below: First install i2c-detect library in Pi4 and check whether my RTC interfaces properly or not ...
Dheeraj SmartIam's user avatar
0 votes
0 answers
986 views

How to give the on-chip RTC a power backup in Raspberry Pi Pico?

I need a power backup for the on-chip RTC on the Raspberry Pi Pico, like a button cell which is quite common. Someone suggested placing a 1.5V button cell between the VSYS pin and the ground. Would ...
Yatharth's user avatar
0 votes
1 answer
169 views

HAT EEPROM DTB and RTC on I2C0

I'm having a problem creating a DTB for a HAT auto-configuration. I have a DS3231 RTC module attached on I2C0 (GPIO0 and GPIO1). It incorporates an AT24C32 EEPROM at address 0x50. To get it working, ...
Bryan Horna's user avatar
0 votes
1 answer
555 views

RTC on Raspberry Pi Bullseye shows correct time but is not registered at boot time

I am testing different RTC modules on RPi 4 running on Bullseye. On testing DS3231, I add the module to /boot/config.txt dtoverlay=i2c-rtc,ds3231 I can read the clock from it wihtout a problem. But ...
forumflaneur's user avatar
-1 votes
1 answer
665 views

How to Use RTC Module (DS1302) to specifically Execute a Program at a Certain Time

I had already completed a Setup of DS1302 on my Raspberry Pi 3B+ and fortunately its working just fine. I also already solved the Problem of Turning On and Off the USB Port using "uhubctl". ...
Little Intoxicated's user avatar
2 votes
2 answers
2k views

Turn on pi at specific time with RTC to save battery

I'm looking into powering my raspberry pi via a powerbank. I already have a button and a relay to turn it on manually and when the pi shuts down flip the relay back to off position. Now I would like ...
Qorzyking's user avatar
0 votes
1 answer
438 views

RTC chip mcp7941x not working with dtoverlay i2c-rtc-gpio

I have an mcp79310 RTC chip installed on gpio pins 22 & 23, and I am attempting to use it with dtoverlay=i2c-rtc-gpio,mcp7941x,i2c_gpio_sda=22,i2c_gpio_scl=23 in /boot/config.txt and adding rtc-...
Scott's user avatar
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1 answer
165 views

Battery supplied e-ink photo frame with scheduled wakeup time

I am building a raspberrypi zero eink photoframe. My aim is to create a photo frame that I would be able to put on the wall without cables hanging around, battery powered. In order to achieve this I ...
VDC's user avatar
  • 109
0 votes
1 answer
246 views

why does my Pi clock survive a reboot without an RTC or internet?

It seems time on my RPi 3B v1.2 survives a reboot without either an RTC or an internet connection. I was given the Pi used by someone else, but I'm pretty sure I don't see an RTC connected to it. [![...
rbgorbet's user avatar
3 votes
1 answer
1k views

Is there a package or library for controlling the DS3231 on the Raspberry Pi

I've just obtained a DS3231 real time clock (RTC), and added it to my RPi 3b. It seems to work as far as keeping time, but I wanted more. I'd like to be able to set alarms to trigger the INT/SQW pin ...
user avatar
1 vote
2 answers
952 views

How to make sure RTC is accurate

I am using a RTC. I read the documentation for this module that it will lose a second every 24 hours. So, I assume i have to update it myself. After Googling I was drawn to this solution: hwclock --...
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1 vote
0 answers
37 views

Connect RTC while TFT Display is attached via gpio

I have an raspi zero and it is connected with a RB TFT 3,2" Touchscreen (I dont use the Touch function). Is it possible that I connect a rtc even if gpio 1 to 26 is already used by the screen? ...
VRK's user avatar
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1 vote
1 answer
1k views

Raspberry Pi 4 64-bit with RTC (Hardware Clock DS3231) Daylight Saving Time without Internet?

I am using a hardware clock to set the time on my RPI4. It does not use the internet. The timezone on the PI is set to Europe/Berlin. The HW Clock runs on UTC. So when day light saving time occurs, ...
zer02's user avatar
  • 113
0 votes
1 answer
464 views

Rasclock with Raspbian Buster not working

the rasclock is detected by the raspberry Pi but if I want to read or set the time on it I got the error hwclock: ioctl(RTC_RD_TIME) to /dev/rtc0 to read the time failed: Remote I/O error dmesg ...
Bierly's user avatar
  • 73
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0 answers
516 views

i2cdetect detects the device but also shows a full row of addresses

I have successfully setup a RTC clock ( DS3231 ) on a RPi zero. The whole process was explained here. It works as expected but with only a minor difference: Row 5 is filled with numbers from 0x50 to ...
BHP's user avatar
  • 101
2 votes
3 answers
7k views

How to check if installed RTC is working or not?

I have put RTC (Model is SHIM RTC Realtime Clock Accessory Board) at my RPI. I need to test if it is working or not. Is there any command which is checking if it is working or not? I am using RPI ...
Jakov's user avatar
  • 173
1 vote
1 answer
1k views

Load and unload hwclock (RTC) at boot. Can't get device to unload

On a Raspberry Pi 3 B+ I'm trying to read from a DS3231 RTC at boot time, sync the time to the system time and then unload the device. All the commands function from the terminal so I thought it would ...
AntonyCD's user avatar
0 votes
1 answer
364 views

DS3231 doesn't update its internal time?

UPD: with another chip of the same model RTC works just fine, presumably that the chip was broken/damaged. I installed DS3231 RTC clock ( which is detected as DS1307 for some reason). My config.txt ...
jdevelop's user avatar
  • 113
1 vote
0 answers
639 views

Using the MCP7940N RTC with the Pi 3B+

I have a breakout board with the MCP7940N RTC on the Pi 3B+. How do I get this to work. I've been following this guide but don't seem to be getting anywhere. In my /boot/config.txt I have added ...
electrophile's user avatar
0 votes
2 answers
855 views

What is the most apt way to setup a RTC?

I've gone through a plethora of sources and found it a little confusing with too much information hence posting this question. Firstly, the scenario is, I've set up my PI-3B(jessie) with PCF8523t RTC....
Manoj's user avatar
  • 11
2 votes
1 answer
1k views

WittyPi on Pi Zero W - I2C read / write fail

I've connected WittyPi2 (an RTC Power Management hat) to my Pi Zero W - but I'm constantly getting failures in the log, to do with the I2C communication: I2C read 0x01 0x68 0x09 failed (result=), and ...
Liam's user avatar
  • 21
3 votes
1 answer
397 views

Using RTC on Raspberry Pi Zero while SDA/SCL pins are occupied

I have a portable project on my Raspberry Pi Zero and I am using a i2c 0.96" OLED on the SDA/SCL pins on my Raspberry Pi. I would like to add a RTC Module to my project, but all of the tutorials I ...
chill389cc's user avatar
0 votes
2 answers
383 views

Why is my RTC DS3231 but seems DS1307?

I bought a RTC DS3231 because of the accuraty of time (2ppm, I was searching an accurate RTC). When I received it, I checked that in the encapsulating it is as well marked like DS3231. But, after ...
user940969's user avatar
0 votes
2 answers
455 views

Will adding RTC to a Pi make it more stable? [closed]

I use my Pi 3 as a desktop machine and it generally does pretty good. Occasionally I run into the issue that if I use an application, mainly Firefox and sometimes Chromium, the application will either ...
lockheed silverman's user avatar
2 votes
2 answers
491 views

What is the memory in the DS3232 RTC for?

I'm looking for an RTC to use with my Pi and came across the Maxim DS3231M. I also saw a similar model on Maxim's website, the DS3232M, which comes with 236 bytes of SRAM. The DS3231 seems to be a ...
zaen's user avatar
  • 123
0 votes
1 answer
1k views

I2C device (DS3231 RTC) not detected

I have a small DS3231 RTC module, like the following, that I am trying to get to work with my PI 3 Model B. However it is not correctly being detected by the Pi. Connected like so (ignore cables, ...
Jacob's user avatar
  • 101
0 votes
1 answer
337 views

Periodically update DS3231 RTC with NTP

I am working on a pi hat that will cut the Pi's power in the evening when the pi isn't being used in my application. Anyways, I have a couple questions about using the DS3231 RTC. There is a uC in ...
nichollsg's user avatar
  • 153
0 votes
1 answer
4k views

Sync time for all Raspberry Pi's on local network without internet

There are 5 Raspberry Pi's connected to one switch (No Internet) using LAN cables. One of the Raspberry Pi has RTC module connected and it has correct date and time. Now how can all remaining four RPi'...
Sundeep Kumar Gorantla's user avatar
1 vote
1 answer
711 views

Kernel does not use RTC

I have a PiFace RTC clock that I have setup on archlinux ARM on a rpi2. I have edited /boot/config.txt to add dtparam=i2c=on dtoverlay=i2c-rtc,mcp7941x=0x6f I have added i2c-dev and i2c:mcp7941x ...
solsTiCe's user avatar
  • 147
1 vote
0 answers
136 views

Kernel panic, real time clock (possibly), UPS Pico

Have a fresh install of KivyPie, which is some months old, with updates (have done apt update/upgrade). It crashes: and the reason seems to be these two lines enable_uart=1 dtoverlay=i2c-rtc,ds1307 ...
Tomas By's user avatar
  • 218
1 vote
2 answers
5k views

Raspberry Pi 3B+ RTC and Power ON button

I have a RTC DS3231 connected to my Raspberry Pi 3 B+. I connected it using this tutorial https://www.raspberrypi-spy.co.uk/2015/05/adding-a-ds3231-real-time-clock-to-the-raspberry-pi/ and everything ...
Unxcellent's user avatar
0 votes
1 answer
2k views

Problem using RTC using ds3231

Trying to get an RTC to load at boot. I've enabled i2c, that works fine for other components. /etc/modules contains: snd-bcm2835 i2c-bcm2835 i2c-dev rtc-ds3231 /etc/rc.local contains: echo ...
zotty's user avatar
  • 101
1 vote
1 answer
468 views

How to hack power bank with timer to power cycle Raspberry Pi

... without an Arduino (if possible). I am aware there are well-made solutions like the WittyPi, RTC-Arduino circuits, and some others with relay switches. If a power bank is directly connected to ...
E-Tan's user avatar
  • 11
1 vote
1 answer
1k views

pigpio bitbang i2c returns random data, smbus is OK

The scripts and the results mostly speak for themselves. smbus returns good data when I use the standard I2C GPIO pins, but the pigpio bit banging I2C returns what looks like random data. What might ...
uhoh's user avatar
  • 552
6 votes
5 answers
5k views

Do I need an RTC if my Raspberry Pi is continuously connected to the Internet?

How accurate would the time on my Raspberry Pi 3 be if it is continuously connected to the Internet, but without an RTC?
ON5MF Jurgen's user avatar
2 votes
3 answers
1k views

rtc DS3231 not updating system with new raspbian GNU Linux 9 stretch

Just updated to Raspbian stretch and my ds3231 will not update the system clock on reboot - i suspect that the command /sbin/hwclock -s is not working in /etc/rc.local - if I just do the update ...
Paul's user avatar
  • 21
1 vote
1 answer
1k views

real time clock problem -- why do I have endless rtc0/subsystem/rtc0/subsystem

I'm having trouble with a Pi-Zero rebooting after a varying number of hours. It's not crashing, it's rebooting, so there must be a reason for its madness. I see this in syslog minutes or hours before ...
NewtownGuy's user avatar
1 vote
0 answers
332 views

How do you change the output of sudo hwclock?

Just recieved a new RTC for my Raspberry Pi. When I use the sudo hwclock command the output looks like the following: 2018-01-08 13:06:5.441956+0100 On my other Raspberry Pi’s the output looks like:...
user75374's user avatar
3 votes
1 answer
2k views

Windows 10 IoT does not automatically use the Real Time Clock module to automatically update the system time

bought a brand new Raspberry Pi 3 DS3231 RTC Module and integrated to correct gpio pins as it should be. But somehow Windows 10 IOT seems not detect this module. than attempted to follow follow ...
Zen Of Kursat's user avatar
2 votes
1 answer
1k views

Why is PCF8563 not recognized on Raspberry Pi 3?

I'm using a HAT that among other things has a PCF8563 real-time clock on it (fed by a supercap when the Pi is off.) I can use i2cdetect to see the device on bus 1, but the rtc-pcf8563 module does not ...
Jon Watte's user avatar
  • 123
1 vote
1 answer
625 views

Available RTC modules

I know the procedure to enable an external RTC, but I just wonder which are the available supported chip (in config.txt and to use with modprobe). Where can I find such a list?
Mark's user avatar
  • 523
0 votes
1 answer
1k views

rtc module in Raspbian Stretch

I'm following this guide to set up the rtc module in Raspbian Stretch. First question: after the changes described, the RPi doesn't sync anymore with the actual time from the Internet. Second ...
Mark's user avatar
  • 523
2 votes
0 answers
369 views

RTC ds1307 module losing time

I am trying to get the rtc i2c ds1307 module working under Raspbian Jessie. I followed these guide to let the raspberry recognize the module and set it up. Fortunately everything works great. I can ...
linux_lover's user avatar