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).
292 questions
0 votes
2 answers
70 views
RTC M41T94 reset in the temperature cycle test
We are using the M41T94 RTC IC in our board. In the temperature test, we are observing the RTC reset. Reset to the initial date and time. This is causing the log and data mismatch. Test Details: ...
-1 votes
0 answers
47 views
STM32H7 RTC loses data after long power-off – could a Schottky diode on VBAT be the cause?
I’m having an issue with the RTC on an STM32H743BIT6 on a custom PCB. The VBAT pin is connected to a battery (CR2032). I set the correct time and date in the MCU, then power off the main supply. After ...
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1 vote
1 answer
84 views
How long does a ds3231 rechargeable battery last without charging
I've built a (bird) sound record around an ESP32 with a DS3231 RTC for accurate time stamping. The recorder goes into deep sleep mode when not actually recording, which is typically set to 3 minutes ...
- 111
2 votes
2 answers
269 views
RTC battery and VCC switching circuit
The circuit shown below is used on one of my PCBs to switch the VBAT supply for the RTC, ensuring timekeeping continues whenever the main supply (VCC) is unavailable. Circuit Operation Under normal ...
- 560
1 vote
1 answer
106 views
Real Time Clock Battery Life
As part of my design, I have a DS3231 RTC with the following schematic implementation snippet: The (bottom side)layout looks like this: SCL and SDA are pulled up to +3V3. Coin Cell battery (+) is ...
- 23.1k
3 votes
2 answers
275 views
DS1339 - Backup Battery
Does anyone know why the datasheet (DS1339) states that proper operation isn’t guaranteed if a series diode is placed between the battery and the VBACKUP pin?
- 674
1 vote
1 answer
114 views
ESP32 Built-in RTC vs External RTC for Offline Timekeeping in Projects
I’m working on a project using the ESP32 microcontroller where accurate timekeeping is essential for performing time-based calculations and logging, even without internet access. In this scenario, I’m ...
- 11
0 votes
0 answers
58 views
Will ESP32-C3-WROOM be able to keep the TPS61040DBVR IC off in deep sleep mode?
I'm told that GPIO3 is an RTC pin, capable of saving its state even if the ESP32-C3 enters deep sleep mode. Here's my thinking: I want to have the chip on by default, so I'll pull the EN pin high ...
0 votes
0 answers
59 views
DS1302 RTC chip stops on battery power
I am working on a project, where I have a Raspberry Pi Pico and then a DS1302 chip to keep time when the pico is not powerer. The whole thing is powered by a single lithium battery. The battery powers ...
1 vote
0 answers
46 views
MAX31329 Backup Battery Discharging
Recently, I changed an old design to use the MAX31329 instead of the DS model, because of it's lower timekeeping current requirement. Instead of using the trickle charger setting I opted into charging ...
- 11
1 vote
0 answers
100 views
Using microcontroller-integrated ADC vs dedicated ADC component (ESP32-S3)
I'm a novice to PCB design and circuit design. For an university project, I need to design a PCB which samples 16 different signals at a rate of 800Hz per signal (ie need total sample rate 16x800=...
- 197
0 votes
2 answers
173 views
Replacment for supercapacitor
I have a design that uses a Elna super capacitor to backup a real time clock (RTC). The supercap is being discontinued and I can't find a suitable replacement. It seems this entire market is shutting ...
- 109
1 vote
0 answers
97 views
Help to identify mystery MCU [closed]
I'm trying to add an RTC backup battery to Vbat pin of the microcontroller inside an LED lamp controller, because, when there's power outage, the controller is crippled due to reset clock. ...
- 19
5 votes
2 answers
1k views
Get Time-of-day from computer onto a USB connected connected device
Is there a standard way to retrieve Time-of-day onto a "dongle" connected to a computer over USB? My IoT device is connected over USB for power, but has data connection pins (for firmware ...
- 151
1 vote
1 answer
112 views
STM32 RTC Issues When Powered with Transformer
I am currently trying to figure out a problem that I couldn’t understand the reason for. Here is the schematic of the circuit: Last weekend, I soldered a PCB on a prototype board. The circuit ...
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