Trying to design an ESP32 dev board

[liudr]

One more thing, how do I keep the time between power cycles?

The processor has an RTC power pin but the WROOM module has connected it to VCC:



How am I supposed to get a coin battery connected to it? A separate RTC IC I guess?

What does lobo's port do with RTC?

[OutoftheBOTS_]

We know that it works even with the delay but what confused me was the assumption everyone makes

When DTR is set LOW and RTS set HIGH, this disconnects RESET from the transistor and it gets pulled HIGH by the external pullup resistor. At the same time, GPIO0 is pulled to LOW by the transistor

At the same time, just isn't true. From the code in esptool.py

Code: Select all

self._port.setDTR(True)   # IO0=LOW
self._port.setRTS(False)  # EN=HIGH, chip out of reset

This is 2 lines of code and they don't get executed at the same time. What happens is first line of code is executed and DTR goes high and RTS is still high then after it has finished then RTS goes low. So in real life the transition will be like Roberthh saw on his scope.

[OutoftheBOTS_]

Laboris wiki on RTC https://github.com/loboris/MicroPython_ ... o/wiki/rtc

If your asking to to maintain data or time during powering down VDD. I think most people are syncing the time when it connects to the internet on power up. If you need data saved you can always create a temp file on the flash

[loboris]

One more thing, how do I keep the time between power cycles?

The processor has an RTC power pin but the WROOM module has connected it to VCC:
How am I supposed to get a coin battery connected to it? A separate RTC IC I guess?

On every ESP32 board and module I know about VDD3P3_RTC is connected to VDD33, so, unless you design you own board with a bare ESP32 chip, you cannot attach the backup battery to this pin.

But, it doesn't have to be a problem. Well designed board will have less than 10 uA power consumption in deepsleep mode (in which the RTC is still running and the time is preserved), so you can run your bord connected to power source all the time.
When you remove the power, you should synchronize the time from NTP server after first boot.

You can use some I2C RTC chip with backup battery, but it is usually not necessary and actually doesn't make much sense.