WEMOS D1 mini Pro - reset button crash mcu(?)

Other Hardware 3rd Party Boards
1

Hello,
I'm using a WEMOS D1 Mini Pro with ADS1115, OLED 1.3", RTC and MicroSD module.
The circuit is soldered to a drilled board and works fine, except that the Reset-Button doesn't work as expected.

Pressing the RST-Button seems to crash the mcu but at least stops the output to the serial monitor after displaying a few "random characters".
No exception output.
Only disconnecting and reconnecting the usb cable recovers the serial output.
The reset pin isn't connected at all.
For testing I removed all modules (OLED, RTC, ADC, MicroSD) - same result ...

Also tested a ftdi232 for serial connection and powered the board from usb adapter - same result, except, that only disconnecting power restores serial output.
Therefor I assume that pressing the reset button does crash the mcu ???

Any idea what's wrong???

2

Please post a schematic and a sketch that shows the problem

3

Part of screen shot from serial output (last row):

reset_serial_output
reset_serial_output759×468 9.62 KB

Circuit:

circuit
circuit1149×675 62.3 KB

4

And the sketch ?

5

You are right

Any idea what's wrong???

The Wemos designers didn't read the 8266 datasheet. They connected the reset button to the wrong pin

6

OK, thank you!
Could you please let me know how to work around?

Found this:

esp8266_wemos_reset
esp8266_wemos_reset958×792 106 KB

Not sure, if it's the correct version - my wemos is labeld with V1.1.0

What's wrong? RST is pulled up (12K) and rst button connects to GND, right?

7

From the ESP8266 hardware design guidlines:
We recommend that you use CHIP_EN, instead of EXT_RSTB, to reset the chip.
That is how Espressif does in on their devkit.
It's not clear what happens when you pull EXT_RSTB low while the IC is powered and CHIP_EN is high

8

OK, they may prefer the chip_en variant, but I also found this

esp8266ex_hw_guide_reset1
esp8266ex_hw_guide_reset1878×339 18.9 KB

However, with the wemos D1 mini I don't have direct access to the chip_en pin.
What can I do to prevent this misbehaviour?

Using the WEMOS D1 min pro only - not connected to my circuit board ("stand-alone"),
the reset works as expected.

Desolder R6 from WEMOS board?

9

@UKHeliBob
I don't think it's a software related problem, as the device works fine when not connected to my board.

10

Are you now saying your D1 is resetting even when you don't push the reset button?

11

No, sorry, ...

The wemos reset button works as expected when the wemos board is not plugged in to my circuit board.

This is my circuit board with the wemos plugged in ...

CPM_light_board_v001
CPM_light_board_v0011920×1080 131 KB

12

Are you now confused :wink:

13

I've propably found the reason ...

The ads1115 is running in "continuous mode", taking 8 measurements per sec., each one resulting in an interrupt, that pulls the Wemos port D3 (GPIO0) down which is connected to the ads1115 alert-pin.
Wemos gpio0 pulled low prevents the esp8266 from booting up.

14

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