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ESP07 not waking up from deep sleep

PostPosted: Mon Jul 26, 2021 10:44 am
by John Karij
I have a bare ESP07 module and I’m trying to use deep sleep.
It’s connected on a bench power supply and has external antenna connected.
I have soldered pullup resistors on GPIO0, 2, EN, RST, and a pulldown on GPIO15.

Normally it consumes about 70mA. It enters sleep mode but it doesn’t waking up fully. It starts getting 30mA and hangs there. I’ve read about zombie mode and that’s probably where I’m stuck to.

I tried to connect GPIO16 with RST using a jumber, or resistors from 200 to 2kΩ, or a rectifying diode(didn’t have a schottky in hand) with no luck. I also tried to remove the pullup resistor on RST.

I checked with a simple PC oscilloscope and GPIO16 is high during sleep. Sometimes I was able to catch a small low pulse (about 150μs) but even then the ESP wasn’t able to boot. Most of the times I don’t see the small low pulse from GPIO16. I think that I’m able to see this pulse if I probe GPIO16 without connecting it to RST.

What else could I check?

Re: ESP07 not waking up from deep sleep

PostPosted: Tue Jul 27, 2021 6:26 am
by btidey
The RST line on most ESP modules has a pull up resistor AND a capacitor to GND. The latter helps ensure the RST line is low for a period after power up.

This capacitance can smooth out a wake up pulse and prevent the chip from rebooting properly. You should be able to observe the pulse shape with your oscilloscope but probably want to set the trigger level manually to be just below the 3.3V Vdd level to catch any pulse that occurs.

You either need a low impedance pulse into the RST line or an alternative method is to use the EN (CH/PD) signal instead to perform the wake up. This signal will also reboot the chip when pulsed low but will not normally have capacitor attached so is much easier to drive.

Re: ESP07 not waking up from deep sleep

PostPosted: Fri Aug 27, 2021 9:32 am
by eriksl
I have also seen this behaviour when the ESP can't draw enough power on boot. On startup (also from deep sleep) it will need shortly a lot of power (~ 500 mA). If it can't get it, it will not boot properly. Make sure you have a proper voltage regulator or dc/dc converter that can actually supply this amount of power and also make sure you have a large enough capacitor crossing the power input.