Hard-reset not working

tatulea
Posts: 14
Joined: Wed Feb 06, 2019 12:39 pm

Hard-reset not working

Postby tatulea » Thu Aug 15, 2019 10:34 am

Hi,

I have a custom board with a ESP-WROVER-B. There is a CP2102N that has the reset and boot circuit implemented as it is in the ESP-DevkitC schematic (RTS, DTR, two transistors, EN and IO0).

The first problem that I had was the fact that my board was not getting into "download mode" in order to flash it. For now, it looks like this was solved by adding a capacitor between EN and GND. After this, the flashing is working, but the hard-reset is not. I had a look here (https://github.com/espressif/esptool/issues/399) and I added time.sleep(2). It looks like it's working.

My CP2102N is A01 revision and it seems to be a hardware problem and because of this the hard-reset is not working.
I also have an ESP-DevKitC which has the same A01 revision and the v4 schematic of it uses A01 as well. The question is, why the hard-reset is working with A01 on DevKitC, but not on my board?

Nikonov_94
Posts: 5
Joined: Fri Jul 26, 2019 6:20 pm

Re: Hard-reset not working

Postby Nikonov_94 » Mon Aug 19, 2019 2:58 pm

Oh, that's great you asked, I was in the process of ordering an A01 revision CP2102N bridge... Is this issue recurrent with all of these models, and if yes, can it be solved? If no, what would be a good alternative?

captain_morgan
Posts: 34
Joined: Wed Dec 09, 2015 6:39 pm

Re: Hard-reset not working

Postby captain_morgan » Mon Aug 19, 2019 3:53 pm

I'm using this part successfully in several of my designs. First thing I notice in your description is your reset circuit, typically this is implemented with two transistors and two resistors. Here's one of my recent schematics https://cdn.hackaday.io/files/163861701 ... coffin.pdf. Additionally you mention the cap on EN, do you have a pull-up resistor on EN also? I found missing this caused really inconsistent flashing in an early design.

If these don't help you should post the schematic of your CP2102 circuit for further help. But other things to check...
What's the voltage on VDDIO?
VBUS connected? (Ignore my voltage divider, turned out unneeded)
RSTb pulled high? (specifically to VDDIO)

ESP_Angus
Posts: 1790
Joined: Sun May 08, 2016 4:11 am

Re: Hard-reset not working

Postby ESP_Angus » Tue Aug 20, 2019 3:53 am

tatulea wrote:
Thu Aug 15, 2019 10:34 am
hard-reset is not. I had a look here (https://github.com/espressif/esptool/issues/399) and I added time.sleep(2). It looks like it's working.
If the sleep here fixes the problem, and you need to power cycle the CP2102N to get it back otherwise, then it almost certainly is this hardware issue. Driver updates have been released for macOS and Windows to fix this, but Linux still does not have one - so the only known fix on Linux is to update to A02 silicon or downgrade to a CP2102 chip.

If you're using one of the other OSes, try updating your drivers.

captain_morgan
Posts: 34
Joined: Wed Dec 09, 2015 6:39 pm

Re: Hard-reset not working

Postby captain_morgan » Tue Aug 20, 2019 4:00 am

Interesting.... and maybe a bit concerning? I'm using the CP2102N-A01 and have no issue flashing from several different Linux machines. Do you have any further reading on this issue?

ESP_Angus
Posts: 1790
Joined: Sun May 08, 2016 4:11 am

Re: Hard-reset not working

Postby ESP_Angus » Tue Aug 20, 2019 4:05 am

The github issue link above has a fairly good summary of my understanding of the problem, and a link to a SiLabs forum post reporting the problem.

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