ESP-WROOM-32 & SDMMC & CH340G

don.vukovic
Posts: 31
Joined: Tue Mar 21, 2017 3:40 am

ESP-WROOM-32 & SDMMC & CH340G

Postby don.vukovic » Mon Jul 01, 2019 1:23 am

I need some advice.
I have designed a PCB using a ESP-WROOM-32 & SDMMC & CH340G.
The problem is that the CH340G uses the two transistors for set the programming mode.
If I have an SD card inserted into it's socket, the WROOM will not go into programming mode.
I release the SD card, and its fine.

Is there a correct schematic where the SD card does not interfere with the Boot process.
I know its the IO2 pin.
What is the proper circuit ?

The schematic attached is my pcb schematic.
SDMMC.pdf
(28.89 KiB) Downloaded 662 times

ESP_igrr
Posts: 2071
Joined: Tue Dec 01, 2015 8:37 am

Re: ESP-WROOM-32 & SDMMC & CH340G

Postby ESP_igrr » Mon Jul 01, 2019 1:56 am

Please have a look at the wrover-kit schematic (https://docs.espressif.com/projects/esp ... s.html#id8). It has the additional transistor on GPIO2 to pull it low when entering download mode.

don.vukovic
Posts: 31
Joined: Tue Mar 21, 2017 3:40 am

Re: ESP-WROOM-32 & SDMMC & CH340G

Postby don.vukovic » Wed Jul 03, 2019 8:28 pm

I added the extra isolation transistor, but I have the same proble.
I can not go into programming mode with the SD card inserted.

Please see attached schematic.
Attachments
SDMMC_070319.pdf
(28.73 KiB) Downloaded 591 times

WiFive
Posts: 3529
Joined: Tue Dec 01, 2015 7:35 am

Re: ESP-WROOM-32 & SDMMC & CH340G

Postby WiFive » Thu Jul 04, 2019 12:08 am

Did you check oscilloscope? Maybe EN pin goes high before IO2 goes low because of no cap on EN + strong pull-up, and capacitive effects of SD card on IO2?

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