ESP32 Forum

Greetings, I have a header on my board design for programming with an FTDI, I am using the same basic circuit shown in Espressif schematics for 2 transistors on for DTR / RTS, now my setup works fine, until I turn on WiFi, then the ESP32 just crashes and restarts or freezes, UNLESS I plug in the FTDI (It doesn't even have to be plugged into USB and powered!), then it runs smooth! NO idea why this is. I checked and my grounds are fine, I am not using power from the FTDI so that isn't the problem. This is really perplexing to me. I did test my design and found infinite resistance between DTR / RTS control lines and ground or 3.3V VCC, same for TX/RX, with FTDI plugged in but no USB or power to it directly I read 35M resistance between GND and DTR and RTS, AND 35M from FTDI VCC to DTR / RTS, which leads to a 2.5V potential on the pins (with no USB cable connected), and 232k between VCC and GND on the FTDI. Again this is with FTDI NOT powered, but my ESP32 will rfun stable and fine. If I don't use WIFI then it will run stable and fine reguardless. It can't be a power supply issue as 1: It's stable with the FTDI plugged in and no power to it (also I am using a huge 5000mAh 3 cell Lithum battery and a power supply rated to 5A @ 12V), I have 2A 5V buck which is running fine, 1117 for 3.3V which is also fine.

I have tried pull ups AND puill downs on the DTR / RTS lines, and that makes no difference, I am really stumped.

As a follow up to anyone else who may encounter this, putting a 100nF cap and a pull up before RTS transistor solved the problem.

I too found behavior like MatCat for a ESP32 board designed by another vendor.

Might anyone have a schematic for the fix that MatCat described?

Thanks.