ESP32 Forum

I see many references on implementing an auto upload circuit for the ESP32.
Most are variants of this circuit:
Having set the back-story, my question is this: The Arduino IDE is using a USB to Serial Module (model unspecified) to send the program to the ESP32 in response to the GUI Upload command. How, when and by What are the DTR &/or RTS signals generated?

If the Arduino Upload was being handled by the "Upload by Programmer" I would go looking for an answer in the programmers.txt file.

An additional confusion to me (not very difficult!), if I look to a genuine FTDI TTL-232R device (https://www.farnell.com/datasheets/814049.pdf), the DTR control line is not shown?

Regards, Martin

Use another type usb/serial converter/adapter. Before buy check connector pinout, or chip type on adapter.
In adapter if not wire the required signal to connector, then wire directly from chip pin.
Check power/gpio voltage level on adapter, and select 3V3 type.
I use simple wiring, RX,TX, GND, RTS to EN(reset), DTR to GPIO0

Hi,
Thank you for the response.
When you say: "I use simple wiring, RX,TX, GND, RTS to EN(reset), DTR to GPIO0"
Do you mean that RTS is connected DIRECTLY to EN? You are not using any interface or timing circuitry?
Like this?
Regards, Martin

Yes, directly. I use this ch340 adapter https://www.aliexpress.com/item/3278945 ... 4c4dl0bJvQ This adapter connector does not have a DTR signal but a wire soldered directly to the ch340 pin, The power jumper select 3,3V position on adapter. The usb 5V power signal is connected to the esp32cam module's 5V power supply

Thank you.

All understood & working now.

Regards,

pipi61 wrote: ↑

Fri Mar 13, 2020 6:32 pm

Use another type usb/serial converter/adapter. Before buy check connector pinout, or chip type on adapter.
In adapter if not wire the required signal to connector, then wire directly from chip pin.
Check power/gpio voltage level on adapter, and select 3V3 type.
I use simple wiring, RX,TX, GND, RTS to EN(reset), DTR to GPIO0

This works I have been trying to get a 100% reliable circuit for auto upload and have been tinkering with different resistor/capacitors for RC timing, different topologies etc. Now that I found your comment and simply connected RTS -> EN and DTR -> IO0 it's working flawlessly.

This saved me my sanity, thank-you!