Setup: Arduino IDE 1.8.13, Arduino AVR boards 1.8.6, using Pro Mini 328P 16MHz.
It has been a while since I programmed this board, then using a CP2102 UART. Uploading used to be by pressing the RST button until compile was done and ready to upload, when RST is to be released.
When using the Optiboot bootloader this still works, yet not with the regular Arduino AVR 1.8.6 board selection.
Why is that?
I use Tools>Board Arduino Pro or Pro Mini and select the correct board
here I am using a 3.3V 8Mhz module
Hi horace, do you use DTR? I don't, I have a CP2102 UART without that pin and managed to get the Pro Mini programmed with the RST button "trick". Is that still valid?
That should still be valid. Timing however might be a bit tricky (as it always has been).
I use a FTDI TTL-232R-3V3 USB cable or a breakout board
not sure if we are talking about the same thing
Op might be using something like below
Just to demonstrate that there are boards that don't have all required signals.
@sterretje Yes, that is the UART I am using indeed.
And glad to hear the "RST button trick" still works; release timing indeed is the critical aspect as I just found out. Thanks!
You actually don't have to keep the board in reset. Just before (or at the moment that) the IDE reports the memory usage you can tap the reset button.
Life is a lot easier with an adapter that provides all needed signals 
But that is your call.
But not all Pro Mini's have the DTR brought outside.
They actually should; if it doesn't, it's (officially) not a Pro Mini 
See the schematic: https://www.sparkfun.com/datasheets/DevTools/Arduino/Arduino-Pro-Mini_328-v11.pdf
So buy a programmer that does.......gees, they must be all of $2 these days or..........mod your existing one.
It will possibly require more if the so-called Pro Mini does not have the DTR pin broken out.
@sterretje , what do you mean? As far as I know, with Vcc, GND, TX and RX connected a programming on Pro Mini should work with correct timing of release of the RST button once compile is finished and ready for download?
Apparently, from all the schematics I looked at, the DTR is simply a 0.1uf to the reset with a 10k pullup.
Not sure what you're referring to. Indeed it can be done the way that you do it. Only thing that I tried to say is that you don't have to keep the board in reset the whole time, only press and release the reset button just the upload starts.
@sterretje ah ok, that is what I had assumed and thanks for confirming sterretje 
@brice3010, sorry for the little off topic question, but I would like to ask @horace what piece is that:
Looks like some kind of a female-male Dupont cable connector with 90º angle but the program pins on the Pro-mini side are not soldered at all. Is that correct? It's an interesting solution.
I replaced the 6 pin male connector on the Pro Mini with a 6 pin female connector
as the breakout board used to to program the Pro Mini has a 6 pin male connector it makes it easier to connect
@Brazilino ..or, if you prefer not to mod the Pro Mini pins, make a cable with a 5-pole Dupont female-to-female connector on each end that will fit both the male Pro Mini connector and the FTDI male pins.
