# Can't upload to a Pro Mini with MiniCore/Urboot Bootloader using FTDI **URL:** \ **Category:** Uploading\ **Created:** [July 7, 2025, 11:20am UTC](https://forum.arduino.cc/t/cant-upload-to-a-pro-mini-with-minicore-urboot-bootloader-using-ftdi/1394115 "2025-07-07T11:20:44Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![seilo](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/seilo/32/1129942_2.png) [@seilo](https://forum.arduino.cc/u/seilo)\ **Post date:** [July 7, 2025, 11:20am UTC](https://forum.arduino.cc/t/cant-upload-to-a-pro-mini-with-minicore-urboot-bootloader-using-ftdi/1394115/1 "2025-07-07T11:20:44Z")
Hello forum! I now spent multiple hours on this and can't seem to find the problem... **Setup** Arduino IDE 2.3.6 Board: Arduino Pro Mini 5V/16MHz (clone) Using FTDI232 board as programmer I am following this instruction with the same hardware: > **[Programming the Arduino Pro Mini • Wolles Elektronikkiste](https://wolles-elektronikkiste.de/en/programming-the-arduino-pro-mini)** > > Sketches can be uploaded to the Arduino Pro Mini using USB-to-TTL converter modules. How to do this and how to solve problems are described. **Problem** The setup worked as expected with the stock bootloader it came with. However, for my application I want to code to start _fast_ once power is supplied. Unfortunately this is not the case with the preinstalled bootloader, which takes about 2s after power on until the sketch starts. On this forum I found a hint that Optiboot eliminated that additional time on power-up. Following the trail on github it directed me to MCUdudes MiniCore, which in turn uses Urboot. I successfully flashed MiniCore using ArduinoISP using an Arduino Uno. Settings: - Baud Rate: Default (also tested 57600) - BOD: 4.3V - Bootloader: Yes (UART0) Clock: External (16 MHz) - EEPROM retained - Compiler LTO enabled However, with the MiniCore bootloader in place, I cannot program the Pro Mini anymore using the normal upload function. Here is the error. ```arduino avrdude: Version 6.3-20190619 Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/ Copyright (c) 2007-2014 Joerg Wunsch System wide configuration file is "C:\Users\Seilo\AppData\Local\Arduino15\packages\arduino\tools\avrdude\6.3.0-arduino17/etc/avrdude.conf" Using Port : COM4 Using Programmer : arduino Overriding Baud Rate : 57600 avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0xa0 avrdude: stk500_getsync() attempt 2 of 10: not in sync: resp=0x77 avrdude: stk500_getsync() attempt 3 of 10: not in sync: resp=0xa0 avrdude: stk500_getsync() attempt 4 of 10: not in sync: resp=0x77 avrdude: stk500_getsync() attempt 5 of 10: not in sync: resp=0xa0 avrdude: stk500_getsync() attempt 6 of 10: not in sync: resp=0x77 avrdude: stk500_getsync() attempt 7 of 10: not in sync: resp=0xa0 avrdude: stk500_getsync() attempt 8 of 10: not in sync: resp=0x77 avrdude: stk500_getsync() attempt 9 of 10: not in sync: resp=0xa0 avrdude: stk500_getsync() attempt 10 of 10: not in sync: resp=0x77 avrdude done. Thank you. Failed uploading: uploading error: exit status 1 ``` **What I also tried:** - To cross-check, I switched the Pro Mini with another one (old bootloader, leaving the rest of the setup as-is) and all works as expected. This hints to me, that the FTDI232 programming might not be supported with MiniCore bootloader. Is that correct? I read something about a different reset timing. Might that be the problem? I am using the DTR output of the FTDI. - Rolling back to the Arduino standard bootloader, everything works fine Please let me know if any info is missing, I'll supply that. ---
**Author:** ![seilo](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/seilo/32/1129942_2.png) [@seilo](https://forum.arduino.cc/u/seilo)\ **Post date:** [July 7, 2025, 11:32am UTC](https://forum.arduino.cc/t/cant-upload-to-a-pro-mini-with-minicore-urboot-bootloader-using-ftdi/1394115/2 "2025-07-07T11:32:02Z")
As it goes sometimes...I found the solution a few minutes after posting this thread: I had select the **Arduino Pro or Pro Mini** as a board for the target application. It seems like I have to also use **MiniCore -\> ATMega328** for the sketch itself. I thought that was only used during bootloader flashing...stupid me for not having tried that earlier. ---
**Author:** ![system](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/system/32/1140315_2.png) [@system](https://forum.arduino.cc/u/system)\ **Post date:** [January 3, 2026, 11:32am UTC](https://forum.arduino.cc/t/cant-upload-to-a-pro-mini-with-minicore-urboot-bootloader-using-ftdi/1394115/3 "2026-01-03T11:32:46Z")
Closed on January 3, 2026, 11:32am UTC This topic was automatically closed 180 days after the last reply. New replies are no longer allowed.