Problem with a Serial Port connection

Hi. I’m trying to get Marlin uploaded to Ender 3 printer. I followed a tutotial and the project builds just fine, but fails completely when I try Upload. In platformio.ini I set upload_port = /dev/ttyUSB0 as specified here. I use a mac. Any idea why the upload would fail? If I click on Serial Monitor it says Miniterm on /dev/cu.usbmodem14401 250000,8,N,1 --. Thanks

Seems like you’re running into the same problem as in Ender 3 (Pro) Marlin 2.0 Upgrade - Updated Version - YouTube, aka no bootloader installed on the chip.

Try using the procedure above or flash the firmware using an Arduino Uno (or other Arduino AVR board) as a “Arduino as ISP” programmer ( Either via the Arduino IDE or PIO as per docs.

Thanks for the suggestion. I was trying to flash it as you suggest before, but was suggested that BTT SKR Mini E3 V1.2 already comes with a bootloader on.

According it its schematic that is a STM32F103RC based printer board. You originally posted

which is (according to the schematics) an Atmel ATMega1284P based printer.

Which printer do you have?

It’s Ender 3 but the board has been replaced with BTT SKR Mini E3.

So that was very crucial information.

What Marlin repository and branch are you using with what environment and config files?

I’m using MarlinFirmware/Marlin/tree/bugfix-2.0.x. Here’s my platformio.ini and Configuration.h.

I’m on a Mac, using the PlatformIO IDE v1.10.0.

Why’d you choose

default_envs = LPC1768

which is for an NXP LPC1768 chip, shouldn’t that be a STM32F103RC_btt_XXX like environment?

I’ve followed this tutorial. I tried using STM32F103RC_btt_512K but it didn’t work.

Re- boot loader . Trying to upload onto MKS GEM L v1.0 is a book loader needed ? . Becoming confused, it’s a SERIAL PORT identified as ( com3 ) , not a USB PORT identified as( com 3 )