Troubleshooting UART Selection for Arduino Mega using MegaCore

Development Tools Uploading
1

Issue Overview:

I'm encountering difficulties when attempting to use UART other than UART 0 and UART 1 for uploading programs to the Arduino Mega using MegaCore (Idea came from: Uploading sketch to Mega 2560 through serial2 or serial3?). Specifically, I suspect the problem lies with the autobaud rate detection, as mentioned in the readme of MegaCore.

Relevant Information from MegaCore Readme:

The readme for MegaCore states:

Make sure you connect an ISP programmer, and select the correct one in the "Programmers" menu. For time-critical operations, an external crystal/oscillator is recommended. The Urboot bootloader has automatic baud rate detection (except when using UART2 and UART3 on ATmega640/1280/2560), so UART uploads should work fine even though the oscillator is a little too fast or too slow.

Detailed Log Comparison:

Here's a comparison of the log for selecting UART 0 vs. UART 3:

UART 0:

avrdude: AVR device initialized and ready to accept instructions
avrdude: device signature = 0x1e9801 (probably m2560)
avrdude: Note: flash memory has been specified, an erase cycle will be performed.
         To disable this feature, specify the -D option.
avrdude: erasing chip

avrdude: processing -U flash:w:~/Library/Arduino15/packages/MegaCore/hardware/avr/3.0.1/bootloaders/urboot/atmega2560/watchdog_1_s/autobaud/uart0_rxe0_txe1/led+b7/urboot_atmega2560_pr_ee_ce.hex:i
avrdude: reading input file ~/Library/Arduino15/packages/MegaCore/hardware/avr/3.0.1/bootloaders/urboot/atmega2560/watchdog_1_s/autobaud/uart0_rxe0_txe1/led+b7/urboot_atmega2560_pr_ee_ce.hex for flash
         with 396 bytes in 2 sections within [0x3fe00, 0x3ffff]
         using 2 pages and 116 pad bytes
avrdude: writing 396 bytes flash ...
Writing | ################################################## | 100% 0.16s
avrdude: 396 bytes of flash written
avrdude: verifying flash memory against ~/Library/Arduino15/packages/MegaCore/hardware/avr/3.0.1/bootloaders/urboot/atmega2560/watchdog_1_s/autobaud/uart0_rxe0_txe1/led+b7/urboot_atmega2560_pr_ee_ce.hex
Reading | ################################################## | 100% 0.00s
avrdude: 396 bytes of flash verified

avrdude: processing -U lock:w:0xff:m
avrdude: reading input file 0xff for lock
         with 1 byte in 1 section within [0, 0]
avrdude: writing 1 byte lock ...
avrdude: 1 byte of lock written
avrdude: verifying lock memory against 0xff
avrdude: 1 byte of lock verified

avrdude done.  Thank you.

UART 3:

       Programmer Type : STK500
         Description     : Atmel STK500 version 1.x firmware
         Hardware Version: 2
         Firmware Version: 1.18
         Topcard         : Unknown
         Vtarget         : 0.0 V
         Varef           : 0.0 V
         Oscillator      : Off
         SCK period      : 0.1 us
avrdude: AVR device initialized and ready to accept instructions
avrdude: device signature = 0x1e9801 (probably m2560)
avrdude: Note: flash memory has been specified, an erase cycle will be performed.
         To disable this feature, specify the -D option.
avrdude: erasing chip

avrdude: processing -U flash:w:~/Library/Arduino15/packages/MegaCore/hardware/avr/3.0.1/bootloaders/urboot/atmega2560/watchdog_1_s/external_oscillator/16000000_hz/115200/uart3_rxj0_txj1/led+b7/urboot_atmega2560_pr_ee_ce.hex:i
avrdude fileio_segments_normalise() OS error: cannot open input file ~/Library/Arduino15/packages/MegaCore/hardware/avr/3.0.1/bootloaders/urboot/atmega2560/watchdog_1_s/external_oscillator/16000000_hz/115200/uart3_rxj0_txj1/led+b7/urboot_atmega2560_pr_ee_ce.hex: No such file or directory
avrdude do_op() error: read from file ~/Library/Arduino15/packages/MegaCore/hardware/avr/3.0.1/bootloaders/urboot/atmega2560/watchdog_1_s/external_oscillator/16000000_hz/115200/uart3_rxj0_txj1/led+b7/urboot_atmega2560_pr_ee_ce.hex failed

avrdude done.  Thank you.

Failed to burn bootloader: uploading error: exit status 1

Error Encountered with UART 3:

avrdude ioerror() OS error: file ~/Library/Arduino15/packages/MegaCore/hardware/avr/3.0.1/bootloaders/urboot/atmega2560/watchdog_1_s/external_oscillator/16000000_hz/115200/uart3_rxj0_txj1/led+b7/urboot_atmega2560_pr_ee_ce.hex is not readable: No such file or directory

Is there anything I can do to resolve the issue?

2

Hi @agingwarrior. This is caused by a bug in the MegaCore boards platform configuration. This particular bootloader file is at a different path than the path specified in the platform's configuration

I submitted a fix for it:

I think the easiest workaround for the bug will be to move the bootloader file to the path where the platform is configured to look when performing a "Burn Bootloader" operation:

  1. Use macOS Finder to navigate to the following path:
    /Users/foo/Library/Arduino15/packages/MegaCore/hardware/avr/3.0.1/bootloaders/urboot/atmega2560/watchdog_1_s/external_oscillator/16000000_hz/
    :exclamation: The Library folder is hidden by default. You can make it visible by pressing the Command+Shift+. keyboard shortcut.
  2. Rename the 115200_baud folder to 115200.

Now try performing a "Burn Bootloader" operation in Arduino IDE just as you did before. Hopefully this time it will be successful.

3

Thank you so much. I've been able to get it working now.

4

You are welcome. I'm glad it is working now.

Regards,
Per

5

This topic was automatically closed 180 days after the last reply. New replies are no longer allowed.