Arduino Due Bootloader UART

Official Hardware Mega Due
1

I would like to access the Arduino Due bootloader directly via UART (Rx0/Tx0) pins on the board.
The SAM reset sequence regarding erase/reset is known and works fine.
I connected an external USB-UART interface and picked up the signal with a logic analyzer.
The Rx0 Pin of the Due is always in high state and never goes to low state.
If I connect the external USB-UART interface to Rx1, then everything works normally and I can see the UART communication.
My guess is that the level converter (74LVC1G125DBV) on the Due between 16U2 and SAM always sets the signal to high.
Can anyone confirm my suspicion or have a solution for me?

Background
The Arduino Due is the sub controller of my Raspberry Pi and must also be programmable/debugable via the pi.
There is no space for a USB cable in my project and the Due must also run when the raspberry is powered off.

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You are right, but I would suggest a different method. You could use RPI as SWD programmer with OpenOCD.

1 Like
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Damned!
I didn't want to hear this kind of answer :smiley:

Thanks for the tip about the SWB interface!
I don't have any experience with SWD and was hoping for a simpler solution :slight_smile:

I couldn't find a quick tutorial and openocd seems to need chip-specific settings.

If anyone has experience with this, I would be very grateful for any advice.

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