I have made a custom board based on the Arduino Due but have some problems with the Serial communication with the 16u2 chip.
i have usb connection with the 16u2 chip and was able to load the arduino-due usb serial hex over the usb port. the usb now shows up as arduino com port. now when i try to load a sketch it says No device found on COM12. the SAM chip is erased but it can't load the new sketch.
now when i load a sketch with a simple serial print at 115200 over the native port. the SAM chip is programmed correctly. when i open the serial monitor i receive data but it is garbage! the garbage is always different. the sketch is at 115200 and the monitor also at 115200.
this would explain why it can't upload a sketch with the 16u2.
the same sketch on a original arduino due works fine.
the transmit an receive led are blinking.
What would cause this garbage in the connection where do i start looking?