I have DIY sam3x8e pcb board based on schematics of Arduino Due. I can program it with Atmel-Ice (jtag connector) in Atmel Studio with basic serial transfer example and it works fine when the Atmel-ice is plugged in to the board. But when I unplugged it, the MCU doesn`t work. What are possible reasons for that?

I tested all the voltages across Sam3x8e power pins and they are all correct.

  • \$\begingroup\$ Check the nTRST and nSRST pins on your JTAG connector. Maybe you have terminated them incorrectly and thus the board stays in some sort of reset condition. Without the Atmel-ICE connected I would expect both signals to be HIGH. \$\endgroup\$
    – og1L
    Mar 4, 2016 at 15:22
  • \$\begingroup\$ Is it possible you're not pulling up the RESET line? (edit: og1L beat me). \$\endgroup\$
    – uint128_t
    Mar 4, 2016 at 15:23
  • \$\begingroup\$ Sam3x8e has internal pull-up resistors on reset pins, so why should I add additional ones? I tested those pins with multimetr and it is 3.3 volts there. Here is my schematic for reset pins, I use a jumper to select which reset pin I want to use: i65.tinypic.com/24fiwwp.png \$\endgroup\$
    – v_s_k
    Mar 4, 2016 at 15:36
  • \$\begingroup\$ @uint128_t You may be right about the lack of pull-up. I don't see the pull-up on the schematic snippet. \$\endgroup\$ Mar 4, 2016 at 16:32

1 Answer 1



It is necessary to connect gnd from usb-uart bridge to gnd on pcb, I was just using rx - tx line. When the Atmel-Ice was connected it provides ground from pcb to PC usb port through JTAG connector, that`s why it was working.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.