11 Comments

    • ryan

      Richard,

      JTAG is enabled on all the Raspberry Pi boards. The pins are on the GPIOs but need to be set to alternative function. By following the steps in this guide, you will be able to utilize JTAG. Are you having difficulty with any of my instructions that I can assist you with?

      Ryan

      • Alexandre

        Hi,

        I’m trying something pretty similar but in bare metal context, no OS. At boot I enable the necessary GPIO for JTAG (24, 25, 26, 27) but my debug module (RPi HUB module from FTDI) is unable to get any feedback from the PI2. The TDO line keeps always high.
        I wonder if really JTAG is enabled on all PI boards :/
        Doesn’t it depend on the proc mode (my PI2 boots in HYP mode) ? Or any hidden feature in the bootcode.bin program would prevent the JTAG cell to reply ?
        Thanks for any ideas.

        • ryan

          How are you enabling the GPIOs for JTAG? Do you have the proper interface configuration file for the RPi HUB and OpenOCD? JTAG is enabled on all models, all that needs to happen is for the GPIOs to be set to their proper ALT functions. Are you using OpenOCD?

  1. Richard Helgeson

    I want to use an Atmel Dragon programmer to download code and use the Pi as a bare- metal embedded controller.

    I want to bypass any operating system and boot directly to the application.

    Can this be done?

    • ryan

      In theory yes, you’ll probably need to do a soft_reset_halt in OpenOCD and clear all the registers and wipe the memory, then load your application. I’m not too familiar with the Atmel Dragon Programmer but if it uses standard JTAG protocol, it shouldn’t be an issue. There’s an example blink.elf somewhere on GitHub that serves as a bare-metal/GPIO example.

  2. required

    Can we crack the video codecs with this ? I’m running a hash farm for several weeks and I have no match results yet. I thing it’ll be more straightforward, or maybe we can glitch the runtimes into borking the comm.

  3. tatery

    I wonder if it is possible to configure JTAG on raspberry pi3 with raspbian on board and use it to program other devices directly from the same PI (without any additional PC with Linux or Windows).

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