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diff --git a/docs/source/jtag.rst b/docs/source/jtag.rst index e94229f..5301a18 100644 --- a/docs/source/jtag.rst +++ b/docs/source/jtag.rst @@ -4,4 +4,68 @@ JTAG ====== -Stub. +JTAG is an interface for low-level debugging of digital devices. It +gives instruction by instruction control over the microprocessor and +allows data to be read and written to arbitrary memory and register +locations. It is typically used with a debugging tool like `gdb +<http://www.gnu.org/software/gdb/>`_ when hacking low level routines +and hardware peripherals (we use it when working on :ref:`libmaple +<libmaple>`) or to flash a new bootloader. + +Note that the STM32 on the Maple has a built-in low level serial +debugger which could also be used to flash bootloaders, and that the +:ref:`ASSERT <language-assert>` framework allows basic debugging over +a USART serial channel. We expect only advanced users to use this +feature. + +.. contents:: Contents + :local: + + +Wiring Diagram +-------------- + +.. figure:: /_static/img/jtag-wiring.png + :align: center + :alt: JTAG wiring diagram + + JTAG wiring diagram to connect a standard 20-pin ARM JTAG device to + the 8-pin JTAG port on the Maple. + +.. TODO jtag wiring diagram (above) looks terrible; replace it + +The Maple has holes for a 8-pin JTAG header but that header is not +soldered on by default. If you know ahead of time that you'll be +needing it, and you order `straight from LeafLabs +<http://leaflabs.com/store/>`_, add a comment to your order and we can +probably solder one on for no charge. Otherwise, you can simply +attach standard 0.1" pitch male header pins (either the exact 4x2 +block or two 4-pin pieces of breakaway straight header). For a one-off +usage hack, the header can be jammed in the holes and twisted to +ensure electrical contact; this is what we do to flash our bootloader. + +The above schematic assumes that the header has been soldered on to +the *bottom* of the board, not the top; most ribbon cable connectors +will interfere with the power header. If you don't want a header +coming off the bottom, you can use a slim connector and invert this +diagram appropriately. + + +Compatible Devices +------------------ + +We have had good experience with the `Olimex ARM-USB-OCD +<http://www.olimex.com/dev/arm-usb-ocd.html>`_ device, which costs +about 55 euro plus shipping (as of October 2010). + + +Recommended Reading +------------------- + +* `Wikipedia Article on Joint Test Action Group (JTAG) <http://en.wikipedia.org/wiki/Joint_Test_Action_Group>`_ +* `STM32/gdb/OpenOCD HOWTO <http://fun-tech.se/stm32/OpenOCD/gdb.php>`_ +* STMicro documentation for STM32F103RB microcontroller: + + * `All <http://www.st.com/mcu/devicedocs-STM32F103RB-110.html>`_ + * `Datasheet (pdf) <http://www.st.com/stonline/products/literature/ds/13587.pdf>`_ + * `Reference Manual (pdf) <http://www.st.com/stonline/products/literature/rm/13902.pdf>`_ |