SimpleJTAG is an JTAG/SWD adapter protocol designed to be easy implementable
on (almost) any hardware, targeting first of all low-cost and open-hardware
development boards like Arduino and MSP430 Launchpad.

SimpleJTAG is expected to provide several levels of protocol, offering
different ratio of ease of firmware development vs target access speed.
Currently, "level 0" protocol is defined, which uses the simplest possible
bitbanging protol, where each signal transition is driven by host. It is also
half-duplex, following request-response pattern for each command. So, it
is slow, but at the same time, can be implemented even on the simplest
MCUs, with minimum flash space, and with bitbang UART implementation for
connection to host.

This project provides MCU and board independent implementation of protocol
developed using Peripheral Template Library (PTL)
(https://github.com/pfalcon/PeripheralTemplateLibrary).

To build firmware, make sure that you have submodules initialized:

git submodule update

You will need gcc toolchain for your target architecture (msp430-gcc,
avr-gcc, arm-gcc), etc. To flash compiled firmware, you will need
one of the flash tools for your platform/board. See PTL documentation
at the link above for more details on development environment setup.

You can build firmware for a particular sub-architecture using:

make TARGET=msp430

Besides msp430, you can use avr, stm32, efm32, etc. See PTL
documentation and makefiles for further details.

OpenOCD with corresponding driver can be found at
https://github.com/pfalcon/openocd/tree/simplejtag . To use it:

git clone https://github.com/pfalcon/openocd openocd-simplejtag
cd openocd-simplejtag
git checkout simplejtag
./configure --enable-simplejtag
make

Then use following openocd.cfg:
-------------
interface simplejtag_l0
simplejtag_l0 port /dev/ttyACM0
-------------


WARNING AND DISCLAIMER
Before connecting any other device to your board serving as a JTAG
adapter, always consider difference in their voltage raiting - they
should be compatible. Most of devices nowadays are powered by at most
3.3V. Original AVR-based Arduino boards use legacy voltage of 5V.
Using original Arduino will burn a device connected to it. There are
reingeneered Arduino clones with ability to use contemporary 3.3V
voltage. Note that there are devices which use even lower supply
voltages.

If in doubt, always consider that supply voltage, galvanic isolation,
etc. are what differs professional $100+ adapter from using a low-cost
board as such.

Remember that SimpleJTAG (just as any other open-source software and
hardware) comes without warranty of any kind and you use it at your
own risk.