jtag
Althougth I never used one, I know JTAG is a standardized way to program and debug MCUs. But I see a lot of JTAG from various companies. Can I use a particular JTAG to program/debug MCUs from different companies and with diferent architectures?
For example: can I use a JTAG to program/debug STM32 and LPC micros? (all Cortex-m3) Can I use the same JTAG to program/debug MSP430 micros? (16bit MCU from TI)
Which JTAG do you recommend to buy? And why?
About the JTAG, you don't need a proprietary one, unless the board you have has a proprietary connector. Even then, if you can discover its pinout you could make an adapter connector. The main difference between open/free JTAG projects and a commercial product is that the later will probably have higher speeds, which makes a big difference depending on the complexity of the programs. There are cheap commercial JTAG adapters that are parallel/serial, and somewhat more expensive ones that are USB; given the choice, I'd always prefer USB.
About the toolchain, it's perfectly possible to use GNU tools, (take a look at gnuarm.com) but the downside is that you have to find documentation about how to interface with the device-specific hardware; also you may have to prepare a specific link script for the memory map of your device. The more rare/exotic it is, the less probable it is that you'll find a script already made. And these link scripts can be pretty complicated. If you use a commercial toolchain specifically tailored for your device, you'll find everything already set to make it work on the device.
I'd also recommend to buy a dev board (like this one) for that MCU; It'll be a lot easier to make everything work if you can divide-and-conquer. And having a tested, functional board is the best way to keep software and hardware problems separated.
This is the official ARM Cortex JTAG/SWD connector diagram:
You should follow the data sheet/user manual about any resistors that are required. SWD pins on other LPC chips are usually pulled up internally.
The LPCXpresso IDE might be defaulting to the SWD interface. You need to select the JTAG interface, which is probably what the LPC4337 uses initially.
Best Answer
At its very basic level, JTAG is a standardized serial protocol. You can build one out of a handful of components for under $20, but it will be slow. Generally speaking the more expensive ones offer higher speed, broader voltage support and even autonomous operation. The software used to drive the particular JTAG interface determines whether you will be able to program the devices you are interested in.
Personally I am happy with the $70ish dollar Olimex JTAG units. They are USB, based on the FT2232, work with 5V and 3.3V devices and have good support for both Linux and Windows (I'm not sure about OSX). I also have an Atmel USB Blaster for programming Altera FPGAs (supports down to 1.0V IO) and an older USB based one for Xilinx devices. Finally, I also have a GNICE+ JTAG adapter used primarily for Analog Devices Blackfin processors.
I have not tried it, but I believe that the Altera USB Blaster should work for anything I connect to, although it does not support RTCK (return clock) support. It is primiarly ARM devices which support RTCK, which is a means for the JTAG interface to detect how fast the JTAG clock can go and still be reliable.
My suggestion is to take a look at the particular devices you wish to use and see if you can find a common JTAG unit that is well supported by all.