SparkFun Electronics Forum

Is JTAG processor need to develop on SAM7 processors? (it costs more than the eval board!)

Can't one just use the USB for development?

What additional does the JTAG give the developer?

Debugging, as well as programming.

wadcock2 wrote:Is JTAG processor need to develop on SAM7 processors? (it costs more than the eval board!)

Can't one just use the USB for development?

What additional does the JTAG give the developer?

I believe that some or all SAM7's like most ARMs, have a factory-installed bootloader that accepts your compiled/linked code via a serial or USB or I/O mechanism. The I/O type varies; most common are UART and USB.

A JTAG is a super valuable debugging aid, for breakpoints, fast flash loading, etc. Most all professionals use JTAG or the newer equivalents.

For SAM7 the USB bootloader is called SAMBA. It's just a bootloader, though. No debugging.

ARM7 is old news, though. Unless you have a specific reason to use ARM7, you should be using the Cortex-M3 chips.

And they can use two-wire SWD instead of a JTAG connector.

JTAG is the way to go: debug/flash across different vendors without an itch.
Other proprietary debug interface can be more efficient and requires less resources, but they all end up being expensive and lock you to a vendor.

For price, you can DIY a wiggler-like parallel interface (if your PC have one). There is also some low price interface based around FTDI chip (I use one from http://www.embedded-projects.net/ ).

PS: embedded project has also USBProg interface, which can handle AVR/ARM/JTAG, but I do not know this product in detail.

Okay, I get a JTAG. I have a parallel port today, but I don't know about next year's computer. So I'll look for a USB one.

I've seen them, but they'll say tested on xxx, but not on yyy. (put in names like LPC and SAM7) Stevech says they should work on any manufacturer's (ARM) JTAG.

Thanks to all for you input.
Bill

If you can find a used or educational-priced J-Link, it's a good way to go for flashing and sophisticated debugging.

With apologies to SFE...
There are some less expensive flash-write only JTAG things such as
http://www.olimex.com/dev/arm-jtag.html Perhaps all these wiggler-type JTAGs use the parallel port.
http://www.olimex.com/dev/arm-usb-ocd.html
http://www.micro4you.com/store/arm-jtag ... od_90.html

and more. Google is willing to help.

Like mentioned, the J-Link EDU is the best if this is used for non-commercial development. J-Link supports both JTAG and SWD.

Both the Olimex ones above are sold at Sparkfun. The USB one is a standard FT2232 based JTAG.

Whatever you use, its more important that the development environment you are using supports your JTAG programmer.

As for full JTAG debugging, with JTAG and FLASH breakpoints, source debugging, data breakpoints, and so on that pro's use, I think this takes one to IAR or Keil.
I use IAR and wouldn't THINK of doing a fixed priced contract without it and J-Link.

But SFE is more about hobby and edu folks on a tight budget and with more time to devote to creating tools.