Sunday, February 10, 2013

Texas Instruments Stellaris LaunchPad - LXAF120H (UPDATED)

Stellaris LaunchPad

You're looking at my latest digital gizmo, an ARM-based Stellaris LaunchPad development board. At the heart of the board is an LX ARM Cortex-M4 32-bit CPU running at a modest (by today's standards) 80MHz. It comes along with 256K of FLASH and 32KB of SRAM. It won't run Linux or Android or any other major operating system, but for writing executives, interrupt handlers and I/O manipulators in C or assembler down at the bare silicon, it has more than enough raw computational power.

I started my professional life nearly 40 years ago by building embedded systems with the 8-bit MOS Technologies 6502 and Zilog Z80. In both those instances the embedded systems had a lot less RAM and EPROM and I was very glad to have them running at a then-blistering 1 to 4MHz.

The  also comes along with a lot of hardware-based timers and very flexible I/O pins. It is, for an old hacker like me, something of a dream come true.

And I got it all for free from an old friend who had in turn gotten it for free from Texas Instruments.

This is a re-re-kickoff of my robotics side of my life. I am moving all the original postings from beebot and putting them here, then decommissioning that web site. I have enough going on writing for this site and Matthew Robertson's review site. Trying to write for three is at least one too many.

So be prepared. The next five posts are being copied over. They were original written around 2006. From this point forward I'll be writing about my embedded adventures (including hobby robotics) on this blog.

Update 11 February

Jim Smith is my friend and fellow computer engineer that I've known since I first met in in 1986. It was Jim who gave me the Stellaris. He sent me an email to today that cleared up a few points.
  • The boards were not free from TI. They had a pre-release order special at half price and with shipping, two were ordered. The regular price of the Stellaris is $12.99 ea, so they were practically free. Jim gave me one of the two he'd ordered for that special price.
  • The ARM is being used to replace an 80c196-based 16-bit embedded system with a fixed 64K of RAM and EPROM. The 12-MHz 80c196 executes about 1.5 million instructions/sec. The 80MHz chip has roughly one MIP/MHz, or 80 MIPs by comparison. The LXAF120H also has built-in serial and digital I/O, replacing even more older hardware in the form of individual chips.
So, even if the Stellaris isn't completely free, it's pretty dog-gone cheap.

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