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My mbed Is Up

Mon, 11/30/2009 - 2:53pm
Screaming Circuits

I wrote about the new mbed development board a while back and mine just arrived over the holiday weekend. I have to say, true to it's promise, It was the easiest piece of development hardware that I've ever brought up:

  1. Take it out of the shipping box
  2. Plug in the USB cable to the board and my computer
  3. Wait a minute for it to be recognized and open up like a USB thumb drive
  4. Double click on the web shortcut in the drive
  5. Register
  6. Click the Compiler link
  7. Pull up a code sample and modify it a bit (I didn't need to modify it, but I did anyway)
  8. Click the compile button
  9. Save it to the mbed as though it were a USB thumb drive
  10. Press the reset button on the mbed board

That's ten steps, but it's only ten steps. There was nothing else to do. Nothing. The longest step was number seven which took me about two minutes. I programmed a "Knight Rider" sweeper with the four on-board LEDs. I made one of those for my Jack-o-lantern back at Halloween, so it was the first test program that popped into my head.

I built the Jack-o-lantern sweeper with eight LEDs and an 8 bit PIC16F819. The PIC I used came in an 18 pin thru-hole DIP package, costing $3.22 at Digi-Key, and I hand soldered it all on an old perf board. It runs at 20MHz, has 16 GPIO, 3.5K program code space, 256 bytes of FLASH and 256 bytes of RAM.

Mbed pinout The 32 bit NXP LPC1764 runs at 100MHz in a 100 pin LQFP and costs $8.70 in quantity of one at Digi-Key. (The dev board, of course, costs more then that) It has 512K of program FLASH and 64K of RAM. The dev board can have up to 25 GPIO (the chip can have up to 70 GPIO with your hardware) along with the standard assortment of peripherals that can be configured, including six hardware PWM channels. The mbed dev board is like a breakout board configured as a 40 pin 0.1" DIP so it will be easy to prototype with.

The processor, being a fine-pitch package really isn't hand-solderable like the PIC except for by the most adventurous of folks, but that's where Screaming Circuits comes in. Why wait for your custom hardware before starting on the software. Get one of these mbed dev boards to work on your software while the EE folks are designing the custom hardware. Then, when they're done, we'll assemble up the prototypes and you can integrate it all together. Take some time out of your development schedule that way.

I've wanted to try out an ARM processor for quite a while, but prior to this, haven't found the right way to do so while keeping within the limits of my time availability and skill set, but this looks like it could very well do the job.

Duane Benson

Robots rule!

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