So what are these exactly? I'm familiar with PIC and AVR chips and have been working with PIC16's and PIC24's using MC's tools and dev boards. But I constantly see these Basic Stamps, PICaxe, and Parallax chips/pcb's for sale. And when I look at them, most of them look like a small breakout board with a PIC on it. So what are these used for? Are they just pic chips with minor supporting hardware on the board? Are they PIC chips set up to make programming easier for hobbiest? Just wondered why you would use one of these over the MC development stuff. I assume Bruce can answer all this pretty easily.

 

Parallax Inc's Basic Stamps have been around for over a decade.

The Basic Stamps are programmed in a Basic-like language that's comparatively easy to learn. The source code isn't compiled; it's tokenized. The tokenized code is downloaded to an EEprom on the Stamp via a USB or serial port interface.

The Stamps have onboard ROM that's used to interpret the tokenized code into the machine code for the uC, along with onboard clocks, etc.

The Basic Stamp 1 uses a slightly different (and more limited) version of Basic than the Basic Stamp 2 series.

These Basic Stamps are great for an educational environment; where the same uC will be re-used over and over again for different projects. Since the complexities of handling the various uC registers for I/O, timers, etc. are handled by the ROM, the same source code is reasonably portable between the various BS2 stamps. This would not necessarily be the case with a PIC, even within the same class.

The major drawbacks of the Basic Stamps are:
1) Cost. You can purchase a PIC16F887 for under $2. A BS2-P40 will cost about 40x that much. It would be impossible to use a Stamp in a product and have competitive pricing. However, if the same uC will be re-used continually for many projects, the cost can be amortized over many years.

2) Performance. While the onboard oscillator may run at 20 to 50MHz, the program code is interpreted. It takes a lot of machine cycles to look up the code, fetch and execute it. In an academic setting where you may simply be flashing LEDs, putting characters on an LCD, etc. speed is not much of an issue.

3) Size. The Stamps take up a lot of real estate compared to sizes that are available in PIC offerings. This isn't much of an issue on a breadboard.

 

k thanks Sarge. I thought it would be something like that.