Introduction.
This discussion is intended to acquaint the reader with the BASIC Stamp which is a product of Parallax, Inc. .
The discussion is confined to the Basic Stamp 1 (BS1). However, many of the observations may be extended to the more powerful BS2. The intent is to provide you with an idea of the capabilities of this device and provide enough info rmation to get you started at minimum cost. I made a number of errors in over buying a development kit and a carrier board, when, in fact, all that is required is the BS1-IC itself. Thus, hopefully, I can save you the $90 for the development kit and the $15 for the carrier board. You can begin experimenting with the Stamp for the cost of the Stamp itself; $35.00.
The Stamp is a complete BASIC programmable computer mounted on a 14 pin SIP package. Programs are written in a variation of BASIC called PBASIC on your PC and are then downloaded to the Stamp with a single keystroke via the PC's parallel port. On finding the program doesn't work as intended, simply modify the BASIC program and again download. Once satisfied, disconnect the parallel port interface and you have a working circuit. Power it up and it does its thing.
There is no steep learning curve. I had never used the Stamp and assigned two undergraduate students to look at it. Within the day, they had developed an arrangement with eight LEDs that flashed with all kinds of patterns and another which controlled a stepping motor. Within three weeks, I had 26 students controlling bar graph displays via a shift register, acquiring data using an ADC0832, sending serial data to a PC and interfacing with serial EEPROM. Several students went on to also interface with an LCD panel, a Vector 2X compass module and a 200 mV panel meter. Both the students and myself were very excited.
The Stamp relates to a discussion of the parallel port in a number of ways.
First, the parallel port is used in developing Stamp programs via a three conductor cable. Programs are downloaded using the parallel port and the Stamp may be used to display values on the PC's terminal.
But, in addition, I view the parallel port as a development platform in developing applications which will later be implemented using the Stamp. That is, develop the application using the parallel port where you have all of the debugging tools. In my case, this is TurboC Version 2.0. Once you have conquered Murphy's Law at every turn and thoroughly understand your design it is a simple matter to map your design over to the Stamp. Of course, this requires a rewrite of your software in BASIC. I don't know BASIC and really don't want to learn it and my students had forgotten anything they had ever learned. However, we have found that once we have a working design on the parallel port, we can map over to the Stamp within an hour and this includes the redo of the software.
In addition, there are many applications where the parallel port and the Stamp may be used in conjunction with one another. For example, one weakness of the PC is the inability to resolve time with any accuracy better than 18 msecs. Timing is one of the STAMP's strong points. For example, a timing arrangement for a Cub Scout Pinewood Derby competition might consist of a Stamp for each lane to do the start - finish timing. Upon completion of a race, the parallel port might command each Stamp in turn to send it's timing data.
Assembling your Development Tools.
You will of course need a Stamp. Jameco, sells them for $34.95 (Jameco Part Number #127693).
Jameco also sells the BASIC Stamp Programming Package (Jameco #127714) at $89.95. However, I suggest you save your money.
The programming package consists of a cable to interface the parallel port with the Stamp, a program disk and a 172 page manual. Sixty pages are devoted to a discussion of the PBASIC instructions and the balance is application notes. Let's take each of these and see how they may be obtained far more inexpensively.
Cable.
The cable consists of three conductors with a male DB-25 on one end to interface with the parallel port.
Parallel Stamp
Port
Term 25 (GRD) Term 2 (GRD)
Term 11 (BUSY) Term 3 (PCO)
Term 2 (Data_0) Term 4 (PCI)
For solder less bread boarding, we use a three foot 25 conductor ribbon cable with a male DB-25 on one end and a 26 pin female IDC header on the other. This mates with a male header with wire wrap terminals. We widen the spacing of the two rows of wire wrap terminals and plug it into the breadboard, and then simply cross connect to the Stamp. This arrangement is described in the Parallel Port Manual - Vol 1 and we use it in all applications. This cable and the connector are available from me for $10.00.
When we go to a wire wrap version, we attach leads to Stamp terminals 2, 3 and 4 and use clip leads to connect from the 26 pin wire wrap header to the STAMP for any last minute program modifications.
Program and Manual.
Both the program disk and the entire manual are available at;
This file is nominally 720K. After unzipping, you will have both the program disk and the manual in .PDF format.
The manual is contained in two PDF files; bs1book1.pdf and bs1book2.pdf. These may be read and printed using an Acrobat reader. (A free copy of an Acrobat reader is available at
The EXE and TXT files are associated with developing your program and downloading from the PC to the Stamp. There are also numerous examples in the BAS files.
Hopefully, I have saved you a chunk of change. Simply make up the three conductor cable and obtain the ZIP file from the Parallax ftp site.
(This is not to criticize Parallax. In fact, they do an excellent job of promoting and supporting their products and certainly they can't be criticized for offering a developer's kit as this attracts new users. All I am doing is noting that you don't re ally need the kit.)
Prototyping.
Jameco also sells a carrier board (Part #127706) at $14.95. This is a 3.5 inch X 2 inch board with a snap connector for a 9 V transistor battery, a 5V voltage regulator, a small push-button, a 10-pin socket for the Stamp and an area for constructing external circuitry.
Here again, you might consider before you buy. I tend to build on a solder less breadboard before committing to anything of a more permanent nature and you can buy a pretty large solder less breadboard for the same price as the carrier board. Unlike the carrier board, the solder less breadboard may be used again and again.
Figure #1 illustrates my typical prototyping arrangement.
Once I have something that I desire to make more permanent, I break a piece of Vector Board to the appropriate size and use wire wrap. In mounting the Stamp, I use a 20 pin wire wrap DIP IC socket. By the time I have gotten to this point, I am pretty sure the program is firm, and thus I dispense with the 26 pin wire warp header. One can always connect the Stamp to the parallel port using small clips on terminals 2, 3 and 4 if program refinements are required.
Resources.
I don't think I have ever seen a product that is as well supported on the Internet as the Basic Stamp.
A few of the best resources are noted below. From these you will find that you can quickly assemble a list of other resources.
Parallax Homepage -
Parallax ftp Site -
Nuts and Volts Magazine Articles -
List of Stamp Applications -
Microchip Homepage -
e-mail.
In addition Parallax maintains a listserv via e-mail. To subscribe, send e-mail to;
majordomo@parallax.com
In the body of your message type;
SUBSCRIBE
A word of caution. As of this date the number of daily messages is over 50.
Happy Stamping!