NOTE: Free essay sample provided on this page should be used for references or sample purposes only. The sample essay is available to anyone, so any direct quoting without mentioning the source will be considered plagiarism by schools, colleges and universities that use plagiarism detection software. To get a completely brand-new, plagiarism-free essay, please use our essay writing service.
One click instant price quote
... write serial data on an output pin sound - send a sound of a specific frequency to an output pin toggle - toggle the bit on an output pin Instructions specific to the BASIC Stamp: branch - read a branching table debug - send a debugging string to the console on the desktop computer eeprom - download a program to EEPROM look down - return the index of a value in a list lookup - array lookup using an index nap - sleep for a short time pause - delay for the specified time random - pick a random number read - read a value from EEPROM sleep - power down for the specified time write - write data to EEPROM Operations: + - addition - - subtraction - multiplication (low-word) - multiplication (high-word) / - division // - mod max - return maximum of 2 values min - return minimum of 2 values & - AND | - OR ^ - XOR & / - NAND |/ - NOR ^/ - XNOR If statement logic: = < > < < = > > = AND OR Variables All variables in the BS- 1 have pre-defined names (which you can substitute with names of your own). Remember that there are only 14 bytes of RAM available, so variables are precious. Here are the standard names 16 -bit word variable 13 - 8 -bit byte variables bit 0, bit 1, bit 2...
bit 15 - 1 -bit bit variables Because there are only 14 bytes of memory, w 0 and b 0 /b 1 are the same locations in RAM, and w 1 and b 2 /b 3 are the same, and so on. Also, bit 0 through bit 15 reside in w 0 (and therefore b 0 /b 1 as well). I/O pins You can see that 14 of the instructions in the BS- 1 have to do with the I/O pins. The reason for this emphasis is the fact that the I/O pins are the only way for the BASIC Stamp to talk to the world. There are eight pins on the BS- 1 (numbered 0 to 7) and 16 pins on the BS- 2 (numbered 0 to 15). The pins are bi-directional, meaning that you can read input values on them or send output values to them.
The easiest way to send a value to a pin is to use the HIGH or LOW functions. The statement high 3 sends a 1 (+ 5 volts) out on pin 3. LOW sends a 0 (Ground). Pin 3 was chosen arbitrarily here -- you can send bits out on any pin from 0 to 7. There are a number of interesting I/O pin instructions. For example, POT reads the setting on a potentiometer (variable resistor) if you wire it up with a capacitor as the POT instruction expects.
The PWM instruction sends out pulse-width modulated signals. Instructions like these can make it a lot easier to attach controls and motors to the Stamp. See the documentation for the language for details. Also, a book like Scott Edward's Programming and Customizing the BASIC Stamp Computer can be extremely helpful because of the example projects it contains. Playing with a BASIC Stamp If you would like to play with a BASIC Stamp, it's very easy to get started. What you need is a desktop computer and a BASIC Stamp starter kit.
The starter kit includes the Stamp, a programming cable and an application that you run on your desktop computer to download BASIC programs into the Stamp. You can get a starter kit either from Parallax (the manufacturer) or from a supplier like Jameco (who should be familiar to you from the electronic gates and digital clock articles). From Parallax, you can order the BASIC Stamp D Starter Kit (part number 27202), or from Jameco you can order part number 140089. You will receive the Stamp (pictured below), a programming cable, software and instructions. The kit is $ 79 from both suppliers. Occasionally, Parallax runs a special called "We " ve Bagged the Basics" that also includes Scott Edward's Programming and Customizing the BASIC Stamp Computer.
Hooking up the Stamp is easy. You connect it into the parallel port of your PC. Then you run a DOS application to edit your BASIC program and download it to the Stamp. Here is a screenshot of a typical editor (in this case, the one from Scott Edward's book): To run the program in this editor, you hit ALT-R. The editor application checks the BASIC program and then sends it down the wire to the EEPROM on the Stamp. The Stamp then executes the program.
In this case, the program produces a square wave on I/O pin 3. If you hook up a logic probe or LED to pin 3 (see the electronic gates article for details), you will see the LED flash on and off twice per second (it changes state every 250 milliseconds because of the PAUSE commands). This program would run for several weeks off of a 9 -volt battery. You could save power by shortening the time that the LED is "on" (perhaps it is on for 50 milliseconds and off for 450 milliseconds), and also by using the NAP instruction instead of PAUSE. Creating a Really Expensive Digital Clock Spending $ 79 to flash an LED may seem extravagant to you.
What you would probably like to do is create something useful with your BASIC stamp. By spending about $ 100 more you can create a really nice digital clock! This may seem extremely extravagant, until you realize that the parts are reusable in a variety of other projects that you may want to build later. Let's say that we would like to use the I/O pins on the BASIC Stamp to display numeric values.
In the digital clock article, we saw how to interface to a 7 -segment LED display using a 7447 chip. 7447 s would work just as well with the BASIC Stamp. You could wire four of the I/O pins straight into a 7447 and easily display a number between 0 and 9. Since the BS- 1 Stamp has eight I/O pins, it is easy to drive two 7447 s directly like this. For a clock, we need a minimum of four digits. To drive four 7447 s with eight I/O pins, we have to be slightly more creative. The following diagram shows you one approach: In this diagram, the eight I/O lines from the Stamp enter from the left.
This approach uses four lines that run to all four 7447 s. Then the other four lines from the Stamp activate the 7447 s in sequence ("E" on the chips means "Enable" -- on a 7447, that would be the blanking input on pin 5). To make this arrangement work, the BASIC program in the Stamp would output the first digit on the four data lines and activate the first 7447 by toggling its E pin with the first control line. Then it would send out the value for the second digit and activate the second 7447, sequencing through all four of the 7447 s like this repeatedly. By wiring things slightly differently, you could actually do this with only one 7447. By using a 74154 de multiplexer chip and some drivers, you could drive up to 16 digits using this approach.
This is, in fact, a standard way to control LED displays. For example, if you have an old LED calculator, turn it on and shake it while watching the display. You will actually be able to see that only one digit is ever illuminated at once. The approach is called multiplexing the display. While this approach works fine for clocks and calculators, it has two important problems: LEDs consume a lot of power. 7 -segment LEDs can only display numeric values. An alternative approach is to use an LCD screen.
As it turns out, LCDs are widely available and can be easily hooked to a Stamp. For example, the two-line by 16 -character alphanumeric display shown below is available from both Jameco (part number 150990) and Parallax (part number 27910). A typical display is shown here, mounted on a breadboard for easier interfacing: This sort of LCD has several advantages: The display can be driven by a single I/O pin. The display contains logic that lets a Stamp communicate with it serially, so only one I/O pin is needed.
In addition, the SEROUT command in Stamp BASIC handles serial communication easily, so talking to the display is simple. The LCD can display alphanumeric text: letters, numbers and even custom characters. The LCD consumes very little power -- only 3 milliards. The only problem is that one of these displays costs $ 59. Obviously, you would not embed one of these in a toaster oven. If you were designing a toaster oven, however, you would likely prototype with one of these displays and then create custom chips and software to drive much cheaper LCDs in the final product.
To drive a display like this, you simply supply it with + 5 volts and ground (the Stamp supplies both from the 9 -volt battery) and then hook one of the I/O pins from the Stamp to the display's input line. The easiest way I have found to connect the Stamp's I/O pins to a device like an LCD is to use a wire-wrap tool (Jameco part number 34577) and 30 -gauge wire wrap wire (Jameco part number 22541 is typical). That way, no soldering is involved and the connections are compact and reliable. The following BASIC program will cause a BASIC Stamp to behave like a clock and output the time on the LCD (assuming the LCD is connected to I/O pin 0 on the Stamp): pause 1000 'wait for LCD display to boot serious 0, n 2400, (254, 1) 'clear the display serious 0, n 2400, ("time: ") 'Paint "time: " on the display 'preset before loading program b 0 = 0 'seconds b 1 = 27 'minutes b 2 = 6 'hours again: b 0 = b 0 + 1 'increment seconds if b 0 < 60 then minutes b 0 = 0 'if seconds = 60 b 1 = b 1 + 1 ' then increment minutes minutes: if b 1 < 60 then hours b 1 = 0 'if minutes = 60 b 2 = b 2 + 1 ' then increment hours hours: if b 2 < 13 then show b 2 = 1 'if hours = 13 reset to 1 show: serious 0, n 2400, (254, 135) 'position cursor on display, 'then display time serious 0, n 2400, (#b 2, ": ", #b 1, ": ", #b 0, ") pause 950 'pause 950 milliseconds goto again 'repeat In this program, the SEROUT commands send data to the LCD. The sequence (254, 1) clears the LCD (254 is the escape character and 1 is the command to clear the screen). The sequence (254, 135) positions the cursor.
The other two SEROUT commands simply send text strings to the display. This approach will create a reasonably accurate clock. By tweaking the PAUSE statement you can get the accuracy to within a few seconds a day. Obviously, in a real clock you would like to wire up a push-button or two to make setting it easier -- in this program, you preset the time before you download the program to the Stamp. While this approach is simple and works, it is not incredibly accurate. If you want better accuracy, one good approach would be to wire a real-time clock chip up to your Stamp.
Then, every second or so, you can read the time from the chip and display it. A real-time clock chip uses a quartz crystal to give it excellent accuracy. Clock chips also usually contain date information and handle leap year correction automatically. One easy way to interface a real-time clock to a stamp is to use a component called the Pocket Watch B. Pocket Watch B Module The Pocket Watch B is available from both Jameco (part number 145630) and Parallax (part number 27962). This part is about as big as a quarter and contains the clock chip, crystal and a serial interface so that only one I/O pin is necessary to communicate with it.
This component costs about $ 30 -- again, not something you want to embed in a toaster oven, but easy to play with when constructing prototypes.
Free research essays on topics related to: real time, b 2, stamp, b 1, four lines
Research essay sample on Four Lines Real Time
