The Microcontroller Idea Book - Jan Axelson's Lakeview Research

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Chapter 12 Some IREDs are manufactured with integral lenses that focus the output into a beam. For example, Harris’ F5D1 and F5E1 IREDs are identical, except that the F5D1 has a lens that aims the energy in a narrow beam, while the F5E1 has a flat window and wider beam angle. An IRED with an integral lens is an easy, low-cost option, if it can do the job. A flat-window package is useful if you want to add an external lens, or if you want a wider beam, to reach multiple receivers around a room, for example. If you’re interested in experimenting with lenses, Edmund Scientific has a huge selection, including inexpensive educational-grade lenses, lens mounts, optical benches, and books on optics. Although infrared links are most often thought of as line-of-sight paths—for transmitting across a room, for example—optics can also overcome this limitation. For example, with mirrors, you can transmit around corners. Radio Links Another possibility for wireless links is to use radio frequencies. Radio transmissions consist of high-frequency electromagnetic waves that travel through the atmosphere. Most radio waves will also pass through windows, walls, and other solid objects. This makes radio useful where a direct line-of-sight between transmitter and receiver isn’t available. Radio can also be a good choice for outdoor links, where daylight may interfere with infrared transmissions and wired links are inconvenient. Radio circuits require special construction techniques, and radio transmissions must not violate regulations of agencies such as the Federal Communications Commission (FCC). For these reasons, the easiest option is to buy the transmitters and receivers for your link, rather than build them yourself. One source of low-cost radio-frequency transmitter and receiver circuits is Electronics 123. The links transmit in the range 300-315 Megahertz, a frequency band used by many garage-door openers and alarm systems. The boards come with complete schematics and instructions for use. The circuits are similar to the infrared-transmitting circuits described earlier. The transmitter sends 4-bit codes to a receiver identified by an 8-bit address. The transmitter and receiver use Holtek’s HT-12E encoder and HT-12D or HT-12F decoder chips, also available separately from Electronics 123 and Digi-Key. The chips are similar in operation to Motorola’s 146026/7 encoder and decoder, and you can in fact use them in infrared links as well. The encoder and decoder each require just one resistor to set the oscillator frequency. 216 The Microcontroller Idea Book
Calling Assembly-language Routines 13 Calling Assembly-language Routines Although BASIC-52 is a convenient programming language that can do a lot, sometimes it’s just not fast enough for what you need. A line in a BASIC-52 program can take many milliseconds to execute, and for some applications, this is just too long. One way to speed things up is to use assembly language. This doesn’t mean that you have to give up on BASIC-52 entirely. You can continue to use it for the parts of your programs that aren’t time-critical, and call assembly-language routines only for those parts that have to be fast. BASIC-52 can also serve as a convenient development system for loading and testing assembly-language routines in RAM, and even for programming the routines into NV memory. Calling routines from BASIC-52 is a good way to become familiar with assembly-language programming. Plus, through experimenting, you can learn a lot about the internal workings of the 8052 chip and how the BASIC-52 interpreter works. This chapter explores how and when to interface assembly-language routines to BASIC-52 programs. An example project connects a digital-to-analog converter to the 8052-BASIC. Programs in BASIC-52 and assembly language cause a sine wave to appear at the converter’s output. There’s also a section on how to use your BASIC-52 system as a general-purpose The Microcontroller Idea Book 217
Page 1 and 2:
The Microcontroller Idea Book Circu
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Table of Contents Chapter 1 Microco
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Chapter 11 Control Circuits 185 Swi
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Introduction Introduction This book
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A chapter on assembly-language inte
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Microcontroller Basics 1 Microcontr
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But along with cheap, powerful, and
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makes sense. For simpler designs, a
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Microcontroller Basics Several tech
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Interpreters and compilers are two
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Inside the 8052-BASIC 2 Inside the
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Inside the 8052-BASIC • You can a
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hardware manuals. For programming,
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Inside the 8052-BASIC Figure 2-2 Pi
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Inside the 8052-BASIC Table 2-2. (p
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Inside the 8052-BASIC Code and data
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Powering Up 3 Powering Up This chap
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Powering Up Table 3-1. Parts list f
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Powering Up Figure 3-2. Truth table
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Powering Up Jumper J3 chooses the c
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Powering Up Figure 3-3. This is the
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Powering Up Construction Tips These
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Powering Up Serial Connectors Conne
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You’re now ready to power up the
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Powering Up PRINT XTAL Line Editing
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Powering Up PORT 1 Bit Values: Bit
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Powering Up Listing 3-3. Allows use
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10 CLOCK 1:TIME=0:SEC=0 20 A=0 30 P
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Saving Programs 4 Saving Programs I
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guaranteed for at least ten years.
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Saving Programs Figure 4-3. Circuit
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Jumper J4 is optional. It enables y
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memory on bootup. This is what allo
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This is the recommended algorithm f
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Saving Programs Figure 4-5. Additio
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problems with EPROMs that have a 10
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supply. The chip requires an additi
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Programming 5 Programming When you
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Subroutines have two advantages. Fi
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Programming • Hexadecimal numbers
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Programming It can be hard to find
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Programming Math Operators = + - *
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Programming expression / expression
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Programming DO: [program statements
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Programming LOG(expression) Returns
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Programming PH0.@ Same as PRINT@, b
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Programming RCAP2 Retrieves or assi
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Programming PRINT TAB(2) “hello
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Inputs and Outputs 6 Inputs and Out
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Unassigned space remains in the mem
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U11 is a 74HCT138 3-to-8-line decod
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If you wish, you can wire U14’s i
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Inputs and Outputs Figure 6-4. Outp
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Inputs and Outputs Listing 6-2. Set
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The 82C55 also has CMOS-compatible
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Inputs and Outputs Pin Symbol Input
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Inputs and Outputs An 8255 Interfac
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Inputs and Outputs XBY(0FC03h)=9BH
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To set or clear a different bit, de
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Switches and Keypads 7 Switches and
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Switches and Keypads Figure 7-2. Us
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exact value depending on the switch
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Switches and Keypads Figure 7-4. Tw
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Switches and Keypads Figure 7-6. A
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Switches and Keypads Custom Keypads
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Switches and Keypads • A single c
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Switches and Keypads Listing 7-3. T
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Displays 8 Displays In addition to
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Displays Figure 8-1. LED interfaces
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Displays Figure 8-2. Ways to connec
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Displays Figure 8-4. Four output po
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Displays Figure 8-5. The ICM7218D c
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In Figure 8-5’s circuit, an 82(C)
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Displays Figure 8-7. With the TC721
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Displays Figure 8-8. With a charact
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Table 8-1. LCD modules containing t
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Each character in the CG ROM and CG
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Displays Interfacing Full control o
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Displays Listing 8-4 (page 2 0f 2).
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Displays Listing 8-5. Displays key
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Displays Listing 8-6 (page 2 of 2).
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Using Sensors to Detect and Measure
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• What power supplies are availab
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different ground symbols for the tw
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10 REM use single-ended mode 20 REM
Page 175 and 176: Using Sensors to Detect and Measure
Page 181 and 182: Clocks and Calendars 10 Clocks and
Page 183 and 184: Listing 10-1. Uses BASIC-52’s rea
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Page 187 and 188: Clocks and Calendars Table 10-1. Re
Page 189 and 190: If you want an alarm frequency othe
Page 191 and 192: Clocks and Calendars Listing 10-3 (
Page 193 and 194: Clocks and Calendars Listing 10-3 (
Page 195 and 196: Control Circuits 11 Control Circuit
Page 197 and 198: the LSTTL part, and wire the desire
Page 199 and 200: Control Circuits Listing 11-1. Cont
Page 201 and 202: Control Circuits Listing 11-2. Demo
Page 203 and 204: Control Circuits disables the outpu
Page 209 and 210: Wireless Links 12 Wireless Links Wi
Page 211 and 212: Wireless Links Figure 12-2. This in
Page 213 and 214: Wireless Links Because there are th
Page 215 and 216: Wireless Links Figure 12-4. The GP1
Page 217 and 218: through the LEDs. If you prefer an
Page 219 and 220: Wireless Links Figure 12-6. Using a
Page 221 and 222: Wireless Links Figure 12-7. Using a
Page 223 and 224: Wireless Links IREDs emit energy at
Page 225: In the infrared link, the amount of
Page 229 and 230: into memory in the 8052-BASIC syste
Page 231 and 232: 2048h in code memory. This is becau
Page 233 and 234: Binary value 1100 0101 Hex equivale
Page 235 and 236: Successful assembly is a good sign,
Page 237 and 238: statement must match the address in
Page 239 and 240: Calling Assembly-language Routines
Page 243 and 244: • BASIC-52’s ON EX1 instruction
Page 249 and 250: Running BASIC-52 from External Memo
Page 251 and 252: 14-1 for longer delays between writ
Page 253 and 254: In Figure 3-1, tie pin 31 of U2 (EA
Page 255 and 256: Related Products 15 Related Product
Page 257 and 258: Finally, a compiled BASIC program u
Page 259 and 260: Related Products Figure 15-3. Blue
Page 261 and 262: Sources Appendix A Sources This App
Page 263 and 264: Programming and Interfacing the 805
Page 265 and 266: Sources Product Vendors The followi
Page 267 and 268: Sources Electronics 123 17921 Rowla
Page 269 and 270: Sources Micro Future 40944 Cascado
Page 271 and 272: Sources Siemens Components 2191 Lau
Page 273 and 274: Programs for Loading Files Appendix
Page 275 and 276: Programs for Loading Files Listing
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Programs for Loading Files Listing
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Programs for Loading Files Listing
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Number Systems Appendix C Number Sy
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Number Systems This table shows the
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Index Index A ADC, 158 - 169 addres
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Index S sample and hold, 169 SBC, 3
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