The Microcontroller Idea Book - Jan Axelson's Lakeview Research

More documents

Recommendations

Info

Chapter 8 Table 8-1. The forward voltage drop across an LED varies with the color. LED color typical forward voltage (volts) Table 8-1 shows typical forward voltages for different colors of LEDs. Typical LED operating currents are between 10 and 20 milliamperes. For a bright display with low power consumption, look for types labeled high efficiency. One disadvantage to LEDs is that the light from most is hard to detect in bright light, especially outdoors. A tinted, transparent sheet of plastic mounted over the display can make it more visible in bright light. For red LEDs, transparent red or purple works well. For best visibility over a wide area, look for LEDs with a wide viewing angle. This means that the LED emits light in a wide cone, so you don’t need to view it straight-on. LED Interfaces Red 1.6 Green 2.0 Yellow 2.0 Blue 3.2 Figure 8-1 shows examples of LED interfaces to output ports in an 8052-BASIC system. The outputs of the 80(C)52 and 82(C)55 can’t provide enough current to drive an LED directly. But you can drive an LED with a 74LS374 or 74HC374 latch (A, B), or with a buffer or inverter driven by any output port (C, D). With LSTTL drivers, you should design your circuit so that a low output turns on the LED, since LSTTL outputs can sink more current than they can source. With HCMOS or HCTMOS outputs, either a high or low output can turn on the LED. Use a series resistor to limit the current through the LED. For a brighter display, decrease the value of the resistor. Most LEDs can handle 20 milliamperes of continuous current. You can measure the current directly by connecting an ammeter in series with the LED and resistor. Or, you can calculate the current by measuring the the voltage across the series resistor and dividing it by the resistor’s value. For example, 2.25V/150 ohms = 0.015 amperes, or 15 milliamperes. Both LSTTL and HCMOS devices are capable of 20-milliampere output currents. At these higher currents, the output voltage isn’t specified, but should be enough to light an LED. To turn on an LED at a port, write a 1 or 0, as appropriate, to the bit that controls it, as described in Chapter 6. Listing 8-1 assumes that you have eight LEDs connected to the 126 The Microcontroller Idea Book
Displays Figure 8-1. LED interfaces to output ports. Use an HCMOS output if you want a high output to turn on the LED. Use either HCMOS or LSTTL if you want a low output to turn on the LED. The Microcontroller Idea Book 127
Page 1 and 2:
The Microcontroller Idea Book Circu
Page 3 and 4:
Table of Contents Chapter 1 Microco
Page 5 and 6:
Chapter 11 Control Circuits 185 Swi
Page 7 and 8:
Introduction Introduction This book
Page 9 and 10:
A chapter on assembly-language inte
Page 11 and 12:
Microcontroller Basics 1 Microcontr
Page 13 and 14:
But along with cheap, powerful, and
Page 15 and 16:
makes sense. For simpler designs, a
Page 17 and 18:
Microcontroller Basics Several tech
Page 19 and 20:
Interpreters and compilers are two
Page 21 and 22:
Inside the 8052-BASIC 2 Inside the
Page 23 and 24:
Inside the 8052-BASIC • You can a
Page 25 and 26:
hardware manuals. For programming,
Page 27 and 28:
Inside the 8052-BASIC Figure 2-2 Pi
Page 29 and 30:
Inside the 8052-BASIC Table 2-2. (p
Page 31 and 32:
Inside the 8052-BASIC Code and data
Page 33 and 34:
Powering Up 3 Powering Up This chap
Page 35 and 36:
Powering Up Table 3-1. Parts list f
Page 37 and 38:
Powering Up Figure 3-2. Truth table
Page 39 and 40:
Powering Up Jumper J3 chooses the c
Page 41 and 42:
Powering Up Figure 3-3. This is the
Page 43 and 44:
Powering Up Construction Tips These
Page 45 and 46:
Powering Up Serial Connectors Conne
Page 47 and 48:
You’re now ready to power up the
Page 49 and 50:
Powering Up PRINT XTAL Line Editing
Page 51 and 52:
Powering Up PORT 1 Bit Values: Bit
Page 53 and 54:
Powering Up Listing 3-3. Allows use
Page 55 and 56:
10 CLOCK 1:TIME=0:SEC=0 20 A=0 30 P
Page 57 and 58:
Saving Programs 4 Saving Programs I
Page 59 and 60:
guaranteed for at least ten years.
Page 61 and 62:
Saving Programs Figure 4-3. Circuit
Page 63 and 64:
Jumper J4 is optional. It enables y
Page 65 and 66:
memory on bootup. This is what allo
Page 67 and 68:
This is the recommended algorithm f
Page 69 and 70:
Saving Programs Figure 4-5. Additio
Page 71 and 72:
problems with EPROMs that have a 10
Page 73 and 74:
supply. The chip requires an additi
Page 75 and 76:
Programming 5 Programming When you
Page 77 and 78:
Subroutines have two advantages. Fi
Page 79 and 80:
Programming • Hexadecimal numbers
Page 81 and 82:
Programming It can be hard to find
Page 83 and 84:
Programming Math Operators = + - *
Page 85 and 86: Programming expression / expression
Page 87 and 88: Programming DO: [program statements
Page 89 and 90: Programming LOG(expression) Returns
Page 91 and 92: Programming PH0.@ Same as PRINT@, b
Page 93 and 94: Programming RCAP2 Retrieves or assi
Page 95 and 96: Programming PRINT TAB(2) “hello
Page 97 and 98: Inputs and Outputs 6 Inputs and Out
Page 99 and 100: Unassigned space remains in the mem
Page 101 and 102: U11 is a 74HCT138 3-to-8-line decod
Page 103 and 104: If you wish, you can wire U14’s i
Page 105 and 106: Inputs and Outputs Figure 6-4. Outp
Page 107 and 108: Inputs and Outputs Listing 6-2. Set
Page 109 and 110: The 82C55 also has CMOS-compatible
Page 111 and 112: Inputs and Outputs Pin Symbol Input
Page 113 and 114: Inputs and Outputs An 8255 Interfac
Page 115 and 116: Inputs and Outputs XBY(0FC03h)=9BH
Page 117 and 118: To set or clear a different bit, de
Page 119 and 120: Switches and Keypads 7 Switches and
Page 121 and 122: Switches and Keypads Figure 7-2. Us
Page 123 and 124: exact value depending on the switch
Page 125 and 126: Switches and Keypads Figure 7-4. Tw
Page 127 and 128: Switches and Keypads Figure 7-6. A
Page 129 and 130: Switches and Keypads Custom Keypads
Page 131 and 132: Switches and Keypads • A single c
Page 133 and 134: Switches and Keypads Listing 7-3. T
Page 135: Displays 8 Displays In addition to
Page 139 and 140: Displays Figure 8-2. Ways to connec
Page 141 and 142: Displays Figure 8-4. Four output po
Page 143 and 144: Displays Figure 8-5. The ICM7218D c
Page 145 and 146: In Figure 8-5’s circuit, an 82(C)
Page 147 and 148: Displays Figure 8-7. With the TC721
Page 149 and 150: Displays Figure 8-8. With a charact
Page 151 and 152: Table 8-1. LCD modules containing t
Page 153 and 154: Each character in the CG ROM and CG
Page 155 and 156: Displays Interfacing Full control o
Page 157 and 158: Displays Listing 8-4 (page 2 0f 2).
Page 159 and 160: Displays Listing 8-5. Displays key
Page 161 and 162: Displays Listing 8-6 (page 2 of 2).
Page 163 and 164: Using Sensors to Detect and Measure
Page 165 and 166: • What power supplies are availab
Page 171 and 172: different ground symbols for the tw
Page 173 and 174: 10 REM use single-ended mode 20 REM
Page 181 and 182: Clocks and Calendars 10 Clocks and
Page 183 and 184: Listing 10-1. Uses BASIC-52’s rea
Page 185 and 186: Clocks and Calendars Figure 10-1. P
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 205 and 206:
Page 207 and 208:
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 and 226:
In the infrared link, the amount of
Page 227 and 228:
Calling Assembly-language Routines
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:
Page 241 and 242:
Page 243 and 244:
• BASIC-52’s ON EX1 instruction
Page 245 and 246:
Page 247 and 248:
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
Page 277 and 278:
Page 279 and 280:
Page 281 and 282:
Number Systems Appendix C Number Sy
Page 283 and 284:
Number Systems This table shows the
Page 285 and 286:
Index Index A ADC, 158 - 169 addres
Page 287 and 288:
Index S sample and hold, 169 SBC, 3
show all

The Microcontroller Idea Book - Jan Axelson's Lakeview Research

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?