The Microcontroller Idea Book - Jan Axelson's Lakeview Research

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Chapter 11 Figure 11-4. The UCN5804B makes it easy to control the speed, direction, and operating mode of a stepper motor. 8052-BASIC to do other things, without having to worry about generating the signals to control each step of the rotation. The circuit uses a UCN5804B stepper-motor translator/driver (U5) from Allegro Microsystems (formerly Sprague). The chip automatically creates the drive signals for operation in any of three modes. U3 is a 4066B CMOS quad switch that enables you to select any of 15 speeds. U4 is a 555 timer that outputs a square wave in proportion to the selected speed. U5 uses the square wave to time the steps. U5 has four outputs that can sink up to 1.5 ampere each, and can sustain up to 35 volts. The chip includes diodes that protect against inductive transients, and thermal protection that 192 The Microcontroller Idea Book
Control Circuits disables the outputs if the chip begins to overheat. For high output currents, use a slide-on DIP heat sink to prevent overheating. The motor is a 4-phase, unipolar type. This type of motor has six leads that connect to two sets of coils, with two coils in each set. Surplus motors often don’t include complete documentation, but you can sort out the leads with an ohmmeter and some experimenting. Begin by looking for a lead that measures an equal resistance (typically 5 to 50 ohms) to two of the other leads. Wire this lead to +5V and pin 2 of U5. Wire the two leads that connect to this lead to pins 1 and 3 of U5 through diodes D1 and D2. Swaping the leads at pins 1 and 3 will reverse the direction of the motor. Identify and wire the remaining three leads in the same way, but using pins 6, 7, and 8 of U5. The 5V motor is powered directly by a +5V supply. This simple drive circuit is fine for many applications, especially at lower speeds. You can find examples of other drive circuits in the documentation from Airpax or other motor manufacturers. The data sheet for the ’5804B recommends adding D1-D4 to prevent problems in the logic circuits due to mutual coupling in the motor windings. Schottky diodes have a smaller forward voltage drop (0.25V) than other silicon diodes. Resistors R1-R4 and capacitor C1 set the frequency of U4’s output. To select a speed, you write a number from 1 to 15 to bits 0-3 of the output port. Each bit controls one of U3’s switches. For example, when pin 2 of U2 is high, pins 1 and 2 of U3 connect, and R1 is one of U4’s timing components. When pin 2 of U2 is low, pins 1 and 2 of U3 are open, and R1 has no effect on U4. When more than one switch is closed, the parallel combination of resistors forms the timing resistance. When all switches are open, U4’s output is high and the motor stops. In addition to the frequency of the step input, motor speed depends on the step angle of your motor and the mode selected at U5. A typical motor has a step angle of 18 degrees, which means that it requires 20 steps (360/18) for one full rotation. Using the resistor values shown and a motor with an 18-degree step angle, the motor speed will vary from 1 to 15 Hz in wave-drive or 1-phase mode. For a different range of speeds, use the formula shown to select resistor and capacitor values. For speeds from 10 to 150 Hz, use 0.01 microfarad for C1, or decrease the values of R1-R4 by a factor of ten. The formula assumes that in the series R1-R4, each resistor is half the value of the preceding one. If you use a different resistor scaling, you’ll have to calculate the values of the parallel combinations of resistors to find the resulting frequencies. Bits 5 and 6 of the port select the operating mode. Wave-drive mode powers one phase at a time, while two-phase drive powers two phases at once, and half-step drive alternates The Microcontroller Idea Book 193
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
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: Control Circuits Listing 11-2. Demo
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 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
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In Figure 3-1, tie pin 31 of U2 (EA
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Related Products 15 Related Product
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Finally, a compiled BASIC program u
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Related Products Figure 15-3. Blue
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Sources Appendix A Sources This App
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Programming and Interfacing the 805
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Sources Product Vendors The followi
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Sources Electronics 123 17921 Rowla
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Sources Micro Future 40944 Cascado
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Sources Siemens Components 2191 Lau
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Programs for Loading Files Appendix
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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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