Build the Machine Science XBoard, with a programmable microcontroller.

Transcription

1 Build the Machine Science XBoard, with a programmable microcontroller. Site: icode Course: Machine Science Guides Book: Assembling the XBoard Printed by: Guest User Date: Monday, May 24, 2010, 10:46 AM 1 of 19 5/24/ :47 PM

2 2 of 19 5/24/ :47 PM Assembling the XBoard The Challenge: Build the XBoard Collecting Your Components About the Microcontroller Installing the Microcontroller About the Oscillator Installing the Oscillator About the Capacitor Installing the Capacitor Identifying Your Programming Hardware Setting Up the USB Programming Linkage About the LCD Installing the LCD More Practice with Schematics Final Hardware Check

3 3 of 19 5/24/ :47 PM The Machine Science XBoard is a configuration of wires and components on the breadboard that will allow you to rapidly build sophisticated electronics and robotics projects. The XBoard's key component is a PIC microcontroller: a tiny computer on a chip. The microcontroller can be programmed with a set of instructions, called code, which determine how it behaves. The XBoard will be the control center for many Machine Science projects, from digital stopwatches to remotecontrolled robots! Figure 1 shows the completed XBoard. Figure 1. The Machine Science XBoard.

4 4 of 19 5/24/ :47 PM In this challenge, you will build the XBoard by adding a microcontroller to the breadboard. You will also connect a variety of different components to the breadboard, including an oscillator, a capacitor, a reset button, and a programming linkage. In the next unit, you will practice programming the microcontroller, using an existing code file.

5 5 of 19 5/24/ :47 PM The components needed to build the XBoard are listed in the table below and shown in Figure 2. Part Quantity Description A 1 Microcontroller (PIC16F877) B 1 Liquid crystal display C 1 Resistor (4.7K-Ohm) D 1 Oscillator (4.0-megahertz) E 1 Capacitor (0.1-microfarad) F 1 USB programming board G 17 Jump wires (6 yellow, 6 orange, 2 long red, 1 short red, 1 brown, 1 white) Figure 2. XBoard components.

6 6 of 19 5/24/ :47 PM The microcontroller is the XBoard's "brain," a tiny computer on a chip, which can be programmed to perform specific tasks. The XBoard's microcontroller, shown in Figure 3, is just like those found in many commercial devices. It has 40 pins, which plug directly into the XBoard. Figure 3. The XBoard's microcontroller. In recent years, microcontrollers have become smaller, more powerful, and less expensive. As a result, they have been incorporated into more and more everyday products, from cell phones and pagers to home appliances and automobiles. Figure 4 shows some of the systems in modern automobiles that rely on microcontrollers. Figure 4. Automobile systems that rely on microcontrollers.

7 7 of 19 5/24/ :47 PM 1. Orient your breadboard so that hole A1 is in the lower-left corner. 2. Orient the microcontroller so that the pins are pointing down, and the small circular indentation is in the lower-left corner of the top face. 3. Find pin 1, which is directly beneath the circular indentation on the microcontroller. 4. Insert the microcontroller into the breadboard, aligning pin 1 with hole C7, as shown in Figure 5. Be sure all 40 pins are properly aligned before applying pressure to insert the microcontroller. NOTE: You may have to bend the pins slightly to align them. Once all the pins are aligned, be sure to push microcontroller firmly down until it CLICKS INTO PLACE. Figure 5. Top view of the breadboard with the microcontroller installed.

8 8 of 19 5/24/ :47 PM To perform its tasks, the microcontroller needs to keep track of time. It does this with an oscillator, a component with a crystal that vibrates at a constant 4 million times per second. The oscillator is like the XBoard's "clock." By dividing each second into many small units, oscillators help coordinate the actions of the microcontroller. The oscillator has three pins. The middle pin connects to ground. The outer pins connect to the microcontroller via jump wires. Figure 6 shows the oscillator. Figure 6. The XBoard's oscillator (left) and a clock (right).

9 9 of 19 5/24/ :47 PM 1. Carefully insert brown, white, and yellow jump wires into the board, as shown in Figure 7. The brown wire connects hole B20 to hole B30. The white wire connects hole A19 to A28. The yellow wire connects hole A29 to ground. 2. Insert the oscillator, with the printed text on the component facing you (Figure 7). The oscillator's three prongs should go in holes D28, D29, and D30. NOTE: You may have to trim excess wire from the oscillator's prongs in order to seat it as shown. Figure 7. XBoard with the oscillator installed.

10 10 of 19 5/24/ :47 PM Like many electronic devices, the microcontroller is sensitive to surges in power, which can cause it to malfunction. Occasionally, the battery pack's power surges. To even out these surges, the XBoard has a component called a capacitor, which stores the extra electricity during a surge and then releases it slowly. The capacitor protects the microcontroller, just as a surge protector protects your computer from power surges in your home. Figure 8 shows the capacitor. Figure 8. The XBoard's capacitor (left) and a home surge protector (right).

11 11 of 19 5/24/ :47 PM 1. Insert one end of the yellow wire into hole A18 and the other end into ground. Similarly, insert one end of the orange wire in hole A17 and the other end into power, as shown in the video and Figure Install the capacitor on the board, inserting the capacitor's two prongs into holes B17 and B18. NOTE: You may have to trim excess wire from the capacitor's prongs in order to seat it as shown in Figure 9. If the capacitor has text on it, be sure that the text is facing towards the microcontroller. If it has no text, or text on both sides, you may insert it in either orientation. Figure 9. XBoard with the capacitor installed. 3. Next, make two more connections to power and ground on the top side of the chip, connecting hole J15 to power and hole J16 to ground, as shown in Figure 10.

12 12 of 19 5/24/ :47 PM Figure 10. Power and ground connections on the top of the microcontroller.

13 13 of 19 5/24/ :47 PM To program the microcontroller, you must establish a linkage between your computer and the PIC microcontroller. Kits shipped after June 2009 include a USB programming board with two rows of male headers that plug into the breadboard to the left of the chip. Instructions for installing these newer units are included in this tutorial. Instructions for older programmers are included in the Older Kit Components section. Figure 11 shows the programming components included in Breadboard Starter Kits of different ages, starting with the oldest. Figure 11. Serial (top) and USB (bottom) programming linkages.

14 14 of 19 5/24/ :47 PM The newest version of the USB programming linkage comprises a mini USB cable and a programming board with two rows of five pins. This design provides more stability on the breadboard. The new device also has an integrated reset button, eliminating the need for a separate button switch on the breadboard. 1. Using two long red jump wires, connect hole I1 to hole I21, and hole H2 to hole H22, as shown in Figure 12. Then, use a short red jump wire to connect hole B5 to B7, use a yellow jump wire to connect hole A3 to ground, and use a 4.7K-Ohm resistor to connect hole A5 to power, as shown. NOTE: The 4.7K-Ohm resistor has a yellow band, a purple band, a red band, and a gold band. You may have to trim excess wire from the resistor in order to seat it as shown. Figure 12. Jump wires for XBoard's programming linkage. 2. Orient the USB programming board so that the mini-usb jack is on the left side. Insert the two five prong-headers into the breadboard on either side of the center groove, in holes E1 to E5 and F1 to F5, as shown in Figure 13. Figure 13. Inserting the USB programming board.

15 15 of 19 5/24/ :47 PM 3. Connect the mini-usb cable to the USB programming board, as shown in Figure 14. Figure 14. Connecting the USB cable. 4. Connect the free end of the USB cable to any free USB port on your computer, as shown in Figure 15. Figure 15. Connecting the USB cable to your computer.

16 16 of 19 5/24/ :47 PM A liquid crystal display (LCD) contains a thin layer of liquid crystal that changes from light to dark when electricity is supplied to it. The XBoard's LCD can display text and graphics, like a miniature computer screen. LCDs are everywhere--in digital watches, household appliances, and handheld video games. Figure 16 shows the XBoard's LCD. Figure 16. Liquid crystal display (LCD).

17 17 of 19 5/24/ :47 PM 1. Using a yellow jump wires, connect hole J29 to power. Use two orange wires to connect holes J28 and J30 to ground. Use a fourth orange wire to connect hole J24 to hole J27, as shown in Figure 17. Figure 17. XBoard with jump wires for LCD installed. 2. Insert the LCD's pins into holes I17 to I20 and holes I25 to I30, as shown in Figure 18. Figure 18. Aligning LCD's pins on XBoard.

18 18 of 19 5/24/ :47 PM Figure 19 shows a schematic diagram of the XBoard. Can you identify each element in the schematic? Figure 19. Schematic of XBoard.

19 19 of 19 5/24/ :47 PM Before moving on to the next challenge, take a few minutes to check your hardware set-up. The following checklist will help you ensure that your XBoard is ready for programming. Microcontroller: Pin 1 should be in hole C7. The microcontroller should be pushed firmly down into the breadboard. Oscillator: The oscillator's pins should be in holes D28, D29, and D30. The text on the oscillator should face you. Capacitor: The capacitor's pins should be in holes B17 and B18. If the capacitor has text on it, the text should face away from you (toward the chip). If the capacitor has text on both sides, it can be oriented either way. Reset button: If your board has a manual reset button, the button's pins should be in holes C3 and C5. The short red jump wire should connect holds B5 to B7. Programming linkage: The long red jump wires should connect hole I1 to hole I21, and hole H2 to hole H22. LCD: The right-most pin of the LCD should be in hole I30. Battery leads: As always, the red lead from the battery pack should align with a red line hole, and the black lead should align with a blue line hole. Power and ground: A single red jump wire should connect the power (red line) holes on the top of the board to the power (red line) holes on the bottom of the board. Also, a single red jump wire should connect the ground (blue line) holes on the top of the board to the ground (blue line) holes on the bottom of the board.