Nuts and Volts - August 2008

■ FIGURE 6. RS-232 DB9 connection.

provides a suitable substitute component that the user must solder to the Butterfly to use the light sensor function. This sensor works with the existing Butterfly software.

The CdS light sensor is a device that has resistance proportional to the incident light. As a resistor, the device has no polarity so either leg can be inserted in the pads shown circled in red (see Figure 5). Seat the sensor snug to the top of the Butterfly, then solder the legs to the bottom and trim them just above the solder meniscus.

provided DB- 9 female connector (calm down — it’s technical).

Strip about 1/8 inch from the ends of each wire and then carefully solder them to the Butterfly and the DB- 9 connector as shown in Figure 6. Notice that the upper wires in the picture cross. Be very careful to get this exactly according to Figure 6; about half the emails I get for problems turn out to be related to either incorrect wiring or poor soldering of this component.

Female Headers

foamcore box. (Details for this construction can be found in Smiley’s Workshop 1 Supplement: AVR Learning Platform Foamcore Base and Box at www.nutsvolts.com.)

You will need to carefully twist the ends of the battery box wires until they are straight, then soak them with solder so that it runs up under the insulation to make these wires strong enough to insert into the breadboard power bus. The red wire goes to the + red bus and the black wire goes to the – blue bus. Connect the two power busses with red and green wire and then put an LED with a 2.2K resistor on the breadboard. The resistor goes to the + power; the LED short leg goes to the – power. The LED and resistor are then connected on a breadboard strip.

The Butterfly receives power from the bus as shown, the + red wire goes to the rightmost top of the header, and the – green wire goes to the rightmost bottom of the header.

DB9 Female Connector and Wire

In order to communicate with a PC, the Butterfly must connect to a serial cable. The mini-kit provides the connector and wire to make the connection to a serial cable.

The Butterfly has built-in RS-232 converters for serial communication with a PC. Most serial cables will have a DB- 9 male connector on the device side that will mate with the

Refer to Figure 7 to see the location of the ADC, USI, PORTB, and PORTD pads. Solder the two-pin header to the ADC pads; the four-pin header to the USI pads; and 2x5 headers to the PORTB and PORTD pads. Notice that Figure 7 shows a male header on the ISP pad; this is not included in the kit and won’t be used for our work (maybe later).

Test Your Connection Using Developer Terminal

AVR Learning Base Board

■FIGURE 7. AVR Workshop Learning Platform.

The AVR Workshop Learning

Platform is built on a foamcore board that lives in a protective

Hook your Butterfly DB- 9 connection to an RS-232 cable from a PC. If you use a USB-to-serial converter cable, you may have problems if the voltage levels are not robust. I’ve used several and have not had a problem.

Open Developer Terminal.

You can read the user manual

(I recommend: RTFM) by clicking the ‘Help/Manual.’ Click the ‘Settings/Port’ menu item to open the settings window. Select the RS-232 COM port that the Butterfly is connected to. Set the baud rate to 19200, data bits to 8, parity to None, stop bits to 1, and handshaking to none. You can test that your learning platform is