Sunday, June 24, 2012

Step 1: Testing Components

Now it's time to put the parts together. Since the Bluetooth module does not already have the pins installed, attaching those is the first step. I used a small piece of Category 5e Ethernet cable, since the Bluetooth module needs six pins, and a Cat 5 cable has six wires inside. So I soldered one end of the Cat 5 cable onto the BlueSmirf Bluetooth module. I would recommend using a pair of wearable magnifying glasses, and getting someone to hold the module. Soldering the wires takes a significant amount of precision, so make sure you don't melt any part of the board or make the solder bubbles contact each other.
Since we don't need two of the wires, I cut off the Brown and Brown/White colored cables, and used the following wiring setup:
Wire                      Pin
Green/White      CTS-I (for use of hardware flow control)
Orange               VCC (power)
Orange/White    GND (ground)
Blue                   TX-0
Blue/White        RX-I
Green                RTS-0 (for use of hardware flow control)

I used this site to help with setting  up the wiring. Since the Bluetooth module in my laptop is currently acting up, I paired it with my Droid Incredible smartphone. Once it was all hooked up, it paired with little problem. One difference between 'Step 4' in the link and what I had to do was that the module paired as RN42-C280 rather than BlueRadios, and the passkey was '1234' rather than 'default'. Final soldered module pictured below:

With no application installed on my phone, I tested the performance of the board while plugged into my laptop. First I installed a LED and a resistor on the board as described here, in the 'Blink' tutorial.
Since I didn't have a 220-ohm resistor, I installed a 470-ohm resistor and 560-ohm resistor in parallel, which yields an effective resistance of 256 ohms, good enough for the test. Following the other directions in the blink tutorial, the diode blinked with no trouble. Moving on to test the servo, using the 'Sweep' tutorial, I used another cat 5e category to lengthen the servo cable to reach each necessary pin.

The sweep program uploaded fine, but it did not work exactly as planned. The analog nature of the servo did not allow for the precise positioning, something I was afraid of. So it looks like I will have to invest in some digital servos. But a good start, and good to know everything works.

Status update:
Time spent (3 days): 11 hours
Cost expended (prices given include paid shipping): $122.79 (if you don't have resistors and Cat 5e cables lying around, you may have to buy some for a few dollars)

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