Bluetooth Radio Link

This page shows the serial communication cable replaced by a Bluetooth radio module. This radio was purchased from A7 Engineering ( for $70. This is a 2.4 GHz bidirectional radio link that is about the size of a credit card. It can talk to the Mac via a tty driver, so is compatible with the software I have already developed to talk to the chip, and to the ATMega32 chip via the onboard USART TX and RX lines without any additional components.

Actually, the first unit I received had a problem with the input line, in that it could receive OK, but would not transmit anything back to the Mac. But I was able to thoroughly document the problem, and when I contacted A7 support they were kind enough to send me a new unit free of charge, which works just fine. In the meantime I've been playing with developing my own digital radio from scratch (although complete radio chips like the CC1100 and CC2500 are only $4), and may eventually return to that project as I need more link nodes. I generally feel that I should understand and be in control of all aspects of the system, and so would like to develop my own radio setup.

Here is a photo of the radio operating stand-alone, powered by a 7805 voltage regulator and a 9V battery. The LED at right indicates that it has a connection to the Mac, and the LED at left flickers as data is received by the unit:

Here is a photo of the unit connected to the ATMega32:

The Mac is sending bytes to the tty driver, and the chip is running a simple program that displays each byte on the LEDs, and then increments the value and returns it to the Mac. The radio is being powered by the AVR development board, and both are sitting in a different room than the Mac, about 10 meters away with several walls in between. The link has been running for about an hour now, with no problems or interruption. Note the lack of a connection cable.

The next step is to create another circuit board for the AVR chip and radio that will recieve instructions from the Mac, send commands to the motor controller board developed previously, and return motor/wheel feedback data to the Mac. This will complete the electronics of the first robot.

İSky Coyote 2006