consumption figure allows the Wasp electronics to run
powered only by a single 3. 3 volt coin cell.
The Wasp design is similar in thought to that of the
military Humvee. There are many roles this robotics
processor can take on depending upon how it is equipped
and configured. For instance, the Wasp is perfect for data
logging missions as it can be programmed to store
analog-to-digital readings into its internal EEPROM or
external serial Flash. It can be loaded with serial Flash
parts that range from 512K to 8M of eight-bit
storage. The ATmega644’s ability to support an
external 32.768 kHz clock crystal further adds to the
Wasp’s data logging prowess as data logging can be
tied to time of day or timed events via the
ATmega644’s real time clock. In addition, the Wasp
can sleep until the real time clock awakens the
ATmega644 to take a reading.
SPI and I2C portals are common to most
microcontrollers and the ATmega644 is no exception.
The Wasp uses the services of the ATmega644’s SPI
portal to communicate with the serial Flash. Atmel’s
acronym for I2C is TWI (Two Wire Interface). The
Wasp utilizes TWI architecture to communicate with
other I2C-based smart peripherals. The Wasp’s I2C
portal consists of a male Molex connector that also is
pinned to power or be powered by external I2C
devices. The Wasp can run at 3. 3 volts or 5.0 volts.
When external serial Flash is installed, it is
recommended to power the Wasp at 3. 3 volts to
avoid releasing the serial Flash IC’s magic smoke. The
only way to fly the Wasp with a 20 MHz crystal is to
power the silicon polistes exclamans with 5.0 volts.
Another peek at Photo 1 reveals the presence of
8 Mbytes of serial Flash. I flipped the Wasp over in
Photo 2 to show you the Freescale Semiconductor
MMA7260 three-axis accelerometer IC. The smaller IC
just above the MMA7260 is a Burr-Brown DAC8501
digital-to-analog converter IC. Both the MMA7260
and DAC8501 are optional components. In that the
serial Flash and accelerometer are installed, the
crystal you see in Photo 1 must be a 10 MHz part.
Photos 1 and 2 tell us what stuff the Wasp is
made of. However, Figure 1 provides a detailed view
of the Wasp’s I/O subsystem and power
assignments. When the Wasp isn’t sitting on its nest,
the SPI portal on digital port J2 can be used to
program the Wasp’s AVR. Note that the AVR’s UART
interface (RXD and TXD) is located on digital port J3
along with the pinned out I2C portal (SCL and SDA).
In the old days of
the EDTP ATA hard drive
controller, the AVR
wanted to see a 10-pin
ICSP termination. These days, the latest AVRISP mkII is
fitted with a six-pin ICSP termination. The Wasp I received
PHOTO 1. This is a Wasp. Instead of a stinger, wings, big eyes,
and six legs, you’re looking down on an Atmel ATmega644
microcontroller, 8 MB of Atmel serial Flash, a 10 MHz CPU crystal,
a 32.768 kHz real time clock crystal, and various capacitors
and resistors. The Molex connector is a powered I2C portal.
PHOTO 2. This is an underside shot of the Wasp. The Burr-Brown
DAC8501 shares the spotlight in this photo with the optional Freescale
MMA7260 three-axis accelerometer.
SERVO 09.2010 53