Chipcon AS
SmartRF
®
CC2420DBK Demonstration Board Kit User Manual
(rev. 1.3) 2004-11-03 Page 8/ 52
RS-232 interface
A serial port is included on the CC2420DB. This port is used when software is programmed
into the AVR MCU using the bootloader, and is also used by several of the example
programs. The port includes support for RTS/CTS-type hardware flow control (handshaking).
Microcontroller and user interface
The microcontroller used is an AVR Atmega128L from Atmel. This controller has 128 KB of
Flash program memory, 4 KB of SRAM data memory and 4 KB of non-volatile EEPROM data
memory. The controller is interfaced to the CC2420 via its built-in SPI interface as well as
some general I/O pins.
The MCU is also connected to four LED’s, a joystick and an extra button for user interface
purposes. The different examples use these peripherals differently. An analog temperature
sensor, a potentiometer and 64K of external RAM are also included.
An ISP and a JTAG ICE connector are provided for programming the AVR without using the
serial port. In this case an Atmel AVR JTAG or ISP programmer should be connected to their
respective connectors.
All of the I/O pins are connected to footprints for 2 x 10 pin-row connectors. These connectors
are compatible with Agilent logic analyzer probes, and can be used either for testing or for
prototyping. For instance, it is possible to add a daughter board with additional circuitry using
these connectors.
External RAM
The lower 4 Kbytes of the external RAM is overlaid by the Atmega128L internal register and
RAM. CC2420DB includes this memory because it can be used for debugging purposes, to
buffer and store data if desired. The 32 kB RAM size is not a requirement nor necessary for a
low cost a Full Functional Device (FFD) or Reduced Functional Device (RFD). Please refer to
the Atmega128L data sheet for more details.
Flash Memory Requirements
The flash requirement for a FFD device with the Chipcon MAC will be approximate 20 kBytes
and 10 - 16 kBytes for a RFD. Additional flash size must be available for the application.
Important:
The memory requirement will be dependant on compiler, optimization level, hardware
platform and feature used in the stack.
CC2420DB Low Power Mode support
To apply a low power mode with CC2420DB for application development, it will be necessary
to apply an additional clock source together with the 8 MHz crystal. The Atmega128L
provides the Timer/Counter oscillator pins (TOSC1 and TOSC2), and these pins are available
on the CC2420DB connector P3. The oscillator is optimized for use with a 32.768 kHz crystal.
This clock source can be connected the following ways.
1. A crystal can be connected directly between the pins.
2. An external clock source can be applied to the TOSC1. Atmel does not recommend
this method.
The 32.768 kHz crystal will clock the timer 0 and then the overflow or compare match timer
interrupt is applied to wake up Atmega128 from power save mode.
