Components and Tools

ComBase (MiRF2RS232)

The ComBase serves as main communication device between the PC and my robots. It's connected via RS232 to the serial com port of the PC and operates in the 2.4Ghz band. The core component is a nRF24L01 from Nordic Semiconductor. This little transceiver IC is pretty easy to use an reaches data rates up to 2Mbit/s. Driving it with the breakout module from SparkFun and a 2.4GHz duck antenna you can reach up to 80m range.

Design Comments

nRF24L01

Since the nRF24L01 supports SPI it's pretty easy to use it with an AVR controller. Also SparkFun's silkscreen labels the pin out of the breakout module self-explanatory. So connecting SCK, MOSI and MISO to the corresponding pins of the AVR is obvious. For CE and CSN I've chosen appropriate I/O pins as stated in the following table and IRQ is connected to the external interrupt 0 of the Atmel controller.

AVR ATMEGA8/168

nRF24L01

Description

PB5 (SCK)

SCK

SPI clock signal

PB4 (MISO)

MISO

SPI master in, slave out

PB3 (MOSI)

MOSI

SPI master out, slave in

PB1

CSN

SPI Chip Select

PB0

CE

Chip Enable Activates RX or TX mode

PD2 (INT0)

IRQ

Interrupt pin. Active low

RS232

To connect the AVR controller to an RS232 interface it's necessary to convert the signal levels from 5V TTL/CMOS to EIA-232 levels and vice versa. This can easily archived with an MAX232 IC.

ISP

For easier updating of the firmware the ISP pins are routed to an header compatible with the Atmel ISP10PIN.

I/O header and LEDs

PC0 and PC1 are connected to LEDs for debugging and status indication. Also PC0 to PC5 are connected to a header so this board can be used as A/D capture device. The LEDs are connected with an jumper so they can be disconnected if the PC0 and PC1 is needed otherwise.

Power Supply

The design of the 5V power supply for the AVR and 3.3V for the nRF24L01 is pretty much the same as used in the KraftModul.

Schematic Diagram

Like all my circuits I've planed the schematic diagram and board layout with Eagle.

schematic.jpg routing.jpg

Finished Board

The vigilant reader may recognize a small difference between the routing diagram and the processed board especially under the AVR. This is because of some mistakes in the first layout which I've already fixed in the diagram.

board.jpg BasisStation.jpg

Comments for further processing

Software

Documents

ComBase (last edited 2008-04-12 11:58:06 by StefanEngelke)