May
2006, Issue 190
ARM-Based
Modern Answering Machine
Philips
ARM Design Contest 2005 First Prize
SYSTEM
OVERVIEW
The
TAM-TAM is built around an LPC2138 microcontroller (see
Figure 2). The microprocessor shares its SPI bus with
an SD/MMC card reader and a Microchip Technology ENC28J60
Ethernet controller. (I used a Kingston Technology Elite
Pro SD/MMC flash card, but you can insert any card in
the reader.) Two chip select lines direct the SPI bus
transfers to the flash memory card or to the Ethernet
interface (see Photo 2).
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(Click
here to enlarge)
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Figure
2—Study the connections among the different subsystems.
The LPC2138 microcontroller and its SPI bus form
the TAM-TAM’s core. |
|
(Click
here to enlarge)
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Photo
2—The PCB I designed integrates all of the components.
Different subsystems are designed around the LPC2138
microcontroller. J1 mates with a debug board that
includes a level translator and two DE9 connectors. |
Individual
GPIOs control the LEDs and the front panel switches.
The integrated ADC that’s directly connected to the
line interface is used for recording from the telephone
line. The DAC is used for local playback on the speaker
or remote playback on the telephone line. You may download
a complete schematic from the Circuit Cellar FTP site.
I
initially developed some of the subsystems with a Keil
MCB2130 development board. I developed a PCB when I
was confident that the project would be successful.
