Re: Microcontroller; any suggestions?

Rich Grise <richgrise@xxxxxxxxxxx> wrote:
On Mon, 05 Jun 2006 21:00:17 +0000, pbdelete wrote:

Dala Dahlgren <dala@xxxxxxxxxxxx> wrote:
Why do you explicitly need ethernet ..?

I wanted to make a small "IP-phone" for fun. The "phone" will need a ADC/DAC
to record/replay speech, and I want to use it on an Ethernet.
So what I am looking for is a microcontroller wich can get the job done
without any external ic's.

And, yes, I know that it would be a lot easier just to use my PC for this
task, but again, this "phone" something I want to make for fun...

I guess implementing the VoIP stack completly in a MCU might be a challenge.
But if your willing to shave your spec down a bit it might just work.
Setup two software loops possible triggered by external oscillator (irq on
logic level change). Collect data under X seconds. Then have it transmitted.
And in the other loop for every packet received set every byte to the pwm
correspondingly.

If your willing to go fpga instead the challenge might be easier ;)

So, speaking of TCP/IP on an fpga, if someone did that, what would be the
recommended interface to, say, cat5?

You got to have a PHY (like Intel LXT972M) which essentially translates
between 4 bits LVTTL and baseband ethernet.
After the PHY comes 1:1 signaltransformer and various passive components.

However I suspect it's possible to interface 10 Mbps FD with an electrical hack
useing LVTTL I/O's. Not verified thoe. It would however be very touchy to any
mishaps, but cheap! ;)

And the PHY needs a 25 MHz 50 ppm crystal.

.

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