Re: [uCsimm] serial data->network

From: Geoffrey Wossum (gpw0341@omega.uta.edu)
Date: Tue May 02 2000 - 18:10:48 EDT


Alfred,

> I need to implement a 16kbps synchronous TTL data stream to ethernet packets
> and vice versa. My current plan is to us the UCsimm board to do this.
> By using a digital I/O line, polled at the right times, and then using
> SOCK_RAW on the ethernet interface I should be able to do this.
> So, is it possible?

As far as the 16 kbps go, we've had success hooking up a custom I2C bus
interface to the uCsimm. When data was being sent at full tilt to the
uCsimm node, the bus interface generated about 13500 interrupts a second,
not too far away from where you need to be. Having to process all those
interrupts and some background processes loaded the uCsimm up to about
0.07, so we had plenty of processing power to spare at that rate.

One important note: Our I2C bus interface had an 80 byte FIFO, so we could
afford for the kernel to wait awhile before scheduling our device driver.
I don't know if the system would have worked properly without that FIFO.

I would suggest that you have an external I/O processor with a FIFO like
we had, so you don't have to worry about not getting scheduled at just the
write time and getting corrupted data. It should be simple to get a 16C6x
or 16F87x series PIC to do the I/O processing and buffering for you, and
it would only add $6-10 to the design.

To summarize: You should be able to do it, think about using an I/O
coprocessor.

---
Geoffrey Wossum
gwossum@acm.org
Project AKO - http://rover1.uta.edu/~ako
Internet Imperialists - http://inetimperial.sourceforge.net
This message resent by the ucsimm@uclinux.com list server http://www.uClinux.com/



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