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Serial Question

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m1tch37

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Gday

I am familiar with using serial devices with a PIC using RX and TX.

A device i am planning on purchasing (http://www.wiznet.co.kr/pro_eg_EGSR7150MJ.htm) has serial signals TXD, RXD, RTS, CTS.

I assume TXD and RXD are TX and RX, but what is RTS and CTS and how do i use them?

Secondly, on the subject, do you think the EG-SR-7150MJ is a good Ethernet to Serial gateway? I was originally looking at the XPORT, its better, but more expensive.

Regards,
Mitch
 
RTS - request to send
CTS - Clear to send.

those are flow control signals. how you use them depends on whether you are implementing a terminal (DTE) or a computer (DCE). For a DTE, you want to send something, you raise RTS and wait for CTS to be raised.

note that the ethernet device also supports xon/xoff flow control. might be easier.

what does the EGSR7150MJ cost? I could only find an eval kit price ($190). I've used the xport - it's $50. don't really need an eval kit for it - I made my own board.

edit: I found it. wow. $34 USD, not bad. That's worth buying to check out. supposedly supports 100 mhz though that's unlikely to matter much as the max serial speed is 230K.
 
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Thanks for your help philba.

First of all still on RTS/CTS, so i first must wait for my request to be cleared when sending a message, but do i have to clear incoming requests, or does it assume im ready?

Secondly, xon/xoff. After reading this i understand it will just send me a stop message, where if the stop pin is high/low (?) i just wait till its not, but what pin does it use, and do i stop when its high or low.

Or should i just use no flow control, im not sending much information?

On to the boards, i like the xport for its size only, but i suppose its not worth the $15. The EG-SR-7150MJ looks fine otherwise.

Regards,
Mitch
 
yes. basically.

xon/xoff is an in-line control. you send a ctrl-S (character value 19) to stop the flow. send a ctrl-Q (17) to resume the flow.

If you are sending small packets, try it without flow control. If your messages are smaller than the internal buffer, it should be just fine.
 
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