RS232 adaptor for debugging...

Jim G.

I am getting ready to create a little project and want to make sure I can't
just buy the thing before I make it.

In most of my SX projects I try to reserve port·A for diagnostic serial I/O, but I don't
want to put a MAX232 chip permenantly on the board.· So my idea is to
put a 6 pin header·on·the main·board with +5, Gnd, and RA.0 - RA.3,
sort of like how the SX-Key connects.

Then I want to plug·an interface board, a lot like the SX-Key, on to that
6 pin header, and connect it to my PC terminal program.· The only thing on
this little board is a DB-9S, MAX232, and a 6 pin female header.· Like I said,
this is really like the SX-Key, but with an RS-232 chip, and nothing else.

Depending on the application, one could output run-time status messages
out this port, but normally nothing is connected.· Plug on this little board
and easily watch the messages fly by...

Any comments about this will be appreciated,
Jim G.

David B

I did something like this with a Seetron LCD display. The Seetron will accept TTL levels, so you can send text messages directly from the Scenix to the Seetron LCD with no need for an RS232 converter. I've got a little stub of RS232 transmit code that can copy into pretty much any project to give it RS232 message output capability.

PCs also will usually accept TTL into the serial input.

James Newton

http://www.sxlist.com/techref/io/serial/RCL1.htm·$17 Now in stock. Proceeds help to support sxlist.com.

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Jim G.

Thanks for the note James, I just placed an order...

I also like David's idea about using an LCD module, and will look in to that as well.

Thanks all,

Jim G.

allanlane5

Nice form factor, James. Put the MAX232 adapter inside the hood, thus taking effectively no target board real-estate. Clever.

Paul Baker

Alot of serial programming cables do that, the Atmel JTAG cable I made converts the levels and buffers the signals inside the hood (I don't take any credit for it, I just followed online assembly directions).

James Newton

The other thing is that true RS232 level conversion is VERY seldom actually needed. In most cases, a simple resistor will do. See:
http://www.sxlist.com/techref/io/serial/ttl-rs232.htm for some very useful "cheats" which will work most of the time.

I leave the MAX232 chips off and just keep the RLC1's around for the few cases where they are really needed.

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---
James Newton, Host of SXList.com
james@sxlist.com 1-619-652-0593 fax:1-208-279-8767
SX FAQ / Code / Tutorials / Documentation:
http://www.sxlist.com Pick faster!