Serial Howto?

Oldbitcollector (Jeff)

My current project required a 8x8 keyboard matrix, so I decided to put that load on something cheap, a $4. picaxe 28x (since I didn't want to give up all those pins on the prop) It's handling those inputs, and sending data out it's serial connection at 4800 baud. The picaxe output is standard RS232 at 5v.

I'm assuming that if I tie it's output to the prop through a 10K resistor, I should have reduced the voltage to a safe level, and use "FullDuplixSerial" to read the datastream?
Or is there another way I should be looking at to handle this? I keep bumping into this 3v/5v difference when dealing with other chips. Common?

Oldbitcollector

Mike Green

There is a whole long thread about connecting the Propeller to voltages higher than 3.3V. It's one of the "sticky threads" at the beginning of the forum (HOW TO SAFELY INTERFACE A 5V SIGNAL TO THE PROPELLER?). It's chock full of information. For your particular case, a 10K series resistor should work fine.

Oldbitcollector (Jeff)

I suspected that thread applied.. Thanks for confirming this..

Oldbitcollector

QuattroRS4

Oldbitcollector,
You could use a serial line driver I.C like the max232 - used for the propstick see attached link

www.parallax.com/dl/docs/prod/prop/PropStick-v1.2.pdf


if you are not going to use this interface to program the prop also you can omit the reset circuitry.



also have a look at this thread



http://forums.parallax.com/showthread.php?p=632975

this is a sample serial interface using a (2.5v to 5.5v)·max232 derivative
http://forums.parallax.com/attachment.php?attachmentid=45449

in the above schematic - if you do not wish to use this interface·to program a prop
then leave out everything connected to pin12 of the st232 (U4 in diagram) i.e.
no connection to pin12 of U4 - C5,R5,R6,Q1 are not required and therefore neither
is a connection to RSTn (pin11 of U1 - The Prop) and you do not need the connection
from pin4 of the DB9F to pin13 of·U4 (the above named·components/connections are required if this interface is used to program a prop)·- you are not tied to using the 2 prop
pins shown for tx/rx either·if you are not programming·with this interface·just ensure the pins are assigned in the serial object you will use..



this a 2.5v - 5.5v max 232 derivative
http://forums.parallax.com/attachment.php?attachmentid=45447

Regards,

Quattro

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'Necessity is the mother of invention'

Post Edited (QuattroRS4) : 4/4/2007 11:23:07 AM GMT