SERIN from Multiple Pins

John R.

I'm new to STAMPs, and have a BS2 reading from an RFID reader, processing the tag, and spitting output to an LCD.

So far, so good.

I'd like to add a second RFID reader, on another pin.

I've got the SERIN waiting for the $0A character.· Is there a way to have a second SERIN command "active", or way to switch "back and forth" between two (or more) pins until one has a signal?

Is this something one of the other chips (with a build in buffer) could handle better?

The ultimate application would be a number of RFID readers on a model railroad reporting back any tags (in order) that passed over them.


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John R.

8 + 8 = 10

Chris Savage

John,

·· You could employ short time-outs on your SERIN statement.· That would let you switch between the two when one isn't getting any data.· The Help Files and BASIC Stamp Manual explain the timeout feature quite well.


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Chris Savage
Parallax Tech Support
csavage@parallax.com

Tom Walker

Since the Stamp is single-tasking, watching multiple ports with SERIN is not possible. Your best bet, using the Stamp, would probably be looping through multiple SERINs with short timeouts.

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Truly Understand the Fundamentals and the Path will be so much easier...

John R.

Thanks for the replies. I saw some of that in the help, and being new, didn't quite grasp the practical impications. I'll give it a shot tonight or over the weekend and see what happens.

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John R.

8 + 8 = 10

Jon Williams

As has been suggested, you can use the BS2's timeout feature of SERIN to switch back and forth -- here's a simple framework:

Main:
· GOSUB Get_Tag
· ' rest of program that handles tag
· GOTO Main

Get_Tag:
· SERIN RFID1, T2400, 1000, Get_Tag2, [noparse][[/noparse]WAIT($0A), STR buf\10]
· RETURN

Get_Tag2:
· SERIN RFID2, T2400, 1000, Get_Tag, [noparse][[/noparse]WAIT($0A), STR buf\10]
· RETURN

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Jon Williams
Applications Engineer, Parallax

John R.

Jon;

Thanks for the snipets, the light bulb is now glowing brightly!

I was thinking of the "timeout" function more as an "error condition", not a way to do the multi-tasking. It's probably even in the docs, but being the impatient American, after instant results, I was skimming...

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John R.

8 + 8 = 10