UART vs software RS232

[mackrackit]

That is how you WAIT using SERIN
From the manual:

‘ Wait until the character “A” is received
serially on Pin1 and put next character into B0
SERIN 1,N2400,[“A”],B0

You are waiting on
[QUAL1, QUAL2]

Now to use a time out, again from the manual

SERIN
Pin,Mode,{Timeout,Label,}{[Qual...],}{Item...}

See what we can do here

SERIN PORTA.4, T1200, [QUAL1, QUAL2], LOWER, HIGHER

change to this to wait on two QUALs and if QUALs are not received in 100ms, then it jumps to "LABELofCHOICE"

SERIN PORTA.4, T1200,100,LABELofCHOICE, [QUAL1, QUAL2], LOWER, HIGHER

Me thinks you are looking at this to hard, relax a bit .

[Michael]

You're right -- that's always the case.

In fact, here is the conclusion.....

I "thought" that I had my code at T1200 but it was at N1200.....BUT, I didn't really care anyway because it was my (mis) understanding that as long as BOTH pics were the same, that it didn't mean diddly squat.

After all, it's just inversion isn't it?...and I was using CMOS inverters on my breadboard...so in my mind, I was trying it "both ways". ?

So, anyway, I just changed both sides to T1200 (I know, that was suggested in the first place).....and all is fine.

BUT what am I missing here?

Like I say, when I set up my wired connection, it didn't matter if I used T1200 or N1200....as long as the were both the same.....it worked either way......so, what am I missing here?

What a pisser.

--Michael

[Michael]

Also --

Is there ANYTHING I can do other than changing the code to T1200?

I have some units already out there using N1200 and was hoping to add wireless function to them.

Again, I tried 4011's but no luck.

When I say anything, I mean ANYTHING.

Could I put another PIC in my wireless module and do something there?

[Michael]

I think also Brian may have hit on it but I still can't plant in my mind why N or T even matter.

He commented that without a line driver use N....with, use true.

I suppose there may be a driver on the module but I'm still totally in the dark why N and T even make a difference -- I mean data is data -- whether it's upside down or not?

[Bruce]

With your wired connection you had full control over both modes so you could just program
both PICs to send/receive in inverted or non-inverted modes.

With the Maxstream units your only option is to program the sending/receiving PICs to use
non-inverted modes - if connected directly to the Maxstream modules.

If you prefer inverted mode, then a simple inverter on both ends should do the trick, but it
has to be fast enough to handle whatever data rate you use without messing with timing.

I would opt for a simple firmware change before adding new hardware though. Just my 2c.

data is data

Data is data, but inverted or non-inverted does matter. Think about about it like this -
suppose you program a PIC to receive data in non-inverted mode. This PIC is the RF
module. Now connect another PIC to it that you've programmed to send & receive in
inverted mode. It doesn't work.

If you reprogram the 1st one to use the same mode, it works. You have control over that.
You don't with the Maxstream unit. So you program controllers on both ends to use the correct
mode, or insert a data inverter.

[Michael]

Ok Bruce....thanks.

It's working fine with a direct connection using T1200 on both.

I HAVE to get this solved in hardware though because I have some product out there and the pics are N1200.

Dagnabit...I tried a 4011, a 4093 and even a transistor and couldn't get it to work. I used pullups....tried it all.

Certainly a 4011 can handle the 1200 baud? I'd appreciate any ideas but I must get this thing to work with some external hardware.

I'm using a 4mhz osc but that's not an issue....I just need to pass the 1200 baud right?

I'll always use non-inverted from now on!

[mackrackit]

Maybe the 4011 is wired backwards for the direction you need to go? Never used one, just guessing.

[Michael]

Sorry to bore you guys with all of this but that's the wonderful thing about forums --
MORAL support.

I now have that eureka moment.

As it turns out, my ultimate intention was to use an RS485 line driver with my wireless because that's the way my wired connection is set up.

But all of my experiments were with the driver out and RS232...I figured I'd work my way up.

Bottom line....

If you want to use N1200 in your PICS, use an SN75176 and simply reverse A and B on the 485 side.

Works great now.

For the life of me though, I couldn't get the RS232 hardware inversion to work.

HIP HIP FRIGGIN HOORAY.