Debug/Serout/Serout2 - please, need advice ...

[fratello]

Thanks for support !
The schematic is "valid" since with the original soft works just fine ... When I "give up" to voltage monitor program (VB) I am unable to receive consistent data.

[Scampy]

Hey, wasn't being negative....like I stated - I'm no expert... if it works with the original code then the hardware is fine....

[mackrackit]

You screen shot shows 300 baud, that is why I gave the example that I did.

Now I notice you code a schematic showing 2400 baud.....

[Art]

RS232 is -12 Volts on the low, so there’s actually 24 Volt difference between one state and another.
I don’t believe it’s possible to do RS232 with any one single transistor if the ground is connected to the other device.

The whole compromise to make 5 Volt RS232 ports is just that.
It could be damaging to connect a real RS232 port to a pic without proper clamping if it didn’t have some awesome IO characteristics.

[tumbleweed]

The RS232 voltage spec:
-3V to -25V = logic 1
+3V to +25V = logic 0


However, if you take a look at a lot of the "MAX232" class chips you'll find that the RXD receiver input has the following characteristics:
Input high threshold: 1.7V (typ), 2.4V (max)
Input low threshold: 0.8V (min), 1.8V (typ)
Input resistance: 3K-7K ohms (pull-down to ground)

Those levels are actually close to what you'd get out of most TTL outputs! It's not "RS232", but you can pretty much drive that directly from a PIC output pin.
I wouldn't do it for a real commercial product, but for a one-of you could probably get away with it.

Connecting to the TXD level from an RS232 output is a different story. There you have to deal with the fact that you might get as much as +/-25V levels on the pin.

[Charlie]

Folks don't get distracted by the schematic. This can work with that schematic, or with a piece of wire from pin 2 of the PIC to pin 2 of the DB-9. The transistor and it's support resistors are not really helping anything, but not really hurting either. The problem will be in the code, or possibly a bad PIC. I remember 12 bit cores don't like SEROUT2 but I'm not sure if this device is one of these?

[fratello]

Thanks for support !
As I say the schematic is fine (I think !) : http://www.picbasic.co.uk/forum/showthread.php?t=7182
Just my program is bad ...