Configuring pin 16 integrating with wireless modem.

Robert Gray

I'm trying to integrate a XBEE wireless modem directly with the sin pin and sout pin. I'm sending data at 9600 baud 8N1. When I analyze the sout pin it looks as if the data is being sent inverted, in other words the line is held low and until the data starts. I tried using the different configurations for the serout command and the data still comes out the same way, inverted. Is there something special about these pins that the data cannot be sent true instead of inverted?

allanlane5

Yup, the "pin 16" has a special thing that it ignores the "Inverted" signal -- I don't know why. The hardware also 'echo's everything out RX that gets sent in to TX, so that too is a problem.

It MIGHT work with the TTL levels that the BS2 can already generate, you might just try it. Put a 22 KOhm resistor in series with the recieve line, though.

Robert Gray

Thanks for the response, I think I'm going to put an inverter circuit.

allanlane5

Here's a question, though -- why would the XBee WANT a signal different from what a PC would put out? Because that's the signal the 16 port puts out.

Note it uses the incoming 'TX' voltage, and modulates that with the RX signal going back. So if the XBee is not sending a good -10 volts, the BS2 can't 'modulate' that to +5 to send the signal back.

Now, if you use a MAX232 inverter circuit, then you can connect the XBee to any two BS2 pins (one input, one output) that you like.

Bruce Bates

Robert -

If you add an inverter circuit at the PBASIC Stamp level, I doubt you willl be able to program the Stamp any more. The two solutions to this are:

1. Use a pin port other than pin port 16.

2. Build the inverter circuit at the "far end" (at the other end of the communications link) so that if it's removed, pin port 16 will be as it originally was.

Regards,

Bruce Bates

Post Edited (Bruce Bates) : 4/5/2007 8:54:05 AM GMT