How to hook up two serial outputs to one serial input
February 10, 2010
So I'm working on a project where I'm using two processors and one of the things that I want to do is use one bluetooth device and have two microprocs communicate with it or send data through it. Of course this is not at the same time.
One chip would be the main com device, the other would send stored data when instructed to. I don't want to use one device as a passthrough as this would seem a little inefficient. so I came up with a schematic of what I think might work.
If anyone has tried this or can look at the schematic and say, yes this will work, here is why, or no, that won't work because your thingy is connected to another thingy that won't do what you think it should do.
The schematic should speak for itself in terms of how it works but a quick over is such.
npn transistor. base is connected to both inputs and this base input is also tied to v+ through a pullup resistor to keep the signal high(serial active low so high is idle)
collector is connected to V+
emmiter is connected to the input of the BT serial device with a 10k serial resistor.
the two picaxes are connected to the serial input line through 2 diodes that are reversed. The idea is that when one of the picaxes communicates it pulls the line low both pulling the base of the npn low and also pulling the second serial line low along with it.
One thing I'm looking at is where the base and the pullup meet. should I add a resistor at the point where the npn base and the resistor meets?
So again, does this make sense, do people think this will work....