What's the best way to wire Prop to Prop communications for a serial object?
ElectricAye
Posts: 4,561
I'm interested in using Kye's Full Duplex Serial Port Driver to have one Prop talk to another, but I'm wondering what's the best wiring for this. I've seen people mention placing 2.2 K resistors in line with the connections and other people using 10K pullups to Vcc without said series resistors, so I'm a little bit baffled by what's the best method.
http://obex.parallax.com/objects/397/
Thanks.
http://obex.parallax.com/objects/397/
Thanks.
Comments
Theoretically, you could just connect one set of Propeller I/O pins to the other. In practice, people make programming errors and it might be possible that you'd designate the wrong I/O pin to be an output and it would be connected to the other Prop's output pin. Fortunately, the Prop is fairly robust and that would not likely damage the Prop, but it could and it's not a good thing to do. A 220 Ohm resistor is enough to protect the output I/O pins from damage in this sort of situation. The 2.2K resistor is used when the voltage on the I/O pin can go higher than 3.3V, usually when connecting 5V logic signals, like from a sensor, to a 3.3V logic Prop I/O pin.
The 10K pullup is intended to provide a known signal to the Prop input I/O pin when the other Prop is not initialized first or when the 2nd Prop is somehow disconnected (unplugged). That's all.
@Kirk,
Say more about what you want to do ...
I want to connect 10 Props, collect one POT position from each of 7 cogs, send them to a PC, receive position commands, send them to the appropriate Prop and process them into PWM signals in their cogs to make a robot. Hopefully the FDComm object can run in one cog.
It would be nice if the USB of either Prop-PC or PC-PC could be done wirelessly.
Kirk
Cool, that works for me. Thanks very much!
You're talking about a complex system. If you want suggestions, you're going to have to give more information first. For example, what are the pots for? How are the 7 pots distributed over the 10 Props? Why is each pot associated with its own cog? Which Props / cogs are supposed to generate PWM signals? What's the PWM used for? Remember that there are objects that can generate PWM signals and servo control pulses particularly on multiple I/O pins and use only one cog. What kind of information is supposed to go from Prop to Prop? from Prop to PC and back? Are you looking to connect everything by wireless or just a Prop cluster to/from a PC? What kind of wireless? What range? What kind of data volume? speed?