Hooking two propellers together

agimuhing

How do you hardwire two propellers together?


I plan to have the chips on the same board

I want to build a quadrotor, but one propeller chip doesn't have enough I/O pins

Timmoore

The simplest way is to connect the 2 using a serial port. A lot depends on what you are running on each and the interaction between teh 2 - how much and how frequenctly the 2 props need to communicate. e.g. I have 2 props connected for 1 quad the 2nd is for a video overlay it uses a serial port and just updates the parts of the overlay that changes everything else is on the other prop.
What are you using all the pins for? I have built a quad using the prop and tend to run out of cogs before pins.

wjsteele

Simply tying a single I/O pin is the minimum you need for them to be able to communicate. However, you'll need to be more specific as to what you're trying to do for us to be more help.

With that said, there are several communication mechanisms available for Prop to Prop communication. I'd start out by figuring out what your requirements are, for example, speed and/or protocol requirements. Then head over to the OBEX and see what has already been done.

If you use a single pin, you'll get the slowest performance, but also the simplest solution, but adding more pins/cogs can get you mind numbing speeds. :-)

On a quad rotor, the single pin solution might be enough, plus it will give you the most available free i/o pins. Using the single wire solution will also only take one cog (or less using some cool coding techniques, like multi-threaded serial) on each Prop.

Hope that helps!

Bill

Toby Seckshund

Beware if you are tempted to use just the one xtal, as I did once. All seemed ok with powering up and both being reset together but when the "Master" Prop (which was supplying the "Slave" clock) got a reset separately the "Slave" crashed, as the "Master" kicked off again but in RCSlow mode leaving the "Slave" clockless.

jmspaggi

Hi Toby,

Does it mean the slave will crash? Or it willgo slower for few cycles?

JM

Humanoido

Hi Agimuhing,

There should be no problem communicating serially using a one wire interface and a single resistor, with two props, each having their own crystal. When you run into larger sets of props interfaced that require multi-loading, the timing (and supply) become more critical and must be handled differently. There's a single wire bit-banging object in the OBEX. You can wire up two props on a breadboard in five or ten minutes. When you get everything working, be sure to enter your project into the Multiprop Forum list thread.

http://forums.parallax.com/showthread.php?t=124172

Humanoido