Can I have 2 Props on 1 Eddie

smithdavidp

I ordered my Eddie last week and I have been studying the sensor layout. I have come to realize that the Eddie platform has no sensors in the rear as compared to the Medusa which has sensors all the way around. If I have read the documentation right there will only be 7 multipurpose pins left when the Eddie controller is connected. My thought is to purchase 3 of the dual sensor brackets (Ping/IR) and 6 IR sensors. The three ping/IR brackets would be placed in the rear and the 6 IR's would be placed on the bottom to avoid dropping off of a cliff. If I do this then there is no possibility that the Eddie controller could handle the extra inputs. Is it possible to connect another Prop to the Eddie controller or in lieu of that connect it to the PC? Is this even necessary? I know that the Kinect has 3D imaging but it doesn't rotate. The whole Robot has to turn. And If I'm not mistaken the Kinect has a blind spot in front of the Robot. If this was a drop off the Ping, and the IR could not see it and the Robot would take a plunge. The Eddie platform should be here tomorrow. HP won't be shipping the PC until the 15th of May so I still have some time to get any extras ordered before I start getting everything hooked up.

Duane Degn

Dave,

There are a bunch of different options for increasing the Propeller input and output capability. Adding a second Propeller is one of those options.

There are lots of multi-Propeller projects around.

I use this stack of Propeller Proto Boards in my Meacanum wheeled robot.




The top board controls the motors, monitors the encoders and interfaces with the wireless transceiver.

The bottom board captures images from a video camera and drives an array of 120 LEDs.

Adding a second Prop introduces some challenges. You need to use some sort of protocol so the Propeller can communicate with each other in a meaningful way.

While adding a second Propeller is an option, there might be ways of sharing IO pins with your planned set up. You might want to wait until you have your robot working with one Propeller before adding a second.

There are also chips available to increase both output pins and input pins. I don't have a lot of experience with these chips other than 595 shift register.

Since I have experience with these chips I'll give an example of what they can do.

As I mentioned, the bottom board in the above photo controls an array of 120 LEDs. Obviously I didn't have 120 Propeller pins to turn the LEDs on and off. I used a stack of 595 shift registers to drive the LEDs. Each shift register has eight output pins. It takes four Propeller pins to control the shift register but these shift registers can be daisy-chained so four Propeller pins can easily control lots of LEDs or other devices requiring a logic high or low state.

While I could have controlled all 120 LEDs with four Propeller pins and 15 shift registers, in order to have the LEDs update faster I used two sets of 8 shift registers and used one more Propeller pin (for a total of five) to send data to this second stack of 595 chips.

This is one example of many possible ways of expanding the Prop's I/O ability.

But again, I'm not sure if you should worry about this yet. I'm pretty sure you could add a way of detecting a drop off with a single Prop.

One option would be to mount your sensors on a servo to scan an area rather than using multiple sensors. Even if you do use multiple sensors, you could have them share pins.

Sorry for rambling, it's past my bedtime and I don't think I'm thinking straight.

smithdavidp

I guess I'll just have to wait until I have everything under 1 roof. I do have the Prop BOE to experiment with once everything is assembled. Like I said earlier HP is dragging their feet because I spec'd out the notebook that I want to use on this project. It wasn't somthing they could just pull off the shelf. The anticipation of getting everything here is killing me. My understanding is that the lower functions are controlled by the Propeller controller while the upper functions are controlled by the PC. I take this to mean that it is the PC that makes the decision on where to go and what to do. My specifications for operation of my project has not changed. So there are a few other sensors that I want / need to install. The Kinect has a built in accellerometer but no compass. I plan to install a compass and a temperatue sensor into Vhal (pronounced Val as in Valerie). Yes..... I already have a name for it. [V]eterans [H]ealth [A]ssesment [L]ink. Unless I make my own circuits it would be easier to incorporate a Prop BOE and just breadboard the sensors that I need. Parallax has provided me with 6 servo pins which could handle the IR sensors. Pins 14-19 would then be gone. The Ping / IR combo sensors would then take up pins 8-13. Pins 1-7 would be used for the Temperature, Compass, and possibly PIR sensors making the Prop BOE pretty much an information center that gives the PC more data thereby having less motion errors and giving it the ability to report its environment temperature, map the area it operates in, and enhances its ability to sense intruders. How to get there, from here, is the question. At first I thought that I would interface the Prop BOE in the same manor as the Eddie Prop controller using that controllers handshaking signal program as a map for the Prop BOE. I am guessing that the Prop controller interfaces via serial USB. The PC I ordered has 3 USB ports. One of which will have to live with a USB hub plugged into it. The timing and Cog usage comes into play no matter what direction I go in. It is my fear that marrying the Prop BOE to the Prop controller would then make the timing extreamly criticle. I don't have the Microsoft RDS4 software yet so I don't know how it handles the serial data or if it will even accept the presence of a second Micro Controller. The idea of putting the sensors on servos seems to be a sound solution to the backing up issue. I believe that the new Ping / IR bracket will mount on a servo and then a 180 degree scan of what is behind the Robot could be achieved with the assembly mounted in the center of the lower deck thereby eliminating 4 sensors (2 ping and 2 IR). It may be as you say. I should wait to have a functioning base, to work from, and then go from there. I am beginning to wonder if I couldn't claim Parallax as a dependent next tax year. lol

Mike G

The IR sensors require an A/D. The MAX1112 has 8 channels controlled by 4 I/O.

RobotWorkshop

On the last couple robots I built there are a pair of Propeller boards embedded in the robot. You'll want to determine if the second Propeller board is going to talk directly to the Eddie board and all the data flow back through that back to the PC or if you just want each board to talk directly to the PC. You can do either one.

If you are running low on USB ports or if the project just has multiple Propeller boards I usually embed one of these USB hubs in my project:

http://www.amazon.com/Targus-ACH63US-Super-Mini-4-Port/dp/B0009TQB1O

Since I power the Propeller boards directly and not through the USB I am able ti use this as a passive hub and don't have to power it separately.

Each of the Propeller boards will show up as a unique COM port on the PC so you can open a couple instances of the Prop tool and program each one through a single USB connection to the computer.

Robert

smithdavidp

I think that is my answer then. There is no need for the Prop Boe to directly access the Eddie Prop Micro Controller. The additional Props only function is to give additional data to the Eddie PC for navigation and Invironment purposes. I have two hubs. One is a slim, mini 2.0, and the second is a Belkin with a swirchable power supply. Either external 5v or internal usb supplied power. Both have 4 ports. I will be using 4 ports for Medical test equipment and that leaves me with two open ports for the Props. Don't think they are awake over at Parallax yet but when they get there they will have another order waiting lol.

RobotWorkshop

I've been using the passive hubs whenever possible but I do have one large robot where I had to use a powered hub. Most of the powered USB hubs require a 5V supply I just ordered a DC/DC convertor module that will take the 12V battery voltage and generate a dedicated 5V supply for the HUB. There are some hubs for industrial and automotive use that will run from a 12V supply but those weren't as common and most were a lot more expensive.