Why Use the parallax propeller? (quadcopter)

Mauvai

What are the advantages of using a Prop over something like a beaglebone, or a Pi/arduino combo? Issues like pricing are obvious, but does the the prop have any discrete advantages, and vice versa?

Mark_T

"discrete advantage"? As opposed to a continuous advantage?

Anyway the prop chip can be viewed as a bunch of interface hardware that happens to be implemented in software,
so its not limited to any particular set of hardware peripherals, any pin(s) can be assigned to any task, within the limits
of the architecture - you want another couple of I2C drivers, just change the code...

So its a good match to adapting a wide range of microcontroller tasks without having to worry about mixing/matching
pins/peripherals.

If you want heavy lifting its only a 32 bit integer microcontroller (or rather 8 of them in one chip with shared memory).
You want to do some vision processing, its not got the grunt or anything like enough RAM. But then again it doesn't
need an operating system, there's hardware locks and a central hub to give you synchronization when you need it.

You could view it as a glorified I/O expander, or as a complete system driving a simple GUI on a VGA screen.

As a for-instance there's nothing in the design aimed at supporting an I2S digital audio bus, but give it a 6.144MHz
crystal and you can program it to talk I2S because its got enough flexible hardware support and completely cycle-accurate
determinism.

LoopyByteloose

I would have to say that the Propeller is just going to offer more a simple, direct solution to operating a quadcopter. Code is for one device that doesn't require an OS or file system.. more compact and more directly applied.

BeagleBone is a Linux SOC, so you have to deal with the added complexity of an OS and file system.
The Raspberry Pi with Arduino, also is a Linux SOC, but you had added yet another layer by including an Arduino.

Both the BeagleBone and the Raspberry Pi may just be more architecture than you really need for a quadcopter. You certainly will consume more power than just using a Propeller.

Of course, if you are making your choice based entirely on just borrowing working code for a BeageBone or a RaspberryPI/Arduino solution -- it is easiest to stay with the platform the code was intended for.

Mauvai

Thanks Guys. I was always pretty sure we were going with the prop, but its nice to get advice. We have no intention of having to deal with writing an OS and all the related stuff

ValeT

Having 8 cores for that price should be all the reasons you need to buy and use the Propeller micro controller.

Then again, the 16 cores that the Propeller 2 provides is definitely a lot better. Too bad that's not out yet .

tonyp12

I could see that using 4 cogs just to monitor and adjust motor speed without fear of an interrupt is busy right now, as could happen to those other mcu's.
Though most Parallax motor driver solutions I seen seems to use 1wire pwm signal to a generic 3phase driver board, less of the instant response than could been had.

Mauvai

If we really do need 16 cores, a second prop chip for $8 is really not all that bad I have been doing a review of as many options as i could find, All the linux based systems are too slow, and i dont know of any micro with more power (that also has a decent level of support)

kwinn

For controlling something like a quadcopter the propeller is definitely the best choice. No issues with interrupts or control signal timing.

LoopyByteloose

Several years ago, I got into studying Real Time Operating Systems for robotic control. Tons of material has been written on RTOS and there are cases where it does add some. But these cases seem to apply to where Real Time solutions are needed on a large network; e.g., airline ticketing, package delivery logistics, high speed rail management.

And so, it became obvious that Real Time Without Operating Systems often out-performs in situations where you have a single operator. And in that case, parallel processing rocks.

Admittedly, limitations in terms of Cogs or total Hub ram can create barriers. Though it seems the quad-copter code can fit into one Propeller 1. Think of the Propeller 2 as a barrier-breaker. The addition of ADC and DAC is a big boost as well as more Cogs, more Hub ram, more i/o.