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Thread: Discussion of Microprocessors

  1. Discussion of Microprocessors

    So what microprocessors are best for an embedded control system (not necessarily including piloting)? I have heard a little about arduino and that's about it. I am inclined to think the atom chipset might be a more powerful solution, but I don't know a lot about EE and CS. So I was hoping for some suggestions. I will put a list of what we discuss on this post too if people would find that helpful.

    Thanks in advance.

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    Re: Discussion of Microprocessors

    A lot of it is going to depend upon what you're comfortable coding in. What languages are you proficient in?

    I'm using a Basic Atom in one mech (basic), and a Gumstix in the other (linux w/ C)

  3. Re: Discussion of Microprocessors

    I am completely proficient in MATLAB, Basic, and NQC. It wouldn't be a stretch for me to pick up most codes and I am not limited to merely my own limited capacities .

    Also, is the basic Atom the same as Intel's atom?
    Last edited by Firestorm65; 02-02-2009 at 01:13 AM.

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    Re: Discussion of Microprocessors

    First off, there's a huge difference between a microprocessor (intel Atom) and a microcontroller (Basic Atom).

    For the sake of simplicity, let's say a microprocessor is what's inside a computer, which is basically no more than an ALU (arithmetic and logical unit) and an instruction decoder. All it does is decode an instruction, execute it, and fetches the next instruction.
    It needs RAM, a BIOS (ROM), and you'll probably want some input/output to get it to do anything usefull, like a keyboard, mouse, and screen.

    A microcontroller can be viewed as a computer-on-a-chip, once again, for the sake of simplicity.
    The ALU is now slammed with RAM, ROM, input/output and a lot of peripherals on the same chip.

    What this means is, you can use a single chip to control a robot, communicate with your cellphone, read GPS data, etc etc etc.

    That being said, there's a practically infinite amount of microcontrollers out there.
    Microchip, one of the bigger microcontroller suppliers, has a few hundred (if not thousand) of their own.

    Biggest differences in microcontroller world are the sizes of the databus.
    8-bit, 16-bit, 32-bit controllers. The bigger you go, the more they're capable of working with large computations.

    For example, an 8-bit microcontroller has a hard time calculating 1245.4 * 1457.2, while for a 32-bit controller this could easily be only one instruction.

    Controllers are usually based on a 'core', meaning there's a bunch of different ones, each with the same 'core' microprocessor, but with a variety of ram/rom/peripherals.

    The most popular cores today are 8052 (8-bit), AVR(8-bit), PIC(8 to 32-bit, though the cores vary along the series), and ARM(32-bit)


    I can go on and on with this story, but the point was, uhm.. I don't remember

    Anyway, there's a lot of choices, but as a complete beginner I would advise to start somewhere simple, other people will most likely give you better advice on this, since I only use "back to basics" controllers and have no experience with something like a Basic Stamp.
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  5. Re: Discussion of Microprocessors

    So which is better for a mech? If I want to do all of the balance and visual tracking algorithms onboard, wouldn't the microprocessor have more potential? Intel Atom runs at 1.6 Ghz; how fast do microcontrollers run? Also, wouldn'y a full OS like linux be easier to program and communicate with? I honestly don't know.

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    Re: Discussion of Microprocessors

    As has been said : microcontrollers have peripherals that are not available on microprocessors. Specific tasks are best handled on one device or the other.

    For balance, this would be best done in a microcontroller, as it has more direct access to reading the PWM or analog signal from an accelerometer and gyro sensors, so to be able to quickly (in real time) provide a reactive drive to the motors actually balancing the robot.

    For visual tracking, a microprocessor more easily handles the processor intensive video analysis.

    Microcontrollers can run anywhere from 4 MHz to 80 or more MHz, not typically in the GHz range.

    Microprocessors don't have ADC inputs, timer inputs, PWM outputs, SPI interfaces, or even basic digital IO to read the state on one pin, like microcontrollers can. Therse things can be hacked on to a microprocessor, but usually that involves some sort of microcontroller helping out, and typically the OS for the microprocessor gets in the way of the real time responses needed to these signals.
    Last edited by robologist; 02-02-2009 at 06:50 AM. Reason: mistake

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    Re: Discussion of Microprocessors

    If you want to do onboard visual tracking, you are probably gonna need something fairly powerful - since I'm assuming you want to use a webcam == processor needs to be a USB host. There aren't that many embedded processors with true USB host ability out there. I believe that the USB host requirement rules out the gumstix boards.

    Walking robots have light payloads, that camera, your guns, etc are gonna add up fast, so your processor has to be lightweight, and low power, since more power equals more batteries equals more wieght. Additionally, you only have so large of an area to mount the thing, so something like a mini-ITX is out based on size (even if we forgive power req's).

    Since we ruled that our board has to be low power, lightweight, small, and have a USB host -- I think we are squarly at Pico ITX as one of our view options. It might also be possible to use something like the blackfin + camera combo here: http://www.trossenrobotics.com/surve...in-camera.aspx

    If you go the PicoITX route.. you'll still need something to control the robot, and that means a micro, such as the Arduino or Axon, or anything else that has real ADC and PWM.

    Quite frankly, if you don't know the difference between a Basic Atom and an Intel Atom, I'd skip the visual tracking req's right now, and get SOMETHING working using and AVR or a PIC. If you can't drive around, it doesn't matter if your mech has visual tracking.

    -Fergs

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    Re: Discussion of Microprocessors

    Fergs give good advice here. My recommendation is to use a microcontroller and get the thing walking. Use a laptop to control it and receive the video wirelessly. This is the scheme that most people (with a few exceptions) will be using.

    The key and the hardest part is to get it walking and working under your control.
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  9. Re: Discussion of Microprocessors

    I'm not the EE guy on my team, so excuse the possibly naive questions. My knowledge is pretty sparse outside of CS; I happen to be an AE major.

    So a pico-itx allows for atom, but I could see as large as mini (~6"x6") with an E5200 if placed intelligently. Even without visual recognition, it seems like a microprocessor would allow more intelligent gaits, as well as "run" or "walk" modes. A 30g battery could power the processor for for twice as long as the machine is expected to run (15 min), so it doesn't seem outrageously heavy, especially with stronger servos.

    So assuming I get it to fit, can a microprocessor control everything onboard? Would it need a microcontroller just to talk to the motors?

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    Re: Discussion of Microprocessors

    Quote Originally Posted by Firestorm65 View Post
    I'm not the EE guy on my team, so excuse the possibly naive questions. My knowledge is pretty sparse outside of CS; I happen to be an AE major.

    So a pico-itx allows for atom, but I could see as large as mini (~6"x6") with an E5200 if placed intelligently. Even without visual recognition, it seems like a microprocessor would allow more intelligent gaits, as well as "run" or "walk" modes. A 30g battery could power the processor for for twice as long as the machine is expected to run (15 min), so it doesn't seem outrageously heavy, especially with stronger servos.

    So assuming I get it to fit, can a microprocessor control everything onboard? Would it need a microcontroller just to talk to the motors?

    No problem, we all start somewhere

    Problem you're going to run into with anything aside from a pico is going to be power requirements. The pico-ITX boards generally have pretty low power consumption, especially the 500mhz ULV version. Mini's have a considerable jump in power draw, so much that it's really not feasible for a walker given the extra batteries you would need to get it to run for even 15 minutes.

    You also have payload to consider. Believe me, I tried to see if I could fit a 500mhz pico on a biped using standard type servos, and once you start adding the supporting peripherals together it adds up QUICK! I abandoned the plan and went with a microcontroller for the main 'brain'. To put it bluntly, you'll need a minimum of $2400 worth of servos (12x RX-28s, for a biped), not to mention a good cost on machining your own brackets for them, to feasibly consider using a pico onboard.

    You'll also still need some sort of 'bridgeware' such as a microcontroller or other interface to control your hardware. As stated above me, computers don't come with the hardware interfaces that microcontrollers do. You have no way of controlling servos, reading sensors, or even controlling your bot without a considerable lag without external supporting devices to handle that interface for you. And those extra devices mean even more weight, and even more power consumption.
    Last edited by DresnerRobotics; 02-02-2009 at 09:02 AM.

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