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...and whack a stripped usb cable straight into a prototype board?

by bypass having to use an arduino I mean any kind of sheild? polulu would be perfect but im trying to avoid needing any of this.

My issue for finding tutorials and documentation on the subject is not quite knowing what keywords to search for, could someone point me in the right direction?

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  • Can you be more clear about what servos you want to control with what kind of signals? are you asking about just a shield no arduino? just the servos, nothing else? BTW just a stripped USB cable wouldn't have the USB to serial adapter built into most arduinos. Mar 10, 2015 at 6:23
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    USB is a non-trivial interface which involves fairly tricky signaling, so while you don't need an Arduino, you do need a USB-enabled I/O chip or microcontroller. There are indeed examples of such quite a bit cheaper than either an Arduino board, or even just the critical components on it which enable this functionality. Mar 10, 2015 at 12:55
  • yes thats it, the least amount of money needed to create signalling from usb with an outside powersource then? to be clear about hardware, I want to know if I can use output from computer programs nameley OSC so im not to bothered with details about servos specifically, just recieving data from dahn the usb cable Mar 10, 2015 at 19:09
  • by OSC, you mean the Open Sound Control protocol right? Mar 11, 2015 at 0:24
  • yeah, I understand it im controlling a program listening for osc and that program is sending commands based on the input to say, a prototype board or micro controller, as I understand it, dmx is appropriate protocol for robots but I just want cheap computer to robot interface Mar 11, 2015 at 22:14

2 Answers 2

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If I understand your question correctly you're asking if you can control servos with OSC and no microcontroller.
OSC is a protocol used for networking and communication between synthesizers, similar to midi in that, but totally different in the way OSC sends data which looks a bit like XML.

There's a couple of problems here:
1. Servos will not respond to OSC-signals. You could use MAX/MSP to generate servo-pulses from the OSC. The problem arises whan you are going to send this to the servos using usb.
2. USB, a fast data-transmission technology, is not suitable to be connected straight into a servomotor.

Arduino uses an atmega16u to transform the data from usb to serial (called a usb to serial programmer) for programming and communication. Then the microcontroller (atmega168/328) takes this and creates a pulse and a signal for the servo-motors.

To control servos without a micro-controller using USB is impossible.

It is be possible to control electronics using the serial-port and low-level coding. Used to do stuff like that on a Commodore 64 a time ago. Before these affordable, stable, reliable avr, arm and pic programming cards came out.

A tip: It is possible to load a program onto an atmega168/328 using a Arduino UNO or similar. Take the chip off of the programming card(ie. the Arduino UNO) and create a stripped down version, containing the micro-controller chip, 16kHz crystal, some capacitors and an usb to serial converter/ftdi-cable.

Regards
Krister Borge

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  • I wouldn't say it's impossible as there are USB-connected PWM generators, but a MCU would certainly be the best way. Mar 12, 2015 at 1:45
  • Ok, I see where you are going. It isn't impossible, just really hard. Most usb connected pwm generators has mhave mcus btw..
    – Faux_Clef
    Mar 12, 2015 at 6:11
  • Arduino does not utilize an FPGA. However, state-machine based logic such as is often implemented in a programmable gate array would be a way of controlling a servo (including a common PWM hobby one) from a USB host without utilizing a stored-program microcontroller. This is generally not done, because sufficient slices of programmable logic cost more than microcontrollers, and in a commercial-scale environment (such as an ASIC) tend to be a less flexible, and therefore more expensive, method. It is speculated that even most fixed-function USB interface bridges are MCUs inside. Mar 12, 2015 at 12:14
  • Uhm, you're right, it doesn't, my bad. I fixed it.
    – Faux_Clef
    Mar 12, 2015 at 22:04
  • Okay, understood. theres no point getting an arduino and pulling it apart so I will stick to traditional setup... Control a program with OSC on a PC and that PC will communicate with an arduino via USB and the Arduino program will turn that data into servo commands. Mar 14, 2015 at 11:08
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A build-your-own-duino isn't hard to do and it is quite inexpensive. It will make your life (or the part it you're about to spend creating custom hardware) much, much easier! I have built Joao Alves' CSE-duino for example and it has everything an UNO has except for:

  • on-board USB (use an FTDI cable that has USB <-> Serial in the cable head)
  • a 3.3v power supply; and
  • an ISP (high-voltage programming) connector;

, none of which you should need to drive a servo.

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