SparkFun According to Pete 4-4-11. Controlling an RC Servo with an FPGA. This time, we will look at how to control a regular RC hobby servo. They come in many different sizes and gearings, but for the basic control, they all use a simple PWM (Pulse Width Modulation) signal, to indicate the desired position. The width of the pulse should be between 1000 and 2000µs, with 1500µs representing the center position. Some brands have slight differences as to where the center point is, and some also allow pulses to be smaller than 1000µs and larger than 2000µs, but you can’t count on that. You also need to send a pulse to the servo at least every 20ms, otherwise the servo will likely enter standby, and it will no longer hold it’s position if there is a load on the arm. The implementation below is loosely based on the design described at fpga4fun.com, but instead of Verilog, I have decided to use VHDL. In addition to controlling the servo, I have tried to separate the project into multiple entities, as a preparation to expand with other controls.
Related posts: R/C Servos. R/C Servos FPGAs are suitable to control R/C Servos. What is an R/C Servo? An R/C Servo ("remote control servo motor") consists of a motor, some electronics, and a set of gears enclosed into a small box. A single axis comes out of the servo. Here's a picture of one servo (old and bitten up, but illustrates our purpose). Useful informational links include: R/C Servos are used in: In remote controlled models (cars, airplanes...).In robotics. Electrical connection and PWM pulses Servos have 3 wires: Black: ground.Red: power supply (+5V).White: rotation control (using PWM). A new pulse needs to be sent regularly (every 10 to 20ms), even if the angular position doesn't need to be changed, or the servo will stop trying to hold it.
PWM pulses from an FPGA Let's control a servo with an 8 bits resolutions (256 steps, from 0 to 255). Dividing the clock Using a 25MHz clock (40ns period), the first step is to divide the clock to generate a "tick" of period as close as possible to 3.9µs. That's all folks! LOGi-Bone. PTRobotics - Componentes para robótica e electrónica. Ps3joy/Tutorials/PairingJoystickAndBluetoothDongle. Description: This tutorial is an introduction to using the PS3 DualShock 3 Joystick connected via bluetooth to a desktop computer. After reading it, you should be able to bring up the ps3joy node and display the data coming from the joystick.
Keywords: PS3, joystick, driver Tutorial Level: BEGINNER Next Tutorial: Writing a teleop node Compiling Start by installing the dependencies and compiling the driver: $ rosdep install ps3joy $ rosmake ps3joy Pairing If this joystick has already been paired to this dongle you can skip this section and go directly to "Connecting to the Joystick Via Bluetooth".
For Computers with More than One USB Port Plug the USB bluetooth dongle into your computer. Load the bluetooth dongle's MAC address into the PS3 joystick using: $ sudo bash $ rosrun ps3joy sixpair You will see something similar to: Current Bluetooth master: 00:22:b0:d0:5a:09 Setting master bd_addr to 00:22:b0:d0:5a:09 Press Ctrl-D now so that you do not continue to run as root. Run the command: You will see: Micro Serial Servo Controller (assembled) Discontinuation notice: This product has been replaced by our newer Maestro USB servo controllers, which are better in almost every way. These older servo controllers are now only available by large-volume special order. Please contact us for more information. The Pololu micro serial servo controller (SSC) is a very compact solution for controlling up to eight radio control (RC) servos from a computer or microcontroller. The controller measures just 0.91" x 0.91", yet it is one of the most full-featured servo controllers available.
The micro serial servo controller is available in two configurations: fully assembled with all connector pins, as shown in the main product pictures, and as a partial kit. This servo controller supports two separate communication protocols. The servo controller is less than half the size and price of most 16-channel servo controllers.
Note: This product no longer ships with a printed user’s manual. People often buy this product together with: BeagleBone Black. What is BeagleBone Black? BeagleBone Black is a $45 MSRP community-supported development platform for developers and hobbyists. Boot Linux in under 10 seconds and get started on development in less than 5 minutes with just a single USB cable. Processor: AM335x 1GHz ARM® Cortex-A8 512MB DDR3 RAM2GB 8-bit eMMC on-board flash storage3D graphics acceleratorNEON floating-point accelerator2x PRU 32-bit microcontrollers Connectivity USB client for power & communications USB host Ethernet HDMI 2x 46 pin headers Software Compatibility Ångström Linux Android Ubuntu Cloud9 IDE on Node.js w/ BoneScript library plus much more BeagleBone Black Projects Android on Beagle Provides a stable Google Android base port for AM335x, AM35x, AM37x, platforms.
Ubuntu on Beagle Run the Ubuntu distribution on BeagleBoard (can extend to support BeagleBone, PandaBoard, etc.) Ångström Distribution Explore this Linux distribution tailored for embedded devices and shipped with the BeagleBone Black, BeagleBoard-xM and BeagleBone.