USB2PPM Interface

Jaeyoung Lim

Blog post related to the slide can be accessed here

Summary

  1. USB2PPM Interface by Jaeyoung Lim
  2. Contents

– Overview
– Need Finding
– Problem in current works
– Wiring
– Software
– Firmware
– PC Interface
– Projects
3. Overview
– USB2PPM is a device that can translate serial or voltage command values and encode it into a PPM(Pulse Position Modulation) signal. The signal is sent to the trainer port of Turnigy 9X to be transmitted over radio signals USB2PPM Features
– Low latency ( 50Hz or 20ms)
– Long Range control ( >2km )
– Resolution : 0 ~ 1150 – Simple / Low cost components
– Able to switch commands from potentiometer(voltage inputs) to Serial inputs
– Developed as an Arduino UNO Shield
4. Need Finding
– Radio Control as a control method
– Serial inputs require complex interfaces to use – Accessing serial ports through software is compex – Needs a spare UART Port for the system to control – Usually short range
– Serial Communications have latency issues – Xbee communication speed reduces when communicating both ways – Streaming Wifi requires a high performance computer(usually PC)
5. Wiring
6. Software (Firmware)
– Total length is 2200 μs – Minimum command value is 650 μs – Maximum command value is 1700 μs TCCR1 : Timer Counter Control Register TIMSK : Interrupt Mask Register TIFR1 : Timer Interrupt Flag Register OCR1 : Output Compare Register
7. Software (Firmware) Problematic Software – Solved the problem using variable interrupts
8. Software (PC)
– Uses USB cable to connect with Arduino
– Encodes PPM command values into a string “x1023y1z43k923”
9. Designs
– Design A: USB2PPM System
– Low latency (50Hz)
– Simple Architecture
– Long Range
– Trimming Issues
– Dependent on dynamic characteristics
– Design B: ROS System
– Offboard Control
– Kinematics / Force Control
– ROS Compatible
– Complex Software
– Latency Issues from MAVLink Serial Comm. System Layout Usb2ppm for quadcopter Control
10. USB2PPM
– 4 Channel PPM commanded from USB
– Resolution: 1024
– Needed for Trimming Quadrotor before flight
– Arming Switch for Experiment – PPM Interface with Turnigy 9X USB2 PPM PPM UARTGCS Potentiometer

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