USB2PPM InterfaceJaeyoung Lim

Contents• Overview• Need Finding

• problem in current works

• Wiring• Software

• Firmware• PC Interface

• Projects

OverviewUSB2PPM 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

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)

• adf

Wiring

Software (Firmware)

• Total length is 2200 μs- Minimum command value is 650 μs- Maximum command value is 1700 μs

TCCR1 : Timer Counter Control RegisterTIMSK : Interrupt Mask RegisterTIFR1 : Timer Interrupt Flag RegisterOCR1 : Output Compare Register

Software (Firmware)

ProblematicSoftware

- Solved the problem using variable interrupts

Software (PC)

• Uses USB cable to connect with Arduino

• Encodes PPM command values into a string

“x1023y1z43k923”

Design A: USB2PPM System

Pros - Low latency (50Hz)- Simple Architecture- Long Range

Cons - Trimming Issues- Dependent on dynamic characteristics

Design B: ROS System

Pros – Offboard Control- Kinematics / Force Control- ROS Compatible

Cons - Complex Software- Latency Issues from MAVLink Serial Comm.

System LayoutUsb2ppm for quadcopter Control

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

PPMUARTGCS

Potentiometer