404warehouse Jaeyoung Lim

1. USB2PPM Interface
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)
• adf

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. 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 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