Network rc car
Download
1 / 16

Network RC Car - PowerPoint PPT Presentation


  • 62 Views
  • Uploaded on

Network RC Car. Seth Schwiethale James Crosetto James Ellison. C ar’s I nput. square pulse of 1.0-2.0 ms, repeats every 20 ms It is the same for both steering and acceleration width of the pulse determines the direction/speed w / 1.5 ms as the nominal center

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' Network RC Car' - gala


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Network rc car

Network RC Car

Seth Schwiethale

James Crosetto

James Ellison


C ar s i nput
Car’s Input

  • square pulse of 1.0-2.0 ms, repeats every 20 ms

  • It is the same for both steering and acceleration

  • width of the pulse determines the direction/speed w/ 1.5 ms as the nominal center

  • the amplitude of the pulse is from the reference level of the Vcc (5v)


Camera s output
Camera’s Output

  • 1 “alarm” output

  • max activation is 100 times/sec (increments of 10 ms)


The problem
The Problem

  • Camera’s output can’t produce a 20ms PWM signal that is highbetween 1-2ms

  • Car cannot be driven by Camera directly

  • need something that modifies the output signal of the camera so it can be used by the car


The solution
The Solution

  • Using a microprocessor (MC9S12DP256)

  • has a clock signal rate of 24MHz

  • has registers for a Pulse Width Modulator and an Enhanced Capture Timer

  • Signal from the camera can be varied between 10-110ms for speed and 120-220ms for steering


Pulse width modulation
Pulse Width Modulation

camera’s output

microprocessor

car’s input


Pulse width modulator
Pulse Width Modulator

  • used to create correct output signal

  • uses CPU clock signal to generate signal lengths

  • current signal is 24MHz and we need a 50Hz (20ms) signal (Factor of 480000!)


Determining the output signal
Determining the Output Signal

  • Initializing the Pulse Width Modulator


Modifying the c lock frequency
Modifying the Clock Frequency

  • The pulse width modulator uses registers to decrease the frequency of the clock signal before it is used as an output signal

  • Two output signals can be generated from the clock signal

Allows for finer control of signal


Setting the period
Setting the Period

  • The periods of both SA and SB need to be 20ms


Setting the duty cycle
Setting the Duty Cycle

  • The duty cycle (the part of the PWM signal that is high) needs to be 1-2ms in length

  • Initialized to 1.5 ms

Notice the difference!



Enhance capture timer
Enhance Capture Timer

  • Used to trigger interrupts

  • Set up to trigger an interrupt every time a signal goes high or low on an input port (TCTL4 and TIE)


Counting
Counting

  • Timer Register (TCNT) is incremented every clock cycle (24MHz clock = 24 million times per second)

  • Clock slowed to 187.5 KHz

  • TCNT is 16-bit register (0-65535)

  • Overflows about every 1/3 second (65535/187500)

  • Never overflows more than once per input signal from camera


I nterrupt
Interrupt



ad