1 / 16

Network RC Car

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

gala
Download Presentation

Network RC Car

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. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Network RC Car Seth Schwiethale James Crosetto James Ellison

  2. 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)

  3. Camera’s Output • 1 “alarm” output • max activation is 100 times/sec (increments of 10 ms)

  4. 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

  5. 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

  6. Pulse Width Modulation camera’s output microprocessor car’s input

  7. 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!)

  8. Determining the Output Signal • Initializing the Pulse Width Modulator

  9. 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

  10. Setting the Period • The periods of both SA and SB need to be 20ms

  11. 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!

  12. Pulse Width Modulation Code

  13. 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)

  14. 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

  15. Interrupt

  16. Conclusion

More Related