Steering Servo How to control the car heading via a steering servo

Team: //noComment

Leader : Christian

Software Specialist : Matt

Hardware Specialist : Vic

Assistant : Andrew

Overview Hardware

Futaba S3010 Specs Components Needed Wiring

Interfacing

Registers Used Register Diagram

Analog to Digital Conversion PWM Review

Mechanical Binding Test Software Implementation Summary References Questions

HardwareFutaba S3010 Servo (1)

Futaba S3010 SpecsControl System: +Pulse Width Control

Required Pulse: 3-5 Volt P-P Square wave

Operating Voltage: 4.8-6.0 Volts

Operating Speed (4.8V): 200 ms/60 degrees at no load

Operating Speed (6.0V): 160 ms/60 degrees at no load

Pulse Span: 1000-2000usec

Dimensions: 1.6” x 0.8” x 1.5”

Weight: 1.40z (41g)

Components Needed 32 bit ColdFire MCU FireBird32

Smart Car chassis with mounted Futaba servo

Bench Top Power Supply(5v)

Jumpers

Oscilloscope

Potentiometer

Wiring

Powering the Servo Connect 5V from power supply to the RED pin on the servo

connector Tie the grounds of the ColdFire and the bench top supply

together Connect the BLACK ground pin from the servo to the Coldfire

ground

Connecting to Coldfire Connect WHITE control pin from servo to Coldfire PWM output

port (PF4)

Interfacing

MCU(Coldfire)Servo

PowerSupply (5V)

Registers Used

TPM2SC – Status Control RegisterTPM2MOD – Modulo Register (sets period)TPM2C0SC – Channel Status and Control RegisterTPM2C0V – Value Register (sets pulse width)

Register Diagram

Register Diagram

Analog to Digital ConversionInitialization Select ADC clock source and divide by # bits for conversion

(ADCCFG)

Per Conversion Select channel to convert (ADCSC1) Wait for conversion complete (COCO) Read data from result registers (ADCRx)

Analog to Digital Conversion//derived from Prof Sumey

int adcGet() //adc conversion on PTB4, 10 bit thus 0-1024 result, result then returned

{

//channel 0=PTB0... channel 7=PTB7

//channel 8=PTD0... channel 11=PTD4

// perform conversion

ADCSC1 = 4;// start conversion on PTB4 , channel 4

while (!ADCSC1_COCO){} // wait for conversion complete*

return ADCR; // grab 2-byte result and return it

}

void adcInit()

{

// ADC initialization:

ADCCFG = (0b10 << ADCCFG_ADIV_BITNUM) // select Busclk/4 (3MHz)

+ (0b10 << ADCCFG_MODE_BITNUM); // 10-bit mode

}

PWM Review

MCF51JM128 ColdFire® Integrated Microcontroller Reference Manual

Mechanical Binding Test

NO

YES

FOREVER {adcresult = adcGet();dir(1000+adcresult);}//Max=1777us//Min=1134us

Software void initializeMCU() {

…..

//SOPT2_CLKOUT_EN = 1;…..

}

PWM initialize()

TPM2SC = TPM2SC_CLKSA_MASK // select bus clock for timer clock

+ 8;

// divby-8 prescaler (8MHz / 8 = 1MHz Timer clock)

TPM2MOD = 10000; //Period = 20,000us= """20ms"""= f=50Hz

TPM2C0SC=0x38; //Set status control register

TPM2C0V = 1500; //Pulse Width = """1.5ms""“

*TPM2C0V*

Summary

How to control the car heading via a steering servo

References (1) “S3010 Std. HT Ball Bearing." S3010 Std. HT Ball

Bearing. N.p., n.d. Web. 17 Feb. 2015

(2) “How Do Servos Work?" How Do Servos Work? N.p., n.d. Web. 17 Feb. 2015.

(3) "Futaba S3010 - Standard High-Torque BB Servo." Futaba S3010 Servo Specifications and Reviews. N.p., n.d. Web. 17 Feb. 2015

Questions?