-AT91SAM7X256 – Pulse Width Modulation YoonMo Yeon

Contents Speed control of DC motor Pulse Width Modulation AT91SAM7X256 PWM Controller & example

Speed control of DC motor Analogue type control Varying the voltage applied to motor Simple control circuit Heat problem (resister at voltage dropper) Low power efficiency at low speed Torque also varies Torque ∝ I V ∝ I ∴ It is not proper to vary the voltage

Pulse Width Modulation The average voltage applied to the motor is varied by switching the supply voltage very rapidly (ON/OFF) Duty Cycle

AT91SAM7X256 - PWMC PWM Controller Four channels, One 16-bit counter per channel Common clock generator providing 13 different clocks 11 : One modulo-n counter 2 : Independent linear dividers working on modulo n counter output

Set up the PWMC in your Application

PIO & PWM lines 4 Multiplexed Channel outputs with PIOB lines

Set up the PWMC in your Application

Enable the PWM Clock Clock of peripherals Power Management Controller controls the clocks of each embedded peripheral The peripheral clocks are automatically disabled after a reset

Set up the PWMC in your Application

Set up the Clock Generator Per each channel Channel Mode Register Duty Cycle Register Period Register Counter Register Update Register

CMR = 10 -> CPRE = MCK/1024 CPOL = 0 : start at low level CALG = 0 : left aligned CPRDR = > CPRE / > MCK / 1024 / 1024 ≒ 48Hz CDTYR = 256 -> Duty Cycle = CDTYR / CPRDR -> D = 256 / 1024 = 1/4

Set up the PWMC in your Application

Channel Enabling

Modify a channel period/duty cycle In running mode, modifying the duty cycle or the period value can be done only via PWM_CUPD

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