microcontroller - AVR PWM 配置

Question

我知道这很愚蠢，但我真的很困惑。

我想在 Atmega16 上制作具有 3 种模式的 PWM 脉冲： 1- 1Khz 占空比 100% 2- 4Khz 占空比 100% 3- 1Khz 占空比 50%

我离开 AVR 快 2 年了，我忘记了一切，所以我只需要简单地计算 Timer 1。我读过的任何东西都让我更加困惑。有什么可以帮助我的吗？我正在使用 Codevision AVR。

Answer 1

1- 1Khz with Duty cycle 100%

2- 4Khz with Duty cycle 100%

are the same thing. There is no actual PWM at all. The output is high all the time and frequency doesn't matter.

3- 1Khz with Duty cycle 50%

is actually PWM. There are a few types to choose from, but if the duty cycle is going to be exactly 50%, then there are easy ways to achieve this with a toggle. From the manual,

A frequency (with 50% duty cycle) waveform output in fast PWM mode can be achieved by setting OC1A to toggle its logical level on each compare match (COM1A1:0 = 1). This applies only if OCR1A is used to define the TOP value (WGM13:0 = 15).

That is, set the COM1A1 and COM1A0 bits of TCCR1A to be 01, and set all the WGM bits of TCCR1A and TCCR1B to be 1. Choose OCR1A and the CSx prescalar bits of TCCR1B so that OCR1A is reached every 0.5 ms.

Answer 2

我这样做了，但是我有考试，所以发布它的时间太长了。我将 Fcpu 设置为 4MHz

这是代码：

void set1KhzDC100()
{
// Timer/Counter 1 initialization
// Clock source: System Clock
// Clock value: 500.000 kHz
// Mode: Fast PWM top=0x01FF
// OC1A output: Non-Inv.
// OC1B output: Discon.
// Noise Canceler: Off
// Input Capture on Falling Edge
// Timer1 Overflow Interrupt: Off
// Input Capture Interrupt: Off
// Compare A Match Interrupt: Off
// Compare B Match Interrupt: Off
TCCR1A=0x82;
TCCR1B=0x0A;
TCNT1H=0;
TCNT1L=0;
ICR1H=0x00;
ICR1L=0x00;
OCR1A=511;
}

void Set4KhzDC100()
{
// Timer/Counter 1 initialization
// Clock source: System Clock
// Clock value: 4000.000 kHz
// Mode: Fast PWM top=0x03FF
// OC1A output: Non-Inv.
// OC1B output: Discon.
// Noise Canceler: Off
// Input Capture on Falling Edge
// Timer1 Overflow Interrupt: Off
// Input Capture Interrupt: Off
// Compare A Match Interrupt: Off
// Compare B Match Interrupt: Off
TCCR1A=0x83;
TCCR1B=0x09;
TCNT1H=0x00;
TCNT1L=0x00;
ICR1H=0x00;
ICR1L=0x00;
OCR1A=1023;
OCR1BH=0x00;
OCR1BL=0x00;
}

void Set1KhzDC50()
{
// Timer/Counter 1 initialization
// Clock source: System Clock
// Clock value: 500.000 kHz
// Mode: Fast PWM top=0x01FF
// OC1A output: Non-Inv.
// OC1B output: Discon.
// Noise Canceler: Off
// Input Capture on Falling Edge
// Timer1 Overflow Interrupt: Off
// Input Capture Interrupt: Off
// Compare A Match Interrupt: Off
// Compare B Match Interrupt: Off
TCCR1A=0x82;
TCCR1B=0x0A;
TCNT1H=0;
TCNT1L=0;
ICR1H=0x00;
ICR1L=0x00;
OCR1A=255;
}