madcow/drybox-core
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Try setting variable PWM frequency with timer2

Browse Source
This commit is contained in:
Leon Krieg
2024-09-04 15:57:38 +02:00
parent ad987996e0
commit 992899f0cb
3 changed files with 22 additions and 10 deletions
Download Patch File Download Diff File Expand all files Collapse all files

23
src/bus/pwm.c
View File

@@ -7,19 +7,30 @@ int PWM_Init(void)
// PD5: PWM NF-A8 Fan Peltier Cold Side
// PD7: PWM NF-R8 Fan Heating Element
DDRD |= BIT(PD4) | BIT(PD5) | BIT(PD7);
DDRD |= BIT(PD4) | BIT(PD5); // | BIT(PD7);
// Fast mode, non-inverting, no prescaling
// Timer1: Fast mode, non-inverting, top=ICR1, prescale /1
TCCR1A = BIT(WGM11) | BIT(COM1A1) | BIT(COM1B1);
TCCR1B = BIT(WGM12) | BIT(WGM13) | BIT(CS10);
TCCR2 = BIT(WGM20) | BIT(WGM21) | BIT(COM21) | BIT(CS20);
ICR1 = PWM_CYCLE_TOP; // 8000 MHz / 25000 KHz
// TODO: Enable 25 KHz frequency for timer 3
OCR1A = FAN01_MIN_DUTY;
OCR1B = FAN02_MIN_DUTY;
OCR2 = FAN03_MIN_DUTY;
// ATMega32A does not have more than two outputs for the
// 16-bit timer and the other 8-bit timers don't have modes
// where the value of TOP can be changed. We can only get
// 25 KHz with software PWM on this chip as far as I know.
// The 328P would allow us to use OCR2A as top but with
// 8-bit this gives us a really low duty step size of 2.5%.
// Timer2: Fast mode, non-inverting, top=0xFF, prescale /8
// Top set to 8000000 (f_cpu) / 8 (prescale) / 25000 (f_pwm) - 1
// TCCR2 = BIT(WGM20) | BIT(WGM21) | BIT(COM21) | BIT(CS21);
// OCR2 = 40 - 1; // XXX: OCR2A=top OCR2B=duty
TCCR2 = 0;
OCR2 = 0;
return 0;
}

3
src/bus/pwm.h
View File

@@ -8,7 +8,8 @@
#define FAN02 PD5 // NF-A8 Fan Peltier Cold Side Speed
#define FAN03 PD7 // NF-R8 Fan Heating Element Speed
#define PWM_CYCLE_TOP (F_CPU / 25000) // 25 KHz
#define PWM_CYCLE_TOP (F_CPU / 25000 - 1) // 8 MHz / 25 KHz
#define FAN01_MIN_DUTY (PWM_CYCLE_TOP * 0.2f)
#define FAN02_MIN_DUTY (PWM_CYCLE_TOP * 0.2f)
#define FAN03_MIN_DUTY (PWM_CYCLE_TOP * 0.2f)

6
src/main.c
View File

@@ -54,9 +54,9 @@ int Init(void)
// complicated so it might be worth it to switch to
// something like an ATmega328PB.
PWM_SetValue(FAN01, 50);
PWM_SetValue(FAN02, 50);
PWM_SetValue(FAN03, 20);
PWM_SetValue(FAN01, 50); // Fan Peltier Hot side
PWM_SetValue(FAN02, 50); // Fan Peltier Cold Side
// PWM_SetValue(FAN03, 20); // Fan Heating
// The I2C_SetChannel command changes the channel
// setting of the PCA9546 I2C multiplexer. Any