Implement a simple output voltage regulator

To be improved: inconsistent timing, very slow iteration time.
This commit is contained in:
Thomas Kolb 2023-01-07 23:21:43 +01:00
parent edf697d22b
commit accfc73248

View file

@ -47,6 +47,9 @@ pub static BOOT2: [u8; 256] = rp2040_boot2::BOOT_LOADER_GENERIC_03H;
/// if your board has a different frequency
const XTAL_FREQ_HZ: u32 = 12_000_000u32;
const SWITCH_PWM_MAX: i32 = 512;
const SWITCH_PWM_LIMIT: i32 = 93 * SWITCH_PWM_MAX / 100;
fn convert_adc_measurements(raw: &[u16; 4]) -> (u32, u32, u32)
{
let iout = (raw[0] - raw[1]) as u32 * 3300 * 20 / 4096 / 28; // *20 = division by 50 mΩ shunt
@ -119,14 +122,25 @@ fn main() -> ! {
// Init PWMs
let mut pwm_slices = hal::pwm::Slices::new(pac.PWM, &mut pac.RESETS);
// Configure PWM4
// Configure switch PWM
let pwm5 = &mut pwm_slices.pwm5;
pwm5.set_ph_correct();
pwm5.set_div_int(4);
pwm5.set_div_frac((88 << 4) / 100);
pwm5.set_top(512);
pwm5.set_top(SWITCH_PWM_MAX as u16);
pwm5.enable();
// set up switch PWM output
// note:
// duty cycle = 0 => output voltage = input voltage
// duty cycle = 512 (100%) => input short circuit
//
// general: D = duty cycle (0..1)
// => output voltage = 1/(1-D) * input voltage
let pwr_switch_ch = &mut pwm5.channel_a;
pwr_switch_ch.set_duty(0); // no output by default
pwr_switch_ch.output_to(pins.gpio10);
// LED pins
let mut pin_led_r = pins.gpio13.into_push_pull_output();
let mut pin_led_y = pins.gpio14.into_push_pull_output();
@ -136,11 +150,6 @@ fn main() -> ! {
pin_led_y.set_high().unwrap();
pin_led_g.set_high().unwrap();
// set up switch PWM
let pwr_switch_ch = &mut pwm5.channel_a;
pwr_switch_ch.output_to(pins.gpio10);
pwr_switch_ch.set_duty(400);
// SPI CS pin is controlled by software
let mut spi_cs = pins.gpio5.into_push_pull_output();
spi_cs.set_high().unwrap();
@ -164,7 +173,19 @@ fn main() -> ! {
uart.write_full_blocking(b"Initialization complete!\r\n");
// Infinite loop, fading LED up and down
let vtarget: i32 = 8000;
const GAINSCALE: i32 = 10000;
let pgain: i32 = 50;
let igain: i32 = 100;
let dgain: i32 = 0;
let mut iaccu: i32 = 0;
let mut elast: i32 = 0;
const T: i32 = 1;
// main loop
loop {
let mut adc_value: [u16; 4] = [0; 4];
@ -175,6 +196,39 @@ fn main() -> ! {
let (vin, vout, iout) = convert_adc_measurements(&adc_value);
// PID controller
let err: i32 = -(vout as i32 - vtarget);
iaccu += igain * T * err;
// limit iaccu
if iaccu > SWITCH_PWM_LIMIT * GAINSCALE {
iaccu = SWITCH_PWM_LIMIT * GAINSCALE;
} else if iaccu < 0 {
iaccu = 0;
}
let pval = pgain * err / GAINSCALE;
let ival = iaccu / GAINSCALE;
let dval = dgain * (err - elast) / GAINSCALE;
elast = err;
let ctrlout = pval + ival + dval;
// limit the control value
let pwmval;
if ctrlout > SWITCH_PWM_LIMIT {
pwmval = SWITCH_PWM_LIMIT;
} else if ctrlout < 0 {
pwmval = 0;
} else {
pwmval = ctrlout;
}
pwr_switch_ch.set_duty(pwmval as u16);
{
let mut data: String<16>;
@ -199,7 +253,23 @@ fn main() -> ! {
}
}
uart.write_full_blocking(b"]\r\n");
uart.write_full_blocking(b"]; e=");
data = String::from(err);
uart.write_full_blocking(data.as_bytes());
uart.write_full_blocking(b" => ");
data = String::from(pval);
uart.write_full_blocking(data.as_bytes());
uart.write_full_blocking(b"+");
data = String::from(ival);
uart.write_full_blocking(data.as_bytes());
uart.write_full_blocking(b"+");
data = String::from(dval);
uart.write_full_blocking(data.as_bytes());
uart.write_full_blocking(b" = ");
data = String::from(ctrlout);
uart.write_full_blocking(data.as_bytes());
uart.write_full_blocking(b"\r\n");
}
}
}