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Check for 3.3V supply before raising IRQ and continuing boot process #72

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Check for 3.3V supply before raising IRQ and continuing boot process #72

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Check for 3.3V supply before raising IRQ and continuing boot process
jannic Jan 27, 2025
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jannic Jan 28, 2025
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106 changes: 82 additions & 24 deletions neotron-bmc-pico/src/main.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -16,10 +16,12 @@ use core::convert::TryFrom;
use heapless::spsc::{Consumer, Producer, Queue};
use rtic::app;
use stm32f0xx_hal::{
gpio::gpioa::{PA10, PA11, PA12, PA15, PA2, PA3, PA4, PA8, PA9},
adc,
adc::Adc,
gpio::gpioa::{PA0, PA10, PA11, PA12, PA15, PA2, PA3, PA4, PA8, PA9},
gpio::gpiob::{PB0, PB3, PB4, PB5},
gpio::gpiof::{PF0, PF1},
gpio::{Alternate, Floating, Input, Output, PullDown, PullUp, PushPull, AF1},
gpio::{Alternate, Analog, Floating, Input, Output, PullDown, PullUp, PushPull, AF1},
pac,
prelude::*,
rcc, serial,
Expand All @@ -41,6 +43,10 @@ const DEBOUNCE_POLL_INTERVAL_MS: u64 = 75;
/// Length of a reset pulse, in milliseconds
const RESET_DURATION_MS: u64 = 250;

/// Minimum voltage level of the 3.3V rail before we start
/// driving the IRQ pin high, to avoid back-powering.
const POWER_GOOD_THRESHOLD_MV: u16 = 3200;

/// The states we can be in controlling the DC power
#[derive(Copy, Clone, PartialEq, Eq)]
#[repr(u8)]
Expand Down Expand Up @@ -170,6 +176,10 @@ mod app {
rcc: Option<rcc::Rcc>,
/// IRQ pin
pin_irq: PA8<Output<PushPull>>,
/// 3.3V monitor pin
pin_3v3_monitor: PA0<Analog>,
/// ADC
adc: Adc,
}

#[monotonic(binds = SysTick, default = true)]
Expand Down Expand Up @@ -204,6 +214,14 @@ mod app {
// Initialize the monotonic timer using the Cortex-M SysTick peripheral
let mono = Systick::new(cp.SYST, rcc.clocks.sysclk().0);

let mut adc = Adc::new(dp.ADC, &mut rcc);
// 8 bit precision should be plenty for our use case
adc.set_precision(adc::AdcPrecision::B_8);
// Approx. sampling time required to charge the 8pF sample & hold
// capacitor through the 10kΩ resistor and to get a reading with 8 bit accuracy:
// 8pF * 10kΩ * ln(2^8) ≈ 440ns ≈ 6 ADC clock cycles
adc.set_sample_time(adc::AdcSampleTime::T_7);

defmt::info!("Creating pins...");
let gpioa = dp.GPIOA.split(&mut rcc);
let gpiob = dp.GPIOB.split(&mut rcc);
Expand Down Expand Up @@ -236,6 +254,8 @@ mod app {
pin_cipo,
pin_copi,
mut pin_irq,
pin_3v3_monitor,
adc,
) = cortex_m::interrupt::free(|cs| {
(
// uart_tx,
Expand Down Expand Up @@ -281,6 +301,10 @@ mod app {
gpioa.pa7.into_alternate_af0(cs),
// pin_irq
gpioa.pa8.into_push_pull_output(cs),
// pin_3v3_monitor
gpioa.pa0.into_analog(cs),
// ADC
adc,
)
});

Expand Down Expand Up @@ -364,6 +388,8 @@ mod app {
press_button_reset_short: debouncr::debounce_2(false),
rcc: Some(rcc),
pin_irq,
pin_3v3_monitor,
adc,
};
let init = init::Monotonics(mono);
(shared_resources, local_resources, init)
Expand All @@ -372,7 +398,7 @@ mod app {
/// Our idle task.
///
/// This task is called when there is nothing else to do.
#[idle(shared = [msg_q_out, msg_q_in, spi, state_dc_power_enabled, pin_dc_on, pin_sys_reset, speaker], local = [pin_irq, rcc, speaker_task_handle: Option<speaker_pwm_stop::MyMono::SpawnHandle> = None])]
#[idle(shared = [msg_q_out, msg_q_in, spi, state_dc_power_enabled, pin_dc_on, pin_sys_reset, speaker], local = [pin_irq, rcc, speaker_task_handle: Option<speaker_pwm_stop::MyMono::SpawnHandle> = None, adc, pin_3v3_monitor])]
fn idle(mut ctx: idle::Context) -> ! {
// TODO: Get this from the VERSION static variable or from PKG_VERSION
let mut register_state = RegisterState {
Expand Down Expand Up @@ -420,7 +446,8 @@ mod app {
}
}
Some(Message::PowerButtonLongPress) => {
if ctx.shared.state_dc_power_enabled.lock(|r| *r) == DcPowerState::On {
let power_state = ctx.shared.state_dc_power_enabled.lock(|r| *r);
if power_state == DcPowerState::On || power_state == DcPowerState::Starting {
defmt::info!("Power off requested!");
ctx.shared
.state_dc_power_enabled
Expand Down Expand Up @@ -452,26 +479,13 @@ mod app {
ctx.shared.pin_sys_reset.lock(|pin| pin.set_low().unwrap());
// Step 4 - Turn on PSU
ctx.shared.pin_dc_on.set_high().unwrap();
// Step 5 - Leave it in reset for a while.
// TODO: Start monitoring 3.3V and 5.0V rails here
// TODO: Take system out of reset when 3.3V and 5.0V are good
// Returns an error if it's already scheduled (but we don't care)
let _ = exit_reset::spawn_after(RESET_DURATION_MS.millis());
// Set 6 - unmask the IRQ
irq_forced_low = false;
// Taking the system out of reset and enabling the IRQ line happens
// later, when the power rail is settled
defmt::info!("Waiting for power-good");
}
}
Some(Message::PowerButtonRelease) => {
if ctx.shared.state_dc_power_enabled.lock(|r| *r) == DcPowerState::Starting {
defmt::info!("Power button released.");
// Button released after power on. Change the power
// state machine t "On". We were in 'Starting' to ignore
// any further button events until the button had been
// released.
ctx.shared
.state_dc_power_enabled
.lock(|r| *r = DcPowerState::On);
}
defmt::info!("Power button released.");
}
Some(Message::ResetButtonShortPress) => {
// Is the board powered on? Don't do a reset if it's powered off.
Expand All @@ -493,7 +507,7 @@ mod app {
}
}
Some(Message::SpiEnable) => {
if ctx.shared.state_dc_power_enabled.lock(|r| *r) != DcPowerState::Off {
if ctx.shared.state_dc_power_enabled.lock(|r| *r) == DcPowerState::On {
// Turn on the SPI peripheral and expect four bytes (the
// length of a Request).
ctx.shared.spi.lock(|s| s.start(4));
Expand Down Expand Up @@ -583,7 +597,51 @@ mod app {
);
}
}
// TODO: Read ADC for 3.3V and 5.0V rails and check good
// TODO: Also monitor 5.0V rail

// Wait for power-good
if ctx.shared.state_dc_power_enabled.lock(|r| *r) == DcPowerState::Starting {
// Reads the absolute voltage of the mon_3v3 line in mV.
// This line is connected to the 3v3 supply through a 50% voltage divider,
// so it should read 1650[mV] nominally.
//
// Note that read_abs_mv is relatively slow, as it internally reads
// ADC values from both the pin and an internal voltage reference, and
// does calculations including integer divisions.
//
// As we do not really require an accurate absolute voltage, but only
// need to be sure that the 3v3 rail is reasonably close to the 3.3VP
// rail (the permanent power rail supplying the BMC), this could be
// rewritten using `ctx.local.adc.read(ctx.local.pin_3v3_monitor)`
// in case performance becomes an issue.
let mon_3v3 = ctx.local.adc.read_abs_mv(ctx.local.pin_3v3_monitor);
defmt::trace!("mon_3v3 reading: {} mV", mon_3v3);
if mon_3v3 < POWER_GOOD_THRESHOLD_MV / 2 {
defmt::info!(
"mon_3v3 below threshold of {} mV: {} mV",
POWER_GOOD_THRESHOLD_MV / 2,
mon_3v3
);
} else {
defmt::info!(
"Power good. Mon_3v3 at {} mV. Continue with startup sequence.",
mon_3v3
);
// Change the power state machine to "On". We were in 'Starting' to ignore
// any further button events until the button had been
// released and to wait for power good.
ctx.shared
.state_dc_power_enabled
.lock(|r| *r = DcPowerState::On);
// Wait a bit before taking system out of reset.
// Returns an error if it's already scheduled (but we don't care)
let _ = exit_reset::spawn_after(RESET_DURATION_MS.millis());
// Unmask the IRQ
irq_forced_low = false;
}
}
// TODO: Shutdown system if mon_3v3 falls below threshold
// TODO: Maybe report voltages to CPU?
}
}

Expand Down Expand Up @@ -797,7 +855,7 @@ mod app {
#[task(shared = [pin_sys_reset, state_dc_power_enabled])]
fn exit_reset(mut ctx: exit_reset::Context) {
defmt::debug!("End reset");
if ctx.shared.state_dc_power_enabled.lock(|r| *r) != DcPowerState::Off {
if ctx.shared.state_dc_power_enabled.lock(|r| *r) == DcPowerState::On {
// Raising the reset line takes the rest of the system out of reset
ctx.shared.pin_sys_reset.lock(|pin| pin.set_high().unwrap());
}
Expand Down
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