Struct stm32_eth::ptp::EthernetPTP

pub struct EthernetPTP { /* private fields */ }

Access to the IEEE 1508v2 PTP peripheral present on the ethernet peripheral.

On STM32FXXX’s, the PTP peripheral has/uses the following important parts:

• HCLK (the chip’s high speed clock, configured externally).
• The global timestamp (global_time, a Timestamp).
• A subsecond increment register (subsecond_increment, a Subseconds with a value of 0 to 255, see EthernetPTP::subsecond_increment).
• An accumulator register (accumulator, an u32).
• An addend register (addend, an u32, see EthernetPTP::addend and EthernetPTP::set_addend).

To ensure that global_time advances at the correct rate, the system performs the following steps:

1. On every clock of HCLK, addend is added to accumulator.
2. If accumulator overflows during step 1, add subsecond_increment to global_time.

When a new EthernetPTP is created, it is assumed that the frequency of HCLK is exactly correct. Using HCLK, values for subsecond_increment and addend are calculated so that global_time represents real-time.

Subsequently, addend can be adjusted to compensate for possible errors in HCLK, using EthernetPTP::addend and EthernetPTP::set_addend

To assess the correctness of the current speed at which global_time is running, one can use the following equation:

clock_ratio = ((2^31 / subsecond_increment) / (HCLK_HZ * (addend / 2^32)))

Values greater than 1 indicate that the provided HCLK_HZ is less than the actual frequency of HCLK, which should be compensated by increasing addend. Values less than 1 indicate that the provided HCLK_HZ is greater than the actual frequency of HCLK, which should be compensated by decreasing addend.

Implementations

impl EthernetPTP

pub fn subsecond_increment(&self) -> Subseconds

Get the configured subsecond increment.

pub fn addend(&self) -> u32

Get the currently configured PTP clock addend.

pub fn set_addend(&mut self, rate: u32)

Set the PTP clock addend.

pub fn set_time(&mut self, time: Timestamp)

Set the current time.

pub fn update_time(&mut self, time: Timestamp)

Add the provided time to the current time, atomically.

If time is negative, it will instead be subtracted from the system time.

pub fn get_time(&self) -> Timestamp

Get the current time.

pub fn enable_pps<P>(&mut self, pin: P) -> P::Outputwhere
    P: PPSPin,

Enable the PPS output on the provided pin.

impl EthernetPTP

Setting and configuring target time interrupts on the STM32F107 does not make any sense: we can generate the interrupt, but it is impossible to clear the flag as the register required to do so does not exist.

pub fn configure_target_time_interrupt(&mut self, timestamp: Timestamp)

Configure the target time interrupt.

You must call EthernetPTP::interrupt_handler in the ETH interrupt to detect (and clear) the correct status bits.

pub fn interrupt_handler(&mut self) -> bool

Returns a boolean indicating whether or not the interrupt was caused by a Timestamp trigger and clears the interrupt flag.

pub fn set_pps_freq(&mut self, pps_freq: u8)

Configure the PPS output frequency.

The PPS output frequency becomes 2 ^ pps_freq. pps_freq is clamped to [0..31].