Struct profirust::phy::LinuxRs485Phy

pub struct LinuxRs485Phy<'a> { /* private fields */ }

Linux userspace PHY implementation for serial TTY devices

Available with the phy-linux feature.

Important: Due to the non-realtime nature of Linux, you must use this PHY implementation with care. You may need to decrease the baudrate or lengthen timeouts (T_SLOT) to get reliable communication. You should also consider running your pogram at “real-time priority” if you need higher bus speeds. It is advisable to run tests with heavy system load to ensure the bus communication stays reliable in all circumstances.

Important 2: If you plan to use this PHY with a USB-serial device, you have to choose your bus parameters even more carefully. Stick to very low baudrates (<= 500kbit/s) and increase T_SL (slot time) to deal with communication delays. Tests have shown a slot time of ~5ms to work reliably (at 500kbit/s, that would be 2500 T_bit). Additionally, it seems to be important to give the OS time to deliver received data by sleeping long enough between poll() calls. A minimum sleep of 2ms was needed in my tests to ensure all received data is delivered in time.

Example

use profirust::{Baudrate, fdl, dp, phy};
const BAUDRATE: Baudrate = Baudrate::B19200;

let mut fdl_master = fdl::FdlMaster::new(
    fdl::ParametersBuilder::new(0x02, BAUDRATE)
        // Increase T_slot (slot time)
        .slot_bits(1920)
        .build_verified(&dp_master)
);

let mut phy = phy::LinuxRs485Phy::new("/dev/ttyS0", fdl_master.parameters().baudrate);

Implementations

impl LinuxRs485Phy<'_>

pub fn new<P: AsRef<Path>>(serial_port: P, baudrate: Baudrate) -> Self

Construct and initialize a new PHY device

This function will attempt to configure the TTY device serial_port for PROFIBUS communication (line settings via termios and RS-485 mode when available).

pub fn wait_transmit(&mut self)

Wait/block until the current transmission completes.

This is useful to save CPU time as the PROFIBUS stack can’t do much anyway until the transmission is over.

Trait Implementations

impl<'a> Debug for LinuxRs485Phy<'a>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<'a> ProfibusPhy for LinuxRs485Phy<'a>

fn poll_transmission(&mut self, _now: Instant) -> bool

Poll an ongoing transmission.

fn transmit_data<F, R>(&mut self, _now: Instant, f: F) -> R

where F: FnOnce(&mut [u8]) -> (usize, R),

Schedule transmission of some data.

fn receive_data<F, R>(&mut self, _now: Instant, f: F) -> R

where F: FnOnce(&[u8]) -> (usize, R),

Try receiving some data.

fn transmit_telegram<F>( &mut self, now: Instant, f: F ) -> Option<TelegramTxResponse>

where F: FnOnce(TelegramTx<'_>) -> Option<TelegramTxResponse>,

Schedule transmission of a telegram.

fn receive_telegram<F, R>(&mut self, now: Instant, f: F) -> Option<R>

where F: FnOnce(Telegram<'_>) -> R,

Try receiving a telegram.

fn poll_pending_received_bytes(&mut self, now: Instant) -> usize

Poll for the current amount of bytes waiting in the receive buffer.