Struct BusTiming 

pub struct BusTiming { /* private fields */ }

Tracks bus activity and enforces minimum frame spacing.

Thread-safe: uses AtomicU64 for lock-free timestamp updates. Pass to crate::ClientOptions::with_bus_timing to activate.

Frame spacing

1. Every bus I/O event (read/write) calls touch to record the last activity timestamp.
2. Before sending, wait_if_needed checks if enough time has elapsed. If not, it sleeps for the remaining gap.

Examples

use std::time::Duration;
use oms_modbus::BusTiming;

// RTU 3.5T @ 9600 baud ≈ 4.01ms
let timing = BusTiming::rtu_35t(9600);

// Custom 100ms — for slow devices
let timing = BusTiming::custom(Duration::from_millis(100));

Implementations

impl BusTiming

pub fn custom(min_spacing: Duration) -> Self

Create with a custom minimum spacing.

use std::time::Duration;
use oms_modbus::BusTiming;
let timing = BusTiming::custom(Duration::from_millis(50));

pub fn rtu_35t(baud_rate: u32) -> Self

RTU standard 3.5 character times at the given baud rate.

Per MODBUS over Serial Line Specification V1.02 §1.4:

• ≤ 19200 bps: 3.5 × 11 bits / baud_rate (the full formula).
• > 19200 bps: fixed minimum of 1.75 ms (1750 µs).

Without the cap, 115200 baud would give only ~334 µs — too short for real RS-485 transceivers and low-end MCU interrupt latency. Use rtu_35t_raw if you need the uncapped formula.

Baud	3.5T spacing
9600	~4.01 ms
19200	~2.01 ms
38400	1.75 ms
115200	1.75 ms
921600	1.75 ms

pub fn rtu_35t_raw(baud_rate: u32) -> Self

Raw 3.5 character-time formula at any baud rate — no 1.75 ms cap.

Unlike rtu_35t, this always computes the raw formula, even at high baud rates where the Modbus spec recommends a fixed minimum of 1.75 ms. Baud rate 0 is silently clamped to 1. Use this only if you understand the implications for your specific hardware.

use oms_modbus::BusTiming;
// 115200 baud → ~334 µs (raw formula, no cap)
let timing = BusTiming::rtu_35t_raw(115200);
assert_eq!(timing.min_spacing().as_micros(), 334);

pub fn ascii_35t(baud_rate: u32) -> Self

ASCII standard 3.5 character times — same timing as RTU.

pub fn touch(&self)

Record bus activity at the current instant.

Call on every I/O read/write to keep the timestamp fresh. Uses a monotonic, syscall-free clock for microsecond timestamps.

pub async fn wait_if_needed(&self)

Wait until the minimum spacing has elapsed since the last touch.

Returns immediately (no sleep) if:

• Enough time has already passed
• No previous activity was recorded (first call)

pub fn min_spacing(&self) -> Duration

Current minimum spacing.

Trait Implementations

impl Debug for BusTiming

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

Formats the value using the given formatter.