Enum esp_idf_svc::hal::can::config::Filter

pub enum Filter {
    Standard {
        filter: u16,
        mask: u16,
    },
    Dual {
        filter1: u16,
        mask1: u16,
        filter2: u16,
        mask2: u16,
    },
    Extended {
        filter: u32,
        mask: u32,
    },
}

Is used to filter out unwanted CAN IDs (messages).

Notice that Espressif TWAI (CAN in rest of the world) acceptance filtering works differently than common CAN filtering (for example mask bits are inversed). However here those differences are hidden away from the user and common CAN filtering is used.

mask is used to determine which bits in the incoming CAN ID are compared with the filter value. Bits in mask mean: 0: do not care - the bit is not used for the comparison 1: must match - the bit of the incoming CAN ID must have the same state as in filter

Notice that if mask is 0, all CAN IDs are accepted regardless of filter value.

Examples

This shows how 11 bit CAN ID 0x3AA goes through filtering engine and is finally accepted:

// incoming id [ 0 1 1 1 0 1 0 1 0 1 0 ]
// mask        [ 1 0 1 0 0 1 1 1 0 0 0 ]
//               1 = compare
//               0 = do not care
// masked id   [ 0 _ 1 _ _ 1 0 1 _ _ _ ]
// filter      [ 0 0 1 1 1 1 0 1 0 1 1 ]

// incoming id [ 0 1 1 1 0 1 0 1 0 1 0 ]
// accepted

Notice that for example 0x7AA would not be accepted because its MSB bit is 1, but filter only accepts 0 in this bit position and mask says that this bit must be compared.

Accept only CAN ID 0x567

let filter = 0x567;
// every bit must match filter
let mask   = 0x7FF;
let f = Filter::Standard { filter, mask };

Accept CAN IDs 0x560 - 0x56F

let filter = 0x560;
// do not care about 4 LSB bits
let mask   = 0x7F0;
let f = Filter::Standard { filter, mask };

Variants

Standard

Fields

filter: u16

mask: u16

Filter for 11 bit standard CAN IDs

Dual

Fields

filter1: u16

mask1: u16

filter2: u16

mask2: u16

Filter for two 11 bit standard CAN IDs

Extended

Fields

filter: u32

mask: u32

Filter for 29 bit extended CAN IDs

Implementations

impl Filter

pub fn standard_allow_all() -> Filter

Filter that allows all standard CAN IDs.

pub fn extended_allow_all() -> Filter

Filter that accepts all extended CAN IDs.

Trait Implementations

impl Clone for Filter

fn clone(&self) -> Filter

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Filter

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

Formats the value using the given formatter.

impl Default for Filter

fn default() -> Filter

Returns the “default value” for a type.

impl PartialEq for Filter

fn eq(&self, other: &Filter) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Copy for Filter

impl Eq for Filter

impl StructuralPartialEq for Filter