Struct kernel::services::i2c::Transaction

pub struct Transaction {
    addr: Addr,
    tx: KProducer<Transfer>,
    rsp_rx: Reusable<Result<FixedVec<u8>, ErrorKind>>,
    ended: bool,
}

A transaction on the I²C bus.

This type represents a transaction consisting of a series of read and write operations to a target device on an I²C bus with a given Addr. This type is part of a lower-level interface for I²C bus transactions, and is returned by the I2cClient::start_transaction method.

Once a Transaction has been created by I2cClient::start_transaction, data can be written to the target device using the Transaction::write method, and read from the target device using the Transaction::read method. Any number of read and write operations may be performed within a Transaction until an operation with end: true is performed. This completes the transaction.

While a Transaction is in progress, the I²C bus is “locked” by the client that is performing that transaction. Other clients calling I2cClient::start_transaction (or using the embedded_hal_async::i2c::I2c interface) will wait until the current transaction has completed before beginning their own transactions.

Fields

addr: Addr

tx: KProducer<Transfer>

rsp_rx: Reusable<Result<FixedVec<u8>, ErrorKind>>

ended: bool

Implementations

impl Transaction

pub async fn new(__arg0: StartTransaction) -> (Self, KConsumer<Transfer>)

Constructs a new Transaction from the provided StartTransaction message, returning the Transaction and a KConsumer for receiving Transfers within that Transaction.

This is intended to be used by server implementations of the I2cService when handling StartTransaction messages.

pub async fn read( &mut self, buf: FixedVec<u8>, len: usize, end: bool, ) -> Result<FixedVec<u8>, I2cError>

Read len bytes from the I²C bus into buf.

Note that, rather than always filling the entire buffer, this method takes a len argument which specifies the number of bytes to read. This is intended to allow callers to reuse the same FixedVec for multiple read and write operations.

Arguments

• buf: a FixedVec buffer into which bytes read from the I²C bus will be written
• len: the number of bytes to read. This must be less than or equal to buf.len().
• end: whether or not to end the transaction. If this is true, a STOP condition will be sent on the bus once len bytes have been read. If this is false, a repeated START condition will be sent on the bus once len bytes have been read.

Errors

• If an error occurs performing the I²C bus transaction.
• If len is greater than buf.capacity() - buf.len().
• If there is no I2cService running.

Cancelation Safety

If this future is dropped, the underlying I²C bus read operation may still be performed.

pub async fn write( &mut self, buf: FixedVec<u8>, end: bool, ) -> Result<FixedVec<u8>, I2cError>

Write bytes from buf to the I²C.

Arguments

• buf: a FixedVec buffer containing the bytes to write to the I²C bus.
• end: whether or not to end the transaction. If this is true, a STOP condition will be sent on the bus once the entire buffer has been sent. If this is false, a repeated START condition will be sent on the bus once the entire buffer has been written.

Errors

• If an error occurs performing the I²C bus transaction.
• If there is no I2cService running.

Cancelation Safety

If this future is dropped, the underlying I²C bus write operation may still be performed.

async fn xfer( &mut self, buf: FixedVec<u8>, len: usize, end: bool, dir: OpKind, ) -> Result<FixedVec<u8>, I2cError>

impl Transaction

fn buf_too_small(&self, dir: OpKind, len: usize, buf: usize) -> I2cError

fn mk_err(&self, dir: OpKind) -> impl Fn(ErrorKind) -> I2cError

fn mk_no_driver_err<E>(&self, dir: OpKind) -> impl Fn(E) -> I2cError

Trait Implementations

impl Drop for Transaction

fn drop(&mut self)

Executes the destructor for this type.