 |
C/C++ API Reference
|
Enables data transfer with a specific SPI responder. This class combines a pw::spi::Initiator (representing the physical SPI bus), its configuration data, and a pw::spi::ChipSelector object to uniquely address a device. Transfers to a selected initiator are guarded against concurrent access through the use of the pw::sync::Borrowable object.
pw::spi::Device provides a wrapper for an injected pw::spi::Initiator object, using its methods to configure the bus and perform individual SPI transfers. The injected pw::spi::ChipSelector object is used internally to activate and de-activate the device on-demand from within the data transfer methods.
The Read(), Write(), and WriteRead() methods provide support for performing individual transfers: Read() and Write() perform half-duplex operations, whereas WriteRead() provides support for full-duplex transfers.
The StartTransaction() method provides support for performing multi-part transfers consisting of a series of Read(), Write(), or WriteRead() calls, during which the caller is guaranteed exclusive access to the underlying bus. The Transaction objects returned from this method implements the RAII layer providing exclusive access to the bus; exclusive access locking is released when the pw::spi::Transaction object is destroyed or goes out of scope.
Mutual-exclusion to the pw::spi::Initiator object is provided by the use of the pw::sync::Borrowable object, where the pw::spi::Initiator object is "borrowed" for the duration of a transaction.
Classes | |
| class | Transaction |
Public Member Functions | |
| Device (sync::Borrowable< Initiator > initiator, const Config config, ChipSelector &selector) | |
| Status | Read (ByteSpan read_buffer) |
| Status | Write (ConstByteSpan write_buffer) |
| Status | WriteRead (ConstByteSpan write_buffer, ByteSpan read_buffer) |
| Transaction | StartTransaction (ChipSelectBehavior behavior) |
Synchronously reads data from the SPI responder until the provided read_buffer is full.
This call will configure the bus and activate/deactivate chip select for the transfer.
OkStatus() on success, and implementation-specific values on failure.
|
inline |
Begins a transaction with the SPI device. This creates an RAII Transaction object that ensures that only one entity can access the underlying SPI bus (pw::spi::Initiator) for the object's duration. The behavior parameter provides a means for a client to select how the chip select signal will be applied on Read, Write, or WriteRead calls taking place with the Transaction object. A value of kPerWriteRead will activate/deactivate chip select on each operation, while kPerTransaction will hold the chip select active for the duration of the Transaction object.
|
inline |
Synchronously writes the contents of write_buffer to the SPI responder.
This call will configure the bus and activate/deactivate chip select for the transfer.
OkStatus() on success, and implementation-specific values on failure.
|
inline |
Performs a synchronous read/write transfer with the SPI responder. Data from the write_buffer object is written to the bus, while the read_buffer is populated with incoming data on the bus. In the event the read buffer is smaller than the write buffer (or zero-size), any additional input bytes are discarded. In the event the write buffer is smaller than the read buffer (or zero-size), the output is padded with 0-bits for the remainder of the transfer.
This call will configure the bus and activate/deactivate chip select for the transfer.
OkStatus() on success, and implementation-specific values on failure. 
1.9.6