Wafer.SPI protocol (wafer v1.1.1)

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A (very simple) protocol for interacting with SPI connected devices.

This API is a minimal version of the Circuits.SPI APIs, except that it takes a Conn which implements SPI as an argument. If you want to use any advanced features, such as bus detection, I advise you to interact with the underlying driver directly.

Deriving

If you're implementing your own Conn type that simply delegates to one of the lower level drivers then you can derive this protocol automatically:

defstruct MySPIDevice do
  @derive Wafer.SPI
  defstruct [:conn]
end

If your type uses a key other than conn for the inner connection you can specify it while deriving:

defstruct MySPIDevice do
  @derive {Wafer.SPI, key: :spi_conn}
  defstruct [:spi_conn]
end

Summary

Types

data()
t()

All the types that implement this protocol.

Functions

transfer(conn, data)

Perform an SPI transfer.

Types

data()

@type data() :: binary()

t()

@type t() :: term()

All the types that implement this protocol.

Functions

transfer(conn, data)

@spec transfer(Wafer.Conn.t(), data()) ::
  {:ok, data(), Wafer.Conn.t()} | {:error, reason :: any()}

Perform an SPI transfer.

SPI transfers are synchronous, so data should be a binary of bytes to send to the device, and you will receive back a binary of the same length containing the data received from the device.