CircuitsFT232H.SPI (circuits_ft232h v0.1.0)

Wires the FT232H's MPSSE engine up as an SPI master.

Pin assignments are fixed for v0.1:

Pin	Role
`ADBUS0`	SCK (output)
`ADBUS1`	MOSI (output)
`ADBUS2`	MISO (input)
`ADBUS3`	CS (active-low, output)

Public API lives on CircuitsFT232H.SPI.Backend (a Circuits.SPI.Backend implementation) and CircuitsFT232H.SPI.Bus (the struct returned by Circuits.SPI.open/2). This module holds the shared MPSSE encoding logic and bus-name conventions used by both.

Summary

Types

config()

Resolved SPI configuration map — matches Circuits.SPI's spi_option_map().

Functions

build_config(opts)

Validates and merges user options against the SPI defaults.

bus_name(id)

Builds the canonical SPI bus name for a device id.

close(id, config)

Tears down an SPI bus: deasserts CS and releases the mode lock so the chip can be reused (e.g. for I2C) without restarting the Device.

configure(id, config)

Configures the FT232H for SPI traffic with the given config. Assumes the chip is already in MPSSE mode and the SPI mode lock has been claimed.

find_descriptor(bus_name)

Looks up the USB.Descriptor whose id matches the SPI bus name.

max_transfer_size()

Maximum number of bytes that can be transferred in one MPSSE call.

parse_bus_name(name)

Parses an SPI bus name into the underlying device id, or returns {:error, :invalid_bus_name}.

transfer(id, config, data)

Runs a full-duplex SPI transfer. Asserts CS, exchanges data for an equal number of MISO bytes, then deasserts CS.

Types

config()

@type config() :: %{
  mode: 0..3,
  bits_per_word: pos_integer(),
  speed_hz: pos_integer(),
  delay_us: non_neg_integer(),
  lsb_first: boolean(),
  sw_lsb_first: boolean()
}

Resolved SPI configuration map — matches Circuits.SPI's spi_option_map().

Functions

build_config(opts)

@spec build_config(keyword()) :: {:ok, config()} | {:error, term()}

Validates and merges user options against the SPI defaults.

bus_name(id)

@spec bus_name(CircuitsFT232H.Device.id()) :: String.t()

Builds the canonical SPI bus name for a device id.

close(id, config)

@spec close(CircuitsFT232H.Device.id(), config()) :: :ok

Tears down an SPI bus: deasserts CS and releases the mode lock so the chip can be reused (e.g. for I2C) without restarting the Device.

configure(id, config)

@spec configure(CircuitsFT232H.Device.id(), config()) :: :ok | {:error, term()}

Configures the FT232H for SPI traffic with the given config. Assumes the chip is already in MPSSE mode and the SPI mode lock has been claimed.

find_descriptor(bus_name)

@spec find_descriptor(String.t()) ::
  {:ok, CircuitsFT232H.USB.Descriptor.t()}
  | {:error, :invalid_bus_name | :not_found | term()}

Looks up the USB.Descriptor whose id matches the SPI bus name.

max_transfer_size()

@spec max_transfer_size() :: pos_integer()

Maximum number of bytes that can be transferred in one MPSSE call.

parse_bus_name(name)

@spec parse_bus_name(String.t()) ::
  {:ok, CircuitsFT232H.Device.id()} | {:error, :invalid_bus_name}

Parses an SPI bus name into the underlying device id, or returns {:error, :invalid_bus_name}.

transfer(id, config, data)

@spec transfer(CircuitsFT232H.Device.id(), config(), binary()) ::
  {:ok, binary()} | {:error, term()}

Runs a full-duplex SPI transfer. Asserts CS, exchanges data for an equal number of MISO bytes, then deasserts CS.