CircuitsFT232H.GPIO (circuits_ft232h v0.1.0)

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GPIO support for the FT232H's general-purpose pins.

The FT232H exposes 16 GPIO pins. The labels match the silkscreen on the Adafruit FT232H breakout:

LabelLinear pin numberNotes
AD00Shared with SCK (SPI) / SCL (I2C)
AD11Shared with MOSI / SDA-out
AD22Shared with MISO / SDA-in
AD33Shared with CS (SPI)
AD4-AD74..7Free
AC0-AC78..15Free

GPIO can run alongside an active I2C or SPI bus on the same chip, provided the pin doesn't overlap with the protocol's reserved pins (see the table above). The CircuitsFT232H.Device GenServer enforces this.

Public API lives on CircuitsFT232H.GPIO.Backend (a Circuits.GPIO.Backend implementation) and CircuitsFT232H.GPIO.Handle (the per-pin handle returned by Circuits.GPIO.open/3). This module holds shared parsing and identifier helpers.

Summary

Types

pin()
pin_ref()

Combined identifier for one FT232H pin: device id + pin number + label.

Functions

all_pin_refs()

Lists all GPIO pins on every connected FT232H, in canonical order.

find_descriptor(controller)

Looks up the USB.Descriptor for the given controller id, or an error if no chip with that id is connected.

identifiers(map)

Builds a Circuits.GPIO.identifiers() map for pin_ref.

label(pin)

Returns the label for a linear pin number (0..15).

parse_label(label)

Parses an "AD<n>"/"AC<n>" label into a linear pin number.

resolve(label_or_offset)

Resolves a Circuits.GPIO.gpio_spec() into a fully qualified pin_ref identifying both the chip and the pin within it.

Types

pin()

@type pin() :: CircuitsFT232H.Device.pin()

pin_ref()

@type pin_ref() :: %{
  controller: CircuitsFT232H.Device.id(),
  pin: pin(),
  label: String.t()
}

Combined identifier for one FT232H pin: device id + pin number + label.

Functions

all_pin_refs()

@spec all_pin_refs() :: [pin_ref()]

Lists all GPIO pins on every connected FT232H, in canonical order.

find_descriptor(controller)

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

Looks up the USB.Descriptor for the given controller id, or an error if no chip with that id is connected.

identifiers(map)

@spec identifiers(pin_ref()) :: map()

Builds a Circuits.GPIO.identifiers() map for pin_ref.

label(pin)

@spec label(pin()) :: String.t()

Returns the label for a linear pin number (0..15).

parse_label(label)

@spec parse_label(String.t()) :: {:ok, pin()} | {:error, :invalid_label}

Parses an "AD<n>"/"AC<n>" label into a linear pin number.

resolve(label_or_offset)

@spec resolve(any()) ::
  {:ok, pin_ref()}
  | {:error,
     :invalid_label | :invalid_pin | :no_device | :ambiguous_device | term()}

Resolves a Circuits.GPIO.gpio_spec() into a fully qualified pin_ref identifying both the chip and the pin within it.

Accepted forms:

  • {controller, line_offset} — e.g. {"ftdi-3:8", 4}
  • {controller, label} — e.g. {"ftdi-3:8", "AD4"}
  • label — e.g. "AD4"; requires exactly one FT232H attached
  • line_offset (integer 0..15) — requires exactly one FT232H attached