FTDI Synchronous Serial

A lean stack written primarily in Swift for using the FTDI FT232H USB-to-serial adapter in I2C, SPI, and GPIO applications, built on the portable C-library libusb.

Overview

This library provides

• support for a USB-connected FTDI device in MPSSE mode
• implementations of I2C and SPI protocols
• uses deft-simple-usb for usermode access to the FTDI device

Synchronous serial communication is data that is timed according to a separate clock signal. While the FTDI also supports asynchronous [UART] communications (such as RS-232), the operating system likely provides support for this mode through one of the /dev/cuserial special devices.

Requirements

• Swift Package Manager
• Swift 5.3+
• macOS or Linux
• for FTDI serial devices: an FT232H connected via USB

Mac requirements

• macOS 10.15 (Catalina) or higher

SPM Dependencies

• swift-log

Linux dependencies

• libusb

Goals

• make installation and use as easy as possible
• minimize additions to the user's environment
• use usermode drivers
• avoid components that require root access to install or configure
• use Swift as much as possible
• aspire to code that is readable and idiomatic

Usage

Logging

Loggers are instantiated using the deft-log library using the label prefix com.didactek.ftdi-synchronous-serial.

Installation Notes

Linux device permissions

On Linux, users will not have access to a hot-plugged FTDI device by default. The cleanest way to systematically grant permissions to the device is to set up a udev rule that adjusts permissions whenever the device is connected.

The paths and group in the template below assume:

• Configuration files are under /etc/udev/rules.d
• The group 'plugdev' exists and includes the user wanting to use the device

Under /etc/udev/rules.d/, create a file (suggested name: "70-gpio-ftdi-ft232h.rules") with the contents:

# FTDI FT232H USB -> GPIO + serial adapter
# 2020-09-07 support working with the FT232H using Swift ftdi-synchronous-serial library
ACTION=="add", SUBSYSTEM=="usb", ATTRS{idVendor}=="0403", ATTRS{idProduct}=="6014", MODE="660", GROUP="plugdev"

eLinux.org has a useful wiki entry on accessing devices without sudo.