NOTE

Check new ftdi-embedded-hal project in the ftdi-rs organization for the up-to-date implementation of FTDI MPSSE embedded HAL.

ftdi-embedded-hal

Implementation of the embedded-hal traits for FTDI chips supporting Multi Protocol Synchronous Serial Engine (MPSSE).

This implementation of embedded-hal allows you to work with various SPI/I2C devices over USB. If your Linux board has accessible I2C or SPI pins, then it is possible to connect I2C/SPI devices directly. For this purpose linux-embedded-hal implementation of embedded-hal traits can be used. However normal Linux workstations usually do not have direct access to SPI/I2C, but have enough USB ports. In this case ftdi-embedded-hal can be used. For instance, this may come particularly handy for playing with various I2C/SPI devices, e.g. trying them out or working on driver development.

Devices

Currently support for GPIO/SPI/I2C on FT232H and FT2232H chips has been implemented. There are many development boards and modules for FTDI chips. The following modules have been used for development and testing:

• FT232H development module UM232H
• FT232H development module CJMCU-232H
• FT2232H development module

Features, limitations, TODO

Brief list of features supported out of the box:

• supported devices: FT232H, FT2232H
• MPSSE mode is supported, no pure bit-banging support
• SPI/I2C/GPIO support
  • SPI
    • MODE0, MODE2
    • 500kHz, 1MHz, 3MHz, 5MHz
  • I2C bus
    • 100kHz, 400kHz
  • GPIO
    • output mode only

Limitations:

• FTDI device is selected by USB PID/VID, so only the first connected device will be handled
• no gpio input support
• i2c/spi are mutually exclusive due to h/w circuitry (not sure if anything can be done from s/w side to support both simultaneously)
• GPIO functionality is disabled for ADBUS[0..3] and BDBUS[0..4] pins (SK/DI/DO/CS)
• no support for SPI MODE1 and MODE3 (not sure if anything can be done from s/w side as this is a limitation for FTDI chips)
• not enough flexibility in clock selection
  • fixed list of suppported SPI/I2C frequencies
  • clock is selected once for the first bus instance and should be the same for all the other bus instances, runtime changes are not supported
• tests can be run only when FTDI devices are connected

TODO:

• [ ] more cleanup and refactoring in terms of idiomatic Rust
• [ ] suppport several connected FTDI devices with the same USB PID/VID
• [ ] enable ADBUS[0..3] and BDBUS[0..3] pins as GPIO pins as well, just keep track of selected functionality, it is already done anyway to disable i2c and spi at the same time
• [ ] add gpio input support
• [ ] add support for FT4232H
• [ ] more flexibility in clock configuration (?)
• [ ] add more I2C/SPI/GPIO examples/tests, e.g. 74HC595, MCP3008, PCF8574, and more

Circuit examples

SPI nRF24L01+ breakout board

I2C EEPROM at24c04

Useful documents and links

Projects

• ftdi - Rust wrapper over libftdi1 library for FTDI devices
• embedded-hal - Hardware Abstraction Layer (HAL) for embedded systems
• linux-embedded-hal - implementation of the embedded-hal traits for Linux devices
• device driver crates that use embedded-hal interface

Data sheets for FTDI chips and development modules:

• FT232H datasheet
• FT2232H datasheet
• UM232H module datasheet

Application notes provided by FTDI:

• AN 135: FTDI MPSSE Basics
• AN 108: Command Processor for MPSSE and MCU Host Bus Emulation Modes
• AN 113: Interfacing FT2232H Hi-Speed Devices to I2C Bus
• AN 114: Interfacing FT2232H Hi-Speed Devices to SPI Bus
• Interfacing FTDI USB Hi-Speed Devices to a JTAG TAP