PyFtdi

Overview

PyFtdi aims at providing a user-space driver for modern FTDI devices, implemented in pure Python language.

Modern FTDI devices include:

• FT232R (single port, clock up to 6 MHz, 3Mbps)
• FT2232D (dual port, clock up to 6 MHz)
• FT232H (single port, clock up to 30 MHz)
• FT2232H (dual port, clock up to 30 MHz)
• FT4232H (quad port, clock up to 30 MHz)
• FT230X (single port, clock up to 48 Mhz, 3Mbps)

Other FTDI devices could also be supported (including FT232* devices), although these devices are not a primary goal for PyFtdi, and therefore have not been tested with PyFtdi.

Primary goals

It should support the following modes:

• UART/Serial USB converter, up to 12Mbps (depending on the FTDI device capability)
• SPI master
• JTAG master
• Bitbang/GPIO support (not a primary goal)

PyFtdi should provide a pyserial compliant API, to be used as a drop-in module to access USB-serial converters based on FTDI devices.

Requirements

PyFtdi relies on PyUSB, which itself depends on one of the following native libraries:

• libusb-1.0 (recommended), tested with 1.0.18
• libusbx-1.0, tested with 1.0.17
• libusb-0.1 (deprecated), tested with 0.1.4
• openusb (not tested with pyftdi)

PyFtdi does not depend on any other native library, and only uses standard Python modules.

PyFTDI has been tested with PyUSB 1.0.0b1 and PyUSB 1.0.0b2. PyFTDI deals with the API break introduced with PyUSB 1.0.0b2.

To use the serial port feature of PyFtdi, pyserial 2.6+ module should be installed. Previous versions of pyserial will NOT work.

Python 2.6 or above is required. Python 3.x is not yet supported.

Status

This project is still in beta development stage.

However, PyFtdi is being forked from a closed-source software implementation that has been successfully used for over a year - including serial, spi and jtag protocols, based on top of the libftdi open source library.

libftdi is now being phased out from this closed-source project and replaced with PyFtdi, to ease maintenance and customization.

Meanwhile, PyFtdi is developed as an open-source solution.

Supported features

• All FTDI device ports (UART, MPSSE) can be used simultaneously.
• Serial port, up to 12 Mbps. PyFtdi includes a pyserial emulation layer that offers transparent access to the FTDI serial ports through a pyserial-compliant API. The serialext directory contains a minimal serial terminal demonstrating the use of this extension, and a dispatcher automatically selecting the serial backend (pyserial, PyFtdi), based on the serial port name.
• SPI master. For now, SPI Mode 0 (CPOL=0, CPHA=0) is the only supported mode. It should be easy to extend the SPI master to deal with less common modes. PyFtdi can be used with pyspiflash module that demonstrates how to use the FTDI SPI master with a pure-Python serial flash device driver for several common devices.
• JTAG is under development and is not fully supported yet.

Installation

• Download & install pyusb-1.0.0b1: pip install [--pre] pyusb==1.0.0b2
  • --pre tag is required with latest release of pip, as pyusb is still in beta status
• Download & install pyserial: pip install pyserial
• Install pyftdi

Troubleshooting

"Error: No backend available"

libusb native library cannot be loaded. Try helping the dynamic loader:

• On Linux: export LD_LIBRARY_PATH=<path>

  where <path> is the directory containing the libusb-1.*.so library file

• On OS X: export DYLD_LIBRARY_PATH=.../lib

  where <path> is the directory containing the libusb-1.*.dylib library file

"Error: Access denied (insufficient permissions)"

The system may already be using the device.

• On OS X 10.9+: starting with Mavericks, OS X ships with a native FTDI driver that preempts access to the FTDI device.

  The driver can be unloaded this way:

  sudo kextunload [-v] -bundle com.apple.driver.AppleUSBFTDI

  Please note that the system automatically reloads the driver, so it may be useful to move the kernel extension so that the system never loads it.

"serial.serialutil.SerialException: Unable to open USB port"

May be caused by a conflict with the FTDI virtual COM port (VCOM). Try uninstalling the driver. On OS X, refer to this FTDI guide:

Development

PyFtdi is developed on Mac OS X platforms (including 64-bit kernels), and is validated on a regular basis on Linux hosts.

As it contains no native code, it should work on any PyUSB and libusb supported platforms. However, Ms Windows is a seamless source of issues and is not supported. Your mileage may vary.

Examples

See pyftdi/examples directory for JTAG examples. See pyspiflash module for SPI examples.