Libmpsse is a library for interfacing with SPI/I2C devices via FTDI's FT-2232 family of USB to serial chips. Additionally, it provides control over the GPIO pins on the FTDI chips and supports a raw bitbang mode as well. Based around the libftdi library, it is written in C and includes a Python wrapper courtesy of swig.
In version 1.0 libmpsse was modified to support multiple simultaneous FTDI chips inside a single process, which required a change to the API. Thus, the API for libmpsse versions prior to 1.0 are not compatible with the API for versions 1.0 and later.
The C and Python APIs are very similar, although the Python API has been made more "pythonic". Specifically, in Python:
MPSSE is the name of the Python class, not of a method or function as it is in C. The class constructor takes the same arguments as the MPSSE function in C. If you wish to instead use the Open method to open a given device, simply do not specify these arguments when calling the class constructor.
Due to its object-oriented nature, each class instance in Python internally handles the MPSSE context pointer; thus, none of the Python methods in the MPSSE class require this argument.
Size parameters required by the C functions are not used by the corresponding Python methods.
Besides the above described differences, all Python methods have a 1:1 compatibility with their respective C functions. However, in Python the class constructor (MPSSE) and Open method have sensible defaults for several of their arguments so not all arguments are required.
There are SPI and I2C code examples for both C and Python in the
src/examples directory. After installing
libmpsse, the C examples can be built by running:
$ make example-code
To build applications in Python, you must import the
from mpsse import *
To build applications in C, you must include the
mpsse.h header file:
...and also link your program against the libmpsse library:
$ gcc test.c -o test -lmpsse
In order to speak to SPI or I2C devices, you must establish the proper physical connections between the target device and your FTDI chip. The exact pin out of your target device and FTDI chip will differ based on the chips in question, and the appropriate data sheets for each device should be referenced for this information.
Included in the docs directory is the FTDI MPSSE Basics application note (AN 135). Section 2 of this document covers all of the pin configurations for each FTDI chip, as well as example diagrams regarding the physical connections between the FTDI chip and your target device.
The following are known bugs in libmpsse:
- In SPI, the Transfer method fails if transfering large data chunks. Use the Read/Write functions for transferring large chunks of data (~1MB or more).
Libmpsse supports all four SPI modes as well as I2C. However, due to the design of the FTDI MPSSE implementation, there are some limitations:
- All protocols support master mode only.
- SPI modes 1 and 3 are only partially supported; see the README.SPI for more information.
- In I2C, the SCL and SDA pins are open drain, but the MPSSE implementation explicitly drives these lines high. Although this is usually fine, it means that some I2C features, such as clock stretching, are not supported.