This python module and interface connectors allow python to be used to communicate with a BT82x device using FT4232H, FT232H or FT4222H devices.
The FT4232H and FT232H methods use the MPSSE Interface of the devices to communicate over SPI to the BT82x. The FT4222H Interface has built-in SPI hardware and controller.
For MPSSE devices the pyftdi module for python and the libMPSSE-SPI library are required.
The connector code supports the UMFTPD2A(see note 1) module from Bridgetek, USB to MPSSE cables such as the VA800-SPI or C232HM.
The connector ft4232h supports the quad-channel FT4232H devices and the connector ft232h supports the single-channel FT232H devices.
Note 1: A pin header and jumper cables are required to interface the CN2 connector to the BT82x development board.
All platforms will require a working up-to-date installation of python 3.13.x or later. These instructions assume the use of pip to install required pyftdi package.
pip install pyftdi
This code may also be used with circuitpython, however this is not yet supported.
To connunicate with the MPSSE interface on Windows the standard FTDI drivers cannot be used. These must be replaced with a libusb driver in order for pyftdi to access the device directly. It is not necessary to replace the drivers for all the interfaces on the FTDI devices, just the one used for MPSSE.
The Zadig utility is a handy utility that will replace a driver with libusb. Click on the menu item "Options", then "List all Devices". For a UMFTPD2A board,from the drop-down box select UMFTPD2A (Interface 1) and for the driver choose libusb-win32, then click "Replace Driver".
It may be neccessary to reboot the PC or remove and replug the MPSSE device. Once this is done the interface for the device will show in Windows Device Manager. Note that there is a missing USB Serial Port (COM4) now.
These instructions are incomplete! The built-in Linux drivers for FTDI devices need to be disabled for the libusb driver to be invoked.
MPSSE Bus numbers refer to the MPSSE interface signals.
The header on the BT82x board has the following connections:
| Pin | Name | Description |
|---|---|---|
| 1 | SCK | SPI SCK - Clock |
| 2 | CS# | SPI CS# Serial Chip Select signal, active LOW |
| 3 | MOSI | SPI MOSI - Master Out Slave In |
| 4 | MISO | SPI MISO - Master In Slave Out |
| 5 | INT# | Interrupt signal from BT82x, active LOW |
| 6 | RESET# | Powerdown signal from SPI host, active LOW |
| 7 | NC | no connection |
| 8 | NC | no connection |
| 9 | GND | Signal GND for SPI |
| 10 | GND | Signal GND for SPI |
For an MPSSE cable use the MPSSE SPI connections as per Application Note AN_188.
The following cable coloured wires are connected to the BT82x development board:
| Bus | Cable | Name |
|---|---|---|
| MPSSE0 | SK (Orange) | SPI SCK - Clock |
| MPSSE1 | DO (Yellow) | SPI MOSI - Master Out Slave In |
| MPSSE2 | DI (Green) | SPI MISO - Master In Slave Out |
| MPSSE3 | CS (Brown) | SPI CS# - Serial Chip Select signal |
| MPSSE7 | GPIO L3 (Blue) | PD# - Powerdown signal |
| N/A | GND (Black) | Signal GND for SPI |
On UMFTPD2A the CN2 connector is a 12-pin 2.54 mm pitch through hole connector. It is recommended that a through hole pin header is soldered into the connector and short male-to-male jumper cables used to connect to the BT82x board. The CN2 pins are connected as follows:
| Bus | Pin | Name |
|---|---|---|
| MPSSE0 | CN2-1 | SCLK - Clock |
| MPSSE3 | CN2-2 | CS - Serial Chip Select signal |
| MPSSE1 | CN2-3 | MOSI - Master Out Slave In |
| MPSSE2 | CN2-4 | MISO - Master In Slave Out |
| MPSSE7 | CN2-10 | PD# - Powerdown signal |
| N/A | CN2-7 | Signal GND for SPI |
The FT4222 device is supported using the python-ft4222 module for python and the libFT4222 library from FTDI.
The connector ft4222module supports for FT4222H devices from FTDI.
All platforms will require a working up-to-date installation of python 3.13.x or later. These instructions assume the use of pip to install required python-ft4222 package.
pip install ft4222
This code may also be used with circuitpython, however this is not yet supported.
| File/Folder | Description |
|---|---|
| bteve2 | Module and library code for BT82x |
| connectors | Code to interface between library code and hardware |
| docs | Documentation and images for documentation |
| common | Common files shared between demos |
| apprunner.py | Wrapper code to setup library, connector and application |
| simple.py | Simple example code |
| fontmagic.py | Simple example code demonstrating scaling and rotating fonts |
| segment.py | Simple seven segment demo code |
| b2tf.py | Advanced seven segment demo code |
This is a wrapper program the selects the command line parameters and chooses a connector. It establishes a module for the BT82x API library and then calls the example program with the graphics descriptor (gd) and EVE definitions (eve) setup.
This makes a module for the BT82x interface allowing calls from python to be encoded as binary commands for the BT82x.
To run the python code and connect to a BT82x a connector is required. The connector is selected in the parameters to the example programs. It opens a port to the device that makes the SPI signals and sets-up the target device. API interfaces for reset, wr, rd, cs functions are required.
There are supported connectors for FT4232H (ft4232h.py), FT232H (ft232h.py), FT4222H (ft4222module.py). The FT4232H connector uses the first MPSSE interface, if it fails to open that then the second MPSSE interface (USB Interface 1) is used. The the CN2 connector on the UMFTPD2A board is connected to the second MPSSE interface.
Connectors to other transports are simple to make. The reset function must be able to setup the BT82x in line with the provided code in supported connectors. The use of Chip Select in the cs function is required rather than automatic action of chip select on some devices.
The apprunner wrapper looks for the --connector parameter and attempts to find a connector python file in the connectors directory with a matching name. All other parameters are passed to the example code.
In the example code the apprunner and bteve2 libraries are imported. A function is made which takes a parameter called gd (graphics descriptor) which is used to access the BT82x. At the top level of python script a call is made to apprunner with the name of the function. This sets up the environment for drawing on the BT82x.
The simplest example code will therefore be:
import apprunner
import bteve2 as eve
def simple(gd):
# Start drawing test screen.
gd.begin()
gd.ClearColorRGB(64,72,64)
gd.Clear(1,1,1)
gd.Display()
gd.swap()
apprunner.run(simple)
This simple program demonstrates writing text on the screen, it parses arguments and uses them to determine the display list for the BT82x.
The format of the command is as follows:
MPSSE example
python simple.py --connector ft232h "simple program to write to the screen" --font 25
FT4222 example
python simple.py --connector ft4222module "simple program to write to the screen" --font 25
The string in quotes is used in a CMD_TEXT call with the font number set in the --font parameter. Make sure that the font number is a valid ROM FONT.