This development board, based on the FTDI FT232H chipset, can be used to manage external digital devices,
such as sensors, LEDs, displays, buzzers. This card provides synchronous/asynchronous serial connections, in this page we will mainly use it to manage external digital devices via
I2C protocol and
SPI protocol using its USB interface.
Note that this card provides 16 GPIO-type digital inputs/outputs that will be used to manage simple external digital components, such as relays.
Unfortunately, this board does not support external analog devices, in order to solve this lack we will use, on another page, another development board suitable for this purpose.
Before managing this development board, we need to make sure that the Operating System recognizes it correctly. Below we will face the problems on installing USB drivers in the Microsoft Windows operating system and in a router, assuming that whoever has minimum manual skills in managing the Linux operating system may make this development board visible to the operating system itself.
As soon as we insert this development board into a USB socket on a computer with a Microsoft Windows operating system, the operating system will recognize it as a serial device, that is, as a COMx port. This could be useful for those who want to manage this development board as a simple USB-Serial adapter, but in this case we need the USB drivers to manage this device as a real external USB device. To do this, we need to perform the following steps:
To manage this board we need the Python language, so we need to install Python on computer by performing the following steps:
c:\Python37-32\Lib\site-packages\usb>python Python 3.7.1 (v3.7.1:260ec2c36a, Oct 20 2018, 14:05:16) [MSC v.1915 32 bit (Intel)] on win32 Type "help", "copyright", "credits" or "license" for more information. >>> import usb.core >>> usb.core.find() <DEVICE ID 0403:6014 on Bus 000 Address 001>If the "DEVICE ID" is not returned or if an error is returned, see the next paragraph dedicated to errors.
As soon as we plug this development board into a USB socket on a router with a Linux operating system, the operating system will recognize it as a USB device. We can open a Telnet or SSH terminal to connect to the router and type the command "dmesg", an example of the output of the above command is the following:
usb 3-1.3: new high-speed USB device number 7 using ehci-platform usbcore: registered new interface driver usbserial usbcore: registered new interface driver usbserial_generic usbserial: USB Serial support registered for generic usbcore: registered new interface driver option usbserial: USB Serial support registered for GSM modem (1-port)
Then we enter the command "lsusb", an example of the output of the above command is the following:
Bus 003 Device 007: ID 0403:6014
To manage this board we need the Python language, therefore we need to install Python in the router, by performing the following steps:
admin@RT-AC86U:/# python3 Python 3.7.4 (default, Oct 03 2019, 21:10:12) [GCC 7.4.0] on linux Type "help", "copyright", "credits" or "license" for more information. >>> import usb.core >>> usb.core.find() <DEVICE ID 0403:6014 on Bus 003 Address 007>If the "DEVICE ID" is not returned or if an error is returned, see the next paragraph dedicated to errors.
If the Python interpreter does not recognize the development board or if an error is returned, then we need to activate the DEBUG mode within the Python interpreter to understand what is the problem. Open the Python interpreter and execute the following four instructions "import os", "os.environ ['PYUSB_DEBUG'] = 'debug' ", "import usb.core", "usb.core.find()" - an example of output of the above four instructions is as follows:
admin@RT-AC86U:/# python3
Python 3.7.4 (default, Oct 03 2019, 21:10:12)
[GCC 7.4.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import os
>>> os.environ['PYUSB_DEBUG'] = 'debug'
>>> import usb.core
>>> usb.core.find()
2021-01-05 18:01:09,600 ERROR:usb.libloader:'Libusb 1' could not be found
2021-01-05 18:01:09,603 ERROR:usb.backend.libusb1:Error loading libusb 1.0 backend
2021-01-05 18:01:09,620 ERROR:usb.libloader:'OpenUSB library' could not be found
2021-01-05 18:01:09,621 ERROR:usb.backend.openusb:Error loading OpenUSB backend
2021-01-05 18:01:09,671 ERROR:usb.libloader:'Libusb 0' could not be found
2021-01-05 18:01:09,673 ERROR:usb.backend.libusb0:Error loading libusb 0.1 backend
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/opt/lib/python3.7/site-packages/usb/core.py", line 1297, in find
raise NoBackendError('No backend available')
usb.core.NoBackendError: No backend available
The above-mentioned error "No backend available" is mainly displayed on a router as the Python USB module cannot
find the system USB libraries that are required to manage the connected external USB devices - the Entware libraries are located in the "/opt/lib" folder
and not in the router's libraries folder (which is usually "/usr/lib").
In order to solve this problem:
admin@RT-AC86U:/# python3 Python 3.7.4 (default, Oct 03 2019, 21:10:12) [GCC 7.4.0] on linux Type "help", "copyright", "credits" or "license" for more information. >>> import os >>> os.environ['PYUSB_DEBUG'] = 'debug' >>> import usb.core >>> usb.core.find() 2021-01-12 20:11:21,259 DEBUG:usb.backend.libusb1:_LibUSB.__init__(<CDLL '/opt/lib/libusb-1.0.so.0', handle 9e22d0 at 0x9bd8c0>) 2021-01-12 20:11:21,260 INFO:usb.core:find(): using backend "usb.backend.libusb1" 2021-01-12 20:11:21,260 DEBUG:usb.backend.libusb1:_LibUSB.enumerate_devices() 2021-01-12 20:11:21,260 DEBUG:usb.backend.libusb1:_LibUSB.get_device_descriptor(<usb.backend.libusb1._Device object at 0x9cfe00>) <DEVICE ID 0403:6014 on Bus 003 Address 007>
To recognize the FTDI device, first of all we need to run the command "pip install pyftdi"
to install the dedicated Python module PyFTDI (for more information on this module, refer to
this Internet site).
Then open the Python interpreter and run the following two
instructions "from pyftdi.ftdi import Ftdi"
and "Ftdi.show_devices()" - an example of the output of the above two instructions is the following:
admin@RT-AC86U:/# python3 Python 3.7.4 (default, Oct 03 2019, 21:10:12) [GCC 7.4.0] on linux Type "help", "copyright", "credits" or "license" for more information. >>> from pyftdi.ftdi import Ftdi >>> Ftdi.show_devices() Available interfaces: ftdi://ftdi:232h:3:8/1 (Single RS232-HS)
In the above output, the line "ftdi://ftdi:232h:3:8/1" provides with the FTDI address of
the development board - this address will be used in Python scripts to manage devices connected to this development board.
If the "No backend available" error appears in the above output, then refer to the paragraph "Errors on recognition of the development board" on
this page to solve the above-mentioned error.
The I2C mode is the most important mode that we will consider since with this mode we will be able to manage many external devices by connecting them to this development board. The I2C mode, in this reference development board, is enabled by shorting the pins AD1 and AD2 (see image for more details). All I2C devices have at least 4 connectors, listed below:
| Image | Development Board | External Device |
|---|---|---|
|
AD0 | SCL |
| AD1 + AD2 | SDA | |
| +5V / +3.3V | VCC / V+ | |
| GND | GND |
Since I2C mode reserves AD0-AD2 pins, only the AD3-AD7 and AC0-AC9 pins are available as GPIO pins on this reference development board. These pins could be used by external devices to activate some options or modes, such as resetting the external device.
In I2C mode it is possible to manage the external device, connected to this development board, through a hexadecimal address, used by all Python scripts to manage external devices. To get the hexadecimal address of the external device, go to the PyFTDI website and download the following Python script. Once downloaded, run it via the Python interpreter. An example of the output of the above script is the following:
admin@RT-AC86U:/# python3 i2cscan.py 0 1 2 3 4 5 6 7 8 9 A B C D E F 0: . . . . . . . . . . . . . . . . 1: . . . . . . . . . . . . . . . . 2: . . . . . . . . . . . . . . . . 3: . . . . . . . . . . . . . . . . 4: . . . . . . . . . . . . . . . . 5: . . . . . . . . . . . . R . . . 6: . . . . . . . . . . . . . . . . 7: . . . . . . . . .
In the above example, the hexadecimal address of the device is "5D". Note the "R" indicating that the device is read-only (the example device is a temperature sensor). If a "W" appears in place of the "R", then we can write to the external device.
The SPI mode is the other most important mode that we will consider since, even with this mode, we will be able to manage external devices by connecting them to this development board. SPI devices all have at least 5 connectors, listed below (see image for more details):
| Image | Development Board | External Device |
|---|---|---|
|
AD0 | SCLK / SCK |
| AD1 | MOSI / SDO / DO | |
| AD2 | MISO / SDI / DI | |
| AD3 | CS / SS | |
| +5V / +3.3V | VCC / V+ | |
| GND | GND |
Since SPI mode reserves the AD0-AD3 pins, only the AD4-AD7 and AC0-AC9 pins are available as GPIO pins on this reference development board. These pins could be used by external devices to activate some options or modes, such as resetting the external device.
Since some Python scripts require the presence of the Adafruit CircuitPython library (a fork of the MicroPython library), instructions for its installation are provided below. To install this library, execute the command "pip install Adafruit-Blinka", also keep in mind the following installation guidelines as this library requires necessarily, to properly work with the FT232H development reference board, the presence of the environment variable "BLINKA_FT232H=1" (more information can be found on the Adafruit website):
Then open the Python interpreter and run the following two instructions "import board" and "dir(board)" - an example of the output of the above two instructions is the following:
admin@RT-AC86U:/# python3 Python 3.7.4 (default, Oct 03 2019, 21:10:12) [GCC 7.4.0] on linux Type "help", "copyright", "credits" or "license" for more information. >>> import board >>> dir(board) ['C0', 'C1', 'C2', 'C3', 'C4', 'C5', 'C6', 'C7', 'D4', 'D5', 'D6', 'D7', 'I2C', 'MISO', 'MOSI', 'SCK', 'SCL', 'SCLK', 'SDA', 'SPI', '__builtins__', '__cached__', '__doc__', '__file__', '__loader__', '__name__', '__package__', '__spec__', 'ap_board', 'board_id', 'detector', 'pin', 'sys']
The two instructions display the pins supported by the Adafruit CircuitPython library for the reference development board, pins from "C0" to "D7" are the GPIO pins, while pins from "I2C" to "SPI" are the pins reserved for I2C and SPI modes.
Since some Python scripts require the presence of the Pillow module (a fork of the Python Imaging Library), instructions for installing it are provided below.
