The Analog Devices EVAL_AD7746EB is a low cost evaluation board for the AD7746 capacitance to digital converter. This board uses a Cypress FX2 as a USB-I2C bridge. The kit ships with a Windows GUI that provides basic control of the device. The GUI is written in LabView and Analog has provided this code as a demo. They do not provide support for communicating with this board using other means.
This code provides a simple example of how to communicate with the board using fxload and libusb in C under Linux, using the Analog-provided FX2 firmware.
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Install prerequisites:
sudo apt-get install libusb-dev sudo apt-get install fxload -
Optional: You can skip this step and just use the firmware file in this repo. Download and install the Analog Devices EVAL-AD7746 software for Windows. Grab this firmware file and copy it to ./firmware/Icv_usb.hex:
C:\Program Files (x86)\Analog Devices\AD7745-46EB\data\Icv_usb.hex -
Build and install.
make sudo make install
Plug the board into USB and run the example program:
$ ./eval_ad7746eb
time: 1593624499.785889 capacitance_raw: 80f720 capacitance_pF: 0.061781 temp_raw: 8434629 temp_C: 22.471
time: 1593624499.956193 capacitance_raw: 80f697 capacitance_pF: 0.061647 temp_raw: 8434684 temp_C: 22.498
time: 1593624500.181381 capacitance_raw: 80f6b2 capacitance_pF: 0.061674 temp_raw: 8434666 temp_C: 22.489
time: 1593624500.417508 capacitance_raw: 80f6f0 capacitance_pF: 0.061734 temp_raw: 8434689 temp_C: 22.500
time: 1593624500.643616 capacitance_raw: 80f693 capacitance_pF: 0.061644 temp_raw: 8434671 temp_C: 22.492
or log data to a file:
./eval_ad7746eb > data.log 2>/dev/null
You can modify the config_ad7746() and config_board() functions as needed for your application.
When the eval board is plugged in, the udev rule will invoke fxload to load the firmware. You can check that the device was detected:
$ lsusb -d 0456:b481
Bus 001 Device 003: ID 0456:b481 Analog Devices, Inc.
You should see something like this in syslog indicating firmware was loaded:
$ tail /var/log/syslog
Jul 1 16:19:59 hostname kernel: [74691.005245] usb 1-1: new high-speed USB device number 16 using musb-hdrc
Jul 1 16:19:59 hostname kernel: [74691.153842] usb 1-1: New USB device found, idVendor=0456, idProduct=b481, bcdDevice= 0.00
Jul 1 16:19:59 hostname kernel: [74691.153890] usb 1-1: New USB device strings: Mfr=0, Product=0, SerialNumber=0
Jul 1 16:20:00 hostname root: AD7746EB firmware loaded.
There was a note in the Analog docs that the USB microcontroller would lock up if the I2C communication fails. I did not see any failures, but beware.
If the device is unplugged or a communication failure occurs the program will exit.
The settings in config_ad7746() are specific to my application. You will need to change them for your hardware.