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CBUS bit bang mode of FT232R

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Full Member level 2
Oct 18, 2008
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Hi friends! Anybody who succeed to make FT232RL work in CBUS bit bang mode?

datasheet of FT232 said:
The CBUS pins can also be individually configured as GPIO pins, similar to asynchronous bit bang mode.
It is possible to use this mode while the UART interface is being used, thus providing up to 4 general
purpose I/O pins which are available during normal operation. An application note, AN232R-01, available
from FTDI website (FTDI Chip Home Page) describes this feature
I want to use 4 CBUS pins as GPIO pins while I m using the UART function. According to datasheet, it must be possible but how? I emailed to support@ftdi 2 days ago, they have not reply yet. Here is my email:

I have prototyped FT232RL bus powered configuration and installed combined model driver, I can switch between VCP and D2XX driver by using FT_PROG eeprom programmer. In VCP mode uart functions perfectly but I have problems about how to activate CBUS bit bang mode. CBUS bit bang mode requires D2XX commands. Do I need to switch to D2XX driver? If so, will the uart function continue to work or is there a way to use CBUS pins as GPIO while the device is still in VCP mode?

There is a visual C++ example for CBUS bit bang mode in your website. I have set CBUS pins as IO pins. Then, I have swithced to D2XX by using FT_PROG (comport is disappeared from device manager list and I checked the device in Usbview utility so that I make sure that the device is still recognized by the computer) I have downloaded example c++ program mentioned above. I double clicked exe output in release folder of the project, a form is appeared, there is a combobox in the form to list available FT devices, when I click it an error window appears: No FT232R or FT245R devices found. Any idea will be welcome.

Abovementioned application note does not give detailed information about CBUS bit bang mode.
Thank you for your reading this long post, any comment will be wellcome.

I've used FTDI chips in many of my projects, but I never actually used that particular feature.

However, I have been collecting reference material and projects implementing that feature:

Introduction to FTDI bitbang mode

On ATMega328 Bootloading With FTDI Bitbang Method

libFTDI - FTDI USB driver with bitbang mode

FT232: FTDI's Bit Bang using Python

I assume you have already downloaded and read FTDI's appnotes concerning the subject, so I'm not going to bother posting those links.

I hope this info helps you in your endeavor, keep me posted on your progress, this feature has always interested me.

Hi! Thanks for the answer bigdogguru. CBUS bit bang mode is different than sync/async bit bang mode. CBUS bit bang mode can be used along with UART interface. My primary interface is UART and it works well. I try to make use of additional 4 bit parallel interface. There are some people using sync/async bit bang mode of the device but I have not seen one using cbus bit bang mode yet.
They replied my email after I sent a reminding email. I write last advancement not to leave off my topic although I have not resolved the problem.
They ask me to recompile the project(source file is available)! I do not have visual C++ compiler, I have downloaded Visual C++ Express ed. from microsoft's website and tried to compile. It gave an error pertaining to absence of MFC library. Because I did not want to dive into microsoft's library I gave it up for now. By the way, I dont know wheter MFC is free or not. Thanks.

Did you mean, that FT232R isn't recognized if D2XX + CBUS BitBang is configured in the EEPROM? So if you set standard D2XX mode, it shows up in the example application?

You said, you didn't have standard Visual C++. What's your intended method to operate the FT232R in D2XX mode? You don't necessarily need Visual C++, but any tool, that can cooperate with FTD2XX.dll. You can perform the enumeration of available FTDI devices in your own application as well.

Thanks for the answer FvM. Yes, I set D2XX mode and configured cbus pins as IO in the eeprom but example program can not list the device in the listbox. I m sure that device is recognized by the computer(usbview utility checks) but not by the example application.
I thought I can use these 4 IO pins via provided example. I did not intend to write my own program. I looked for a simple way, I hoped that example .exe works but it did not. I may retry in the future. If I succeed to work it in a way, I will post it.

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