Using bus B pins

[melvyn2]

I'm looking to use this library with the Tigard, which uses both buses of the FT2232H. Specifically, AD0-6 are used for the UART and logic analyzer breakout, while BD0-6 are used for SWD/JTAG/I2C/SPI breakouts and more. However, this library seems to only provide access to pins ad0-7, which means that, for example, I would have to use the UART breakout for SPI and would not be able to use the other bus simultaneously. Is support for the B bus planned?

[geomatsi]

IIRC (e.g. see FTDI AN184) FT2232H ~ FT232H + FT232H. In fact, if you plug FT2232H board into your Linux machine, you will get two ttyUSB serial ports unless you disable ftdi_sio driver.

So you should be able to use this crate for both channels of FT2232. For channel A see ws2812 example. Channel B can be accessed along the same lines.

For example, create device for Channel A:

        if #[cfg(feature = "ftdi")] {
            let device_a = ftdi::find_by_vid_pid(0x0403, 0x6010)
                .interface(ftdi::Interface::A)
                .open()
                .unwrap();
        } else if #[cfg(feature = "libftd2xx")] {
            let device_a = libftd2xx::Ft2232h::with_description("Dual RS232-HS A").unwrap();
        } else {
            compile_error!("one of features 'ftdi' and 'libftd2xx' shall be enabled");
        }

And now device for Channel B:

        if #[cfg(feature = "ftdi")] {
            let device_b = ftdi::find_by_vid_pid(0x0403, 0x6010)
                .interface(ftdi::Interface::B)
                .open()
                .unwrap();
        } else if #[cfg(feature = "libftd2xx")] {
            let device_b = libftd2xx::Ft2232h::with_description("Dual RS232-HS B").unwrap();
        } else {
            compile_error!("one of features 'ftdi' and 'libftd2xx' shall be enabled");
        }

After that you should be able to use device_a and device_b independently, accessing D0..D7 lines (ADBUSx on Channel A and BDBUSx on Channel B) as ad0..ad7 on each channel and using them for gpio/i2c/spi.

What you can not do with this crate at the moment is to access higher GPIOH0..GPIOH7 lines which are ACBUSx on Channel A and BCBUSx on Channel B. It should be fairly straightforward to add support for them, e.g. see similar archived project ftdi-embedded-hal-archive. Though note that those lines can only be used as GPIO.

Regards, Sergey

[melvyn2]

Thank you - I was using libftd2xx which didn't have the interface select option. Looking again, ftdi-rs using the open-source libftdi1 seems like a better choice anyways.

[newAM]

Yeah, in my experience if you're on Linux then the open source driver is better. The only advantage of libftd2xx is the ease of driver installation on Windows.

[geomatsi]

Thank you - I was using libftd2xx which didn't have the interface select option. Looking again, ftdi-rs using the open-source libftdi1 seems like a better choice anyways.

I would suggest to check my example above for the channel B:

        if #[cfg(feature = "ftdi")] {
            let device_b = ftdi::find_by_vid_pid(0x0403, 0x6010)
                .interface(ftdi::Interface::B)
                .open()
                .unwrap();
        } else if #[cfg(feature = "libftd2xx")] {
            let device_b = libftd2xx::Ft2232h::with_description("Dual RS232-HS B").unwrap();
        } else {
            compile_error!("one of features 'ftdi' and 'libftd2xx' shall be enabled");
        }

Probably "Dual RS232-HS B" will do the trick.

As for the choice between libftd2xx and libftdi, I would suggest to try both and make your choice for your hardware. In some cases libftd2xx behavior looks more predictable, e.g. see additional flushes.

Regards, Sergey

[melvyn2]

Yes, I understand how to select bus with libftd2xx as well now - I simply meant to explain why I hadn't seen how to do so from the examples. I understand each driver/library has its advantages, but considering that I am developing on linux as well as usability features as shown, I will likely stick to libftdi for now. Thank you for the clarification.