Frequently Asked Questions

Q. How can you configure USB to UART chip to allow this to work in a special baud rate?

FTDI provide both D2XX and VCP drivers in Windows OS. With the D2XX driver, the user is only required to fill in the baud rate in the second parameter when they call FT_SetBaudRate API. With the VCP driver however, the user will be required to modify the ftdiport.inf file for the special baud rate. Application Note 120 – Aliasing VCP Baud Rates describes how to calculate the divisor for a non-standard baud rate.

Q. When routing USB signals, what are the best practices for protection and PCB routing?

USB signals need to be as short as practical with matched length and routed as a 90-ohm differential pair between the USB connector and the FTDI chip. The USB interfaces on all of our FTDI products are rated up to 2KV range for ESD sensitivity. External ESD protection is recommended. Ensure that the ESD devices are specified for USB use. Some ESD devices have a high capacitance which will adversely affect the USB signal integrity.

Q. Is there an evaluation module available for the Power delivery Products?

FTDI is planning on releasing an evaluation module  (UMFT4233HPEV and UMFT233HPEV )in the near future to accompany its latest generation of USB Power Delivery ICs.


Q. What are the differences between the original FT232H and the FT232HP?

The FT232HP offers the same functionality as the FT232H. It can be used for UART, bit bang, I2C/SPI via MPSSE, etc. The FT232HP offers additional power delivery functionality. This allows for control of power direction which can be either supplied from the USB Host or the device. The same applies to all ‘HP’ variants. The original FT232H only had the ability to get power from the USB Host.

Q. Should I select the new Power Delivery version of the IC for my new project?

The PD versions of the FT232H/FT2232H/FT4232H offer all the same data features whilst having much more flexibility in the power supply. Therefore, if your device requires more than 5V at 500mA to be supplied over USB, or if your device currently has its own power supply of up to 20V at 3A which you want to eliminate, you could consider the PD version.


Q. Can I just load the D2XX drivers and run a D2XX application on a newly installed Linux system?

No, the VCP driver is likely enabled by default on most distributions.  Before running a Linux D2XX application, the VCP driver must be unloaded as follows:sudo rmmod ftdi_sio / sudo rmmod usbserial. Do not use the -f  (force remove) option.

Q. When using VDAP/V2DAP or VDPS/V2DPS, What is the correct format for the WRF arguments and following data?

It’s recommended to specify the data type prior to writing data to a file with WRF.  If ASCII (IPA) is selected, then each character is changed to its ASCII value and sent to the file – RED text is sent to the VNC1L or VNC2 monitor: IPA<CR>  D:\> OPW TEST.TXT<CR>  D:\>  WRF 4<CR> TESTD:\> CLF TEST.TXT<CR> D:\>. When HEX (IPH) input values are used, then hex values are sent, usually with the short command set (SCS).  Note that the number of bytes specified with WRF (0x08) is a double-word (4-bytes): IPH<CR> D:\> SCS<CR> D:\> 09 20 54 45 53 54 2E 54 53 53 0D     3E     08 20 00 00 00 04 0D      54 45 53 54 3E     0A 20 54 45 53 54 2E 54 53 53 0D     3E. When testing command sequences with a terminal program, select one that can send hex values directly, such as CoolTerm (

Q. Is there a recommended crystal to use with FT4222H?

The UMFT4222EV uses an X32F-G18QA-12.000 crystal.

This is a 12.000 MHz from CN-ELectronics  X32F series

With the parameters:

Package = 3.2 x 2.5
Frequency = 12.000000 MHz
Frequency Tolerance @ 25°C =   ±30 ppm
Frequency stability Tolerance over Operating Temperature Range = ±20 ppm
Operating Temperature Range  = -40°C to +85°C
Drive Level = 10µW to 100µW
Max Equivalent series Resistance (ESR)  < 80 Ohms
Max Shunt Capacitance (C0) < 7pF
Load Capacitance (CL) = 18pF

Q. How to detect when enumeration has completed via hardware?

Most FTDI devices use a PWREN# signal. It will be high (power = off) under the following conditions: -The device is in reset OR -The device is not yet configured by USB enumeration, or the USB enumeration sequence has failed OR -The host PC system is in the USB suspend state

Q. Does the FT260 provide a Virtual COM Port over HID class?

The FT260 does not present a Virtual Com Port on the host PC. The device is a HID class device rather than an FTDI Vendor Class device and therefore does not require the FTDI drivers to be loaded. The LibFT260 library provided by FTDI can be used by an application to control the UART, GPIO and I2C Master functions of the device. The FT260 can also be interfaced using HID requests directly from the application.

Q. With the latest drivers two sets are supplied for i386 and AMD64. For Win 64 and Intel processor should we be using the i386 drivers?

Drivers should be installed automatically (by Windows). If you choose to do this manually, if you specify the higher level folder and choose to search sub-directories it should be chosen automatically.

So you shouldn’t need to specify the exact driver files.

The architecture is named after AMD because AMD invented it, with the Athlon 64. Similarly, the 32-bit i386 architecture is named after Intel’s 386 processor, because it was the first of its kind, but i386 will also work on AMD processors.

Even if you have an intel CPU, AMD64 is what you’d use to install 64-bit on your computer (it uses the same instruction sets).

Q. What is the maximum SPI clock rate when using FT4222H?

The maximum SPI interface operating clock can be set up to 40MHz in master mode and 20MHz in slave mode. The SPI clock rate is subject to system clock and the SPI clock_div.

Q. How can I submit my driver for certification?

Microsoft® instituted a device driver certification process to ensure the drivers are functional with their products. Many FTDI customers are interested in changing the FTDI drivers to reflect their corporate identity. This can be done via editing FTDI’s INF files, however, once an INF file has been edited, its original digital signature is no longer valid and needs to be certified. Please see AN_101: Submitting Modified FTDI Drivers for Windows Hardware Certification for a guide on the certification. Please note that Microsoft may update their process and should be supported by Microsoft.

Q. What external EEPROM is recommended for use with the FTDI USB Hi-Speed ICs?

For the FT2232H and FT4232H, a 93C46, 93C56 or 93C66 is recommended. The FT232H requires the 93C56 or 93C66. All of these serial EEPROMs need to be specified or configured for 16-bit word and 3.3V I/O operation. There are many manufacturers of this type of device, and FTDI does not have a preference.