Future Technology Devices International Ltd. Application Note AN_131 FT2232D/H Fast Opto-Isolated Serial Interface Mode Document Reference No.: FT_000187 Version 1.0 Issue Date: 2009-10-21 This application note describes how to use the FTDI FT2232D and FT2232H devices in Fast Opto-Isolated Serial Interface mode Future Technology Devices International Limited (FTDI) Unit 1,2 Seaward Place, Glasgow G41 1HH, United Kingdom Tel.: +44 (0) 141 429 2777 Fax: + 44 (0) 141 429 2758 E-Mail (Support): [email protected] Web: http://www.ftdichip.com Copyright © 2009 Future Technology Devices International Limited Document Reference No.: FT_000187 FT2232D/H Fast Opto-Isolated Serial Interface Mode Application Note AN_131 Version 1.0 Clearance No.: FTDI# 116 Table of Contents 1 Introduction .................................................................... 2 2 Hardware Configuration .................................................. 3 3 2.1 Pin Assignment Of Fast Opto-Isolated Serial Interface ............. 4 2.2 IO Timing .................................................................................. 5 Software Configuration ................................................... 6 3.1 4 5 EEPROM Setting ........................................................................ 6 Application Development ................................................ 8 4.1 Code example ........................................................................... 9 4.2 Write Data Mode ..................................................................... 10 4.3 Read Data Mode ...................................................................... 11 Contact Information ...................................................... 13 Appendix A - Revision History ............................................ 15 Copyright © 2009 Future Technology Devices International Limited 1 Document Reference No.: FT_000187 FT2232D/H Fast Opto-Isolated Serial Interface Mode Application Note AN_131 Version 1.0 Clearance No.: FTDI# 116 1 Introduction This application note illustrates how to use the FTDI FT2232D or FT2232H in a Fast Opto-Isolated Serial Interface mode. This mode provides a method of communicating with an external device over USB using 4 wires that can have opto-isolators in their path, thus providing galvanic isolation between systems. Copyright © 2009 Future Technology Devices International Limited 2 Document Reference No.: FT_000187 FT2232D/H Fast Opto-Isolated Serial Interface Mode Application Note AN_131 Version 1.0 Clearance No.: FTDI# 116 2 Hardware Configuration EEPROM Configuration: Both of FT2232D and FT2232H device require an external 93C46 EEPROM organized in 16-bit words. They also support the 93C56 and 93C66 EEPROMs organized in 16-bit words. Opto-Isolation Device connection setting: Use a USB cable to connect an FT2232D or FT2232H device to a PC - the pin assignment in given in Table 2-1 which gives details of the required connection between the external system and FT2232D or FT2232H device. Figure 2-1 is an example opto-isolated circuit; it shows two Agilent HCPL-2430 (see the semiconductor section at www.agilent.com) high speed opto-couplers used to optically isolate an external device which interfaces to USB using the FT2232D. In this example VCC5V is the USB VBUS supply and VCCE is the power supply to the external device. Care must be taken with the voltage used to power the photo-LEDs. This must be the same voltage as the FT2232D I/Os are driving to, or the LEDs may be permanently on. Limiting resistors should be fitted in the lines that drive the diodes. The outputs of the opto-couplers are open-collector and require a pullup resistor. Figure 2-1 Fast Opto-Isolated Serial Interface Example Copyright © 2009 Future Technology Devices International Limited 3 Document Reference No.: FT_000187 FT2232D/H Fast Opto-Isolated Serial Interface Mode Application Note AN_131 Version 1.0 Clearance No.: FTDI# 116 2.1 Pin Assignment Of Fast Opto-Isolated Serial Interface If either channel A or channel B of the FT2232D/H is enabled in Fast Opto-Isolated Serial mode then the pins on channel B are switched to the fast serial interface configuration. The I/O interface for fast serial mode is always on channel B, even if both channels are being used in this mode. An address bit is used to determine the source or destination channel of the data. It therefore makes sense to always use at least channel B or both for fast serial mode, but not A own its own. Table 2-1 is the pin assignment of channel B when it is in Fast Opto-Isolated Serial Mode. Pin# Pin# Pin Pin Name (FT2232D) (FT2232H) Definitions 40 38 BDBUS0 FSDI Type Description INPUT Fast serial data input 39 39 BDBUS1 FSCLK INPUT Clock input to FT2232D or FT2232H chip to clock data in or out. The external device has to provide a clock signal or nothing will change on the interface pins. This gives the external device full control over the interface. It is designed to be half duplex so that data is only transferred in one direction at a time. 38 40 BDBUS2 FSDO OUTPUT Fast serial data output. 37 41 BDBUS3 FSCTS OUTPUT Clear To Send control signal output. Driven low to indicate that the chip is ready to send data Table 2-1 Channel B Fast Serial Interface Configured Pin Descriptions Note: FSDI & FSCLK are Pulled up to VCCIO via internal 200K resistors. These pins can be programmed to gently pull low during USB suspend (PWREN# = “1”) by setting this option in the EEPROM. Copyright © 2009 Future Technology Devices International Limited 4 Document Reference No.: FT_000187 FT2232D/H Fast Opto-Isolated Serial Interface Mode Application Note AN_131 Version 1.0 Clearance No.: FTDI# 116 2.2 IO Timing When either Channel B or both Channel A and B are configured in Fast Opto-Isolated Serial Interface mode, it’s necessary to follow the IO timing as shown in Figure 2-1 to access the data. Table 2-2 shows the detail information for the timing. Figure 2-1 Fast Opto-Isolated Serial Interface Signal Waveforms Time Description Min Max Unit t1 FSDO / FSCTS hold time 5 - ns t2 FSDO / FSCTS setup time 5 - ns t3 FSDI hold time 5 - ns t4 FSDI setup time 10 - ns t5 FSCLK low 10 - ns t6 FSCLK high 10 - ns t7 FSCLK Period 20 - ns Table 2-2 Fast Opto-Isolated Serial Interface Signal Timings Copyright © 2009 Future Technology Devices International Limited 5 Document Reference No.: FT_000187 FT2232D/H Fast Opto-Isolated Serial Interface Mode Application Note AN_131 Version 1.0 Clearance No.: FTDI# 116 3 Software Configuration With FTDI devices, it is necessary to install the FTDI D2XX driver on the PC to which they are connected. Please visit http://www.ftdichip.com/Drivers/D2XX.htm and download and install the necessary driver which matches the PC. The table below is taken from the FT2232H datasheet. It indicates that it is necessary to set the Fast Opto-Isolated Serial Interface mode by configuring the EEPROM to Fast Serial Interface mode before developing a software application to access data under Fast Opto-Isolated Serial Interface mode. Configuring the EEPROM is illustrated in chapter3.1. Developing software application is illustrated in chapter4 ASYNC ASYNC SYNC ASYNC SYNC Fast Serial Serial MPSSE 245 FIFO 245 FIFO Bit-bang Bit-bang Interface UART EEPROM configured Application Software configured YES YES YES YES YES YES YES CPUStyle FIFO Host Bus Emulation YES YES YES Table 3-1 Configuration Using EEPROM And Application Software 3.1 EEPROM Setting Connect the FT2232D or FT2232H to a PC via USB cable, if the driver is installed already, the EEPROM settings can be programmed using either FTDIs MPROG or FT_PROG utilities (downloadable from FTDI website. Any one of these utilities can be used to set port A and port B to “OPTO Isolate” mode in EEPROM. Figure 3-1 illustrates using MPROG for an example of FT2232D setting. It is possible to configure channel B or both channel B and A to fast Opto-Isolated Serial interface mode by clicking the right side ‘OPTO Isolate’ item (please check the red square). Copyright © 2009 Future Technology Devices International Limited 6 Document Reference No.: FT_000187 FT2232D/H Fast Opto-Isolated Serial Interface Mode Application Note AN_131 Version 1.0 Clearance No.: FTDI# 116 Figure 3-1 EEPROM setting by MProg tool Note. When channel B is not in Fast Opto-Isolated Serial Mode, it is not possible to configure channel A as Fast Opto-Isolated Serial Mode. If only one Fast Opto-Isolated Serial port is needed, then use channel B. Channel A can be configured in another IO mode if channel B is in Fast Opto-Isolated Serial Mode. If both Channel A and Channel B are in Fast Opto-Isolated Serial Mode all of the IO will be on Channel B. Copyright © 2009 Future Technology Devices International Limited 7 Document Reference No.: FT_000187 FT2232D/H Fast Opto-Isolated Serial Interface Mode Application Note AN_131 Version 1.0 Clearance No.: FTDI# 116 4 Application Development It is necessary to develop an application to access data under Fast Opto-Isolated Serial Interface mode. The following section describes how this can be achieved. The code examples are for illustration only and are not supported by FTDI. Before developing the application, check Table 4-1 to determine which value is “Mode” is assigned to for Fast Opto-Isolated Serial Interface mode. When Fast Opto-Isolated Serial Interface mode is selected, set mode=0x10 will hold the device mode in reset and set mode=0x0 will release device from reset. This is different from other modes. So When an application is developed , it is recommended to call FT_SetBitMode(0x10) will hold the system in freeze then call FT_SetBitMode(0x0) to free it. Table 4-1 Mode Value With FT_SetBitMode Command To use the software commands, it is necessary to download the ftd2xx.dll, ftd2xx.lib, ftd2xx.h from the FTDI CDM driver. Details are available in the following programmers guide on how to use the software commands D2XX_Programmer's_Guide(FT_000071).pdf. In the example application code, it is firstly necessary to open the Fast Opto-Isolated Serial Port of the FT2232D or FT2232H. Copyright © 2009 Future Technology Devices International Limited 8 Document Reference No.: FT_000187 FT2232D/H Fast Opto-Isolated Serial Interface Mode Application Note AN_131 Version 1.0 Clearance No.: FTDI# 116 4.1 Code example The following section gives an application example. This code is not guaranteed and is provided for illustration only. It is not supported by FTDI. Example code FT_HANDLE ftHandle; FT_STATUS ftStatus; UCHAR Mask = 0x00; UCHAR Mode; ftStatus = FT_Open(1, &ftHandle); //open port B if(ftStatus != FT_OK) { // FT_Open failed return; } Mode = 0x00; //reset mode ftStatus = FT_SetBitMode(ftHandle, Mask, Mode); if (ftStatus == FT_OK) { //access data from here } else { // FT_SetBitMode FAILED! } FT_Close(ftHandle); Copyright © 2009 Future Technology Devices International Limited 9 Document Reference No.: FT_000187 FT2232D/H Fast Opto-Isolated Serial Interface Mode Application Note AN_131 Version 1.0 Clearance No.: FTDI# 116 4.2 Write Data Mode When a PC sends data to an external system via FT2232D or FT2232H device, it is referred to as write data mode. To send fast serial data out of the FT2232D or FT2232H, the external device must drive the FSCLK clock. If the FT2232D or FT2232H has data ready to send, it will drive FSDO output low to indicate the start bit. It will not do this if it is currently receiving data from the external device. This is illustrated in Figure 4-1. Figure 4-1 Fast Opto-Isolated Serial Interface Output Data Format Notes : 1. The first bit output (Start bit) is always 0. 2. FSDO is always sent LSB first. 3. The last serial bit output is the source bit (SRCE). It indicates which channel the data has come from. A ‘0’ means that it has come from Channel A, a ‘1’ means that it has come from Channel B. 4. if the target device is unable to accept the data when it detects the START bit, it should stop the FSCLK until it can accept the data. Copyright © 2009 Future Technology Devices International Limited 10 Document Reference No.: FT_000187 FT2232D/H Fast Opto-Isolated Serial Interface Mode Application Note AN_131 Version 1.0 Clearance No.: FTDI# 116 4.3 Read Data Mode When a PC reads data from an external system via FT2232D or FT2232H device, it is referred to as read data mode. An external device is allowed to send data into the FT2232D or FT2232H if FSCTS is high. On receipt of a zero START bit on FSDI, the FT2232D or FT2232H will drop FSCTS on the next positive clock edge. The data from bits 0 to 7 are then clocked in (LSB first). The last bit (DEST) determines where the data will be written to. The data can be sent to either channel A or channel B. If DEST= ‘0’, the data is sent to channel A, (assuming channel A is enabled for fast serial mode, otherwise the data is sent to channel B). If DEST= ‘1’ the data is sent to channel B, (assuming channel B is enabled for fast serial mode, otherwise the data will go to channel A. (Either channel A, channel B or both channels must be enabled as fast serial mode or the function is disabled). This is illustrated in Figure 4-2. Figure 4-2 Fast Opto-Isolated Serial Interface Input Data Foramt Notes : 1. The first bit input (Start bit) is always 0. 2. FSDI is always received LSB first. 3. The last received serial bit is the destination bit (DEST).It indicates which channel the data should go to. A ‘0’ means that it should go to channel A, a ‘1’ means that it should go to channel B. 4. The target device should ensure that FSCTS is high before it sends data. FSCTS goes low after data bit 0(D0) and stays low until the chip can accept more data. Copyright © 2009 Future Technology Devices International Limited 11 Document Reference No.: FT_000187 FT2232D/H Fast Opto-Isolated Serial Interface Mode Application Note AN_131 Version 1.0 Clearance No.: FTDI# 116 Contention There is a possibility that contention may occur, where the interface goes from being completely idle to both sending and receiving at the same clock instance. In this case the FT2232D/H will back off, and allows the data from the external device to be received. Data Format The data format for either direction is :1) Zero Start Bit 2) Data bit 0 3) Data bit 1 4) Data bit 2 5) Data bit 3 6) Data bit 4 7) Data bit 5 8) Data bit 6 9) Data bit 7 10) Source/Destination (‘0’ indicates channel A; ‘1’ indicates channel B) Copyright © 2009 Future Technology Devices International Limited 12 Document Reference No.: FT_000187 FT2232D/H Fast Opto-Isolated Serial Interface Mode Application Note AN_131 Version 1.0 Clearance No.: FTDI# 116 5 Contact Information Head Office – Glasgow, UK Future Technology Devices International Limited Unit 1,2 Seaward Place, Centurion Business Park Glasgow G41 1HH United Kingdom Tel: +44 (0) 141 429 2777 Fax: +44 (0) 141 429 2758 E-mail (Sales) [email protected] E-mail (Support) [email protected] E-mail (General Enquiries) [email protected] Web Site URL http://www.ftdichip.com Web Shop URL http://www.ftdichip.com Branch Office – Taipei, Taiwan Future Technology Devices International Limited (Taiwan) 2F, No. 516, Sec. 1, NeiHu Road Taipei 114 Taiwan , R.O.C. Tel: +886 (0) 2 8791 3570 Fax: +886 (0) 2 8791 3576 E-mail (Sales) [email protected] [email protected] E-mail (Support) E-mail (General Enquiries) [email protected] Web Site URL http://www.ftdichip.com Branch Office – Hillsboro, Oregon, USA Future Technology Devices International Limited (USA) 7235 NW Evergreen Parkway, Suite 600 Hillsboro, OR 97123-5803 USA Tel: +1 (503) 547 0988 Fax: +1 (503) 547 0987 E-Mail (Sales) [email protected] E-Mail (Support) [email protected] Web Site URL http://www.ftdichip.com Branch Office – Shanghai, China Future Technology Devices International Limited (China) Room 408, 317 Xianxia Road, Shanghai, 200051 China Tel: +86 21 62351596 Fax: +86 21 62351595 E-mail (Sales) [email protected] E-mail (Support) [email protected] E-mail (General Enquiries) [email protected] Web Site URL http://www.ftdichip.com Copyright © 2009 Future Technology Devices International Limited 13 Document Reference No.: FT_000187 FT2232D/H Fast Opto-Isolated Serial Interface Mode Application Note AN_131 Version 1.0 Clearance No.: FTDI# 116 Distributor and Sales Representatives Please visit the Sales Network page of the FTDI Web site for the contact details of our distributor(s) and sales representative(s) in your country. Vinculum is part of Future Technology Devices International Ltd. Neither the whole nor any part of the information contained in, or the product described in this manual, may be adapted or reproduced in any material or electronic form without the prior written consent of the copyright holder. This product and its documentation are supplied on an as-is basis and no warranty as to their suitability for any particular purpose is either made or implied. Future Technology Devices International Ltd will not accept any claim for damages howsoever arising as a result of use or failure of this product. Your statutory rights are not affected. This product or any variant of it is not intended for use in any medical appliance, device or system in which the failure of the product might reasonably be expected to result in personal injury. This document provides preliminary information that may be subject to change without notice. No freedom to use patents or other intellectual property rights is implied by the publication of this document. Future Technology Devices International Ltd, Unit 1, 2 Seaward Place, Centurion Business Park, Glasgow G41 1HH United Kingdom. Scotland Registered Number: SC136640 Copyright © 2009 Future Technology Devices International Limited 14 Document Reference No.: FT_000187 FT2232D/H Fast Opto-Isolated Serial Interface Mode Application Note AN_131 Version 1.0 Clearance No.: FTDI# 116 Appendix A - Revision History Revision History Version 1.0 Initial Release 21/10/2009 Copyright © 2009 Future Technology Devices International Limited 15