Dilshan R Jayakody’s Web Log

Logic analyzers are allowing us to monitor and /or diagnose a large number of digital signals simultaneously and these devices are essential when developing complex digital systems. In this project we design simple 8 channel USB logic analyzer with Windows version of driver software. Design of this logic analyzer is based around Future Technology Devices FT245 USB FIFO chip. With the given oscillator this system takes 14MSPS (Mega samples per second) and this system is design to work as (USB) self powered device (without any external power source). Driver part of this project is based on FTD2XX driver and GUI is developed using Delphi. Current version of driver software is design to work with Windows NT operating systems and it is highly recommended to use it with 1360 × 768 or with higher video resolutions (with aspect ratio of 16:9). This design also contains real-time logic level indicators to monitor "low frequency" signal levels and construction of that portion i...

Universal Serial Bus (USB) allows peripherals and computers to interconnect using standard protocol and provide plug and play feature to the devices. At the moment there are 2 specifications available for USB they are, USB 1.1 : In this specification data transfer rate is 12Mbps and 1.5Mbps. USB 2.0 : Support data transfer rate up to 480Mbps. Both these specifications support up to 127 devices and support for hot swapping (no need to power down to remove or connect the devices). In USB devices are categorized as a classes and each class represent the functionality that target device can provided to the host device. For example: AUDIO : Audio and related systems HID : Human Interface Devices. (E.g: Keyboard, Mouse, etc) POWER: Devices related with the power such as UPS systems. IrDA: Infrared devices. There are 4 types of transfers take place over USB, Control transfer : Used to configure the bus and devices on the bus. Bulk transfer : Move data asynchronously over USB. Isochron...

According to my experiences USB devices are bit complicated to design and writing software (drivers and support applications) for USB devices are time consuming and complex process. Most recommended (and easiest) method to design hardware interface for USB port is using Future Device Technologies FT245 or FT232 chips. At the moment both these chips support for USB 2.0 and have excellent set of APIs. To test the performance of this device I implement some experimental version of PC oscilloscope using FT245 USB Interface, AD7575 ADC, LF347 Op-amp, 4069 Hex Inverter and array of AM7205 FIFOs. Application program is design using Delphi 7 and it is totally based on FTDI Delphi APIs. This test system is worked perfectly in Windows XP and Windows 2003 systems during my test runs and produce excellent results. I choose FT245 for this design because it has 8 parallel input interfaces and this is perfectly matched with AD7575 ADC. (AD7575 also have 8 parallel outputs) I use 2705 FIFOs to captur...