Interfacing to a Cypress EZ-USB CY7C68013A FX2LP

[granta1969]

Hello. I've been intersted in the various development programs that you can create for the Cypress EZ-USB FX2LP device. Mostly 8 channel logic anaylizers and oscilloscopes.

If you don't know what a Cypress EZ-USB FX2LP is, then you're in for a treat. It's an amazingly dynamic and diverse chip that generally comes on a very small development board with a single high/full speed usb 2 interface and it has 24 digital pins that have a maximum bandwidth of 24mhz each. It has a built in enhanced 8051 microprocessor and it gets it's pid/vid from an external eeprom chip which is read when the device is first powered on. if no external eeprom is present it reads it's pid/vid from hard coded internal memory and the device will default as a ez-usb device.

Two companies currently use it for 24mhz logic analyzers, Saleae and EZUsb. Unfortunately, they have been subject to many cheap clones flooding the markplace which has cut into their profits. Thats one drawback to the device. It's not easy to protect it against counterfeiting because the way these devices work is that you can either store your program on the external eeprom (kinda limited to the eeprom size) or else it gets loaded (instantly) from the software on your pc.

The great thing about this device is that you can find ultra cheap ez-usb deveopment boards on e-bay from China for as little as £5 or $7 (usa). I own a few of these. I have an original Saleae Logic device, 2 ez-usb development boards from China, a Saleae clone (from china) that only cost £6.50 shipped (it comes in a little case with some logic cables and a good usb cable with a filter - i was impressed) and an original Saleae Logic device ($150).

They all work exactly the same and give really great results for just about any kind of logic analysis. The Saleae Logic software is really great! I've been using mine to read I2S audio streams from a Silicon Labs CP2114 development board. All the devices can read the I2S Clock, Frame and Data lines perfectly. I've been really impressed with it and it's been a lot of fun.

Having said all that, I have to say that the Cypress development software is not the most enjoyable cup of tea I've ever drank. It comes with a free version of Keil development tools found in their development kit which does allow up to 4k of program data to be compiled. That could be enough for most. You can also download an evaluation version direclty from keil.com however the free one they offer is limited to 2k of data.

I've been interested in Flowstone for a good long while now and every time I go to use my Logic Analyzer I can't help but think of all the intersting things that could be accomplished with Floswtone. Some of the more advanced versions of the Saleae Logic come with an onboard ADC so it also works as an Oscilloscope. However the chip they have selected is limited to 20mhz but not bad for most DIY home users.

I've made all sorts of hardware mods for my own boards including designing a shield that lets you switch between two EEprom and has buffer input using a CD4050BPW Hex Non-Inverting Buffer which lets you input digital signals that run as high as 18volts. Currently all boards run at 3.3 volts with what they describe as 5 volt tolerant. But I prefer not to input anything over 3.3 volts into the pins. As you probably know any cd4050 will limit/buffer the digital output to whatever you power the chip with (i.e., 3.3v in this case). Logic and EZ-USB both use a terrible method of dealing with higher voltages and that is by using a diode network or diode array chip which is basically a "clamp" which protects the pins from both static and high voltage by sending the diodes directly to the 3.3 volts. Anything greater than 3.3 volts gets eaten up by the Vss of the driving current of the chip which means the whole chips will have it's voltage raised (briefly), but you certainly couldn't apply 12volts to this kind of input for any length of time or else you'd destroy the chip.

So I've allready improved the design and I'm surprised no one else has bothered to do this before. Overall I find it an amazing little device with huge amounts of potential to do all kinds of things. The logic analyzers mentioned are only using 8 of the 24 pins that are available. I've been intersted in adding in a Analog Devices AD9288BSTZ-100 ADC chip. It's a cheap (under £6), easy to come by ADC chip that you find in many hand held 50mhz oscilloscopes.

I'm curious if anyone would be intersting in such a project. There is allready an open source Anaylizer dedicated to this board but it's development is moving at a snails pace. Not a lot activity going on with it. I think Flowstones graphic interface will lend to some excitement. Perhaps DSPRobotics would even consider adding in an EZ-USB interface into their product?

take it easy,

Grant