USB interface

What kind of RAM?

(E.g., static RAM is certainly much easier than DRAM...)

Cypress semiconductor CY7C1069DV33 static ram. I want to Write to it from an heart rate transmitter, an accelerometer used as a pedometer and a few pushbutton switches. I want to sample at 1 khz or 100 hz.. Then I want to load the data into the computer for sports fitness analysis. I guess I could also write GPS data to one of the bits.

Bob

The data comes from heart beats and steps and switches. 4 mega bytes is the desired size. I have a tentative device selected. From the PC the unit should look like a usb drive with one 4 mega byte file on it and require no drivers other than what is in windows. I is to be a sports data logger.

Bob

rt.

how

You understand this is in TSOP or BGA, right? Are you building the board, or somebody else will? You will need a uC to read/write the RAM anyway. So, just use the same uC to talk to the PC. You need an USB uC. But I would suggest serial RAM instead of this static RAM.

uld

You understand this is in TSOP or BGA, right? Are you building the board, or somebody else will? You will need a uC to read/write the RAM anyway. So, just use the same uC to talk to the PC. You need an USB uC. But I would suggest serial RAM instead of this static RAM.

The memory write does not require an UC. No data analysis is done in the device. I would like to avoid an UC for the read. The write will be controlled by a 1khz clock and a 22 bit counter. the interface will be some signal conditioning of commercially available devices. and some data synchronizers. The signal conditioning will depend on the input device. Physical size is not an issue.

Bob

to

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me

If you don't want uC, then you need FPGA with USB IP core. It is very difficult to build USB stack/mass storage device with discrete logics.

If you don't want uC, then you need FPGA with USB IP core. It is very difficult to build USB stack/mass storage device with discrete logics.

Would you suggest any particular devices for the usb side, 3 volt.

How did the data get into the RAM in the first place, what ever size it is ?

There must be some sort of logic involved, or are you looking for a 4Mb device ??

don

Best answer yet.

now

re

quoted text -

Atmel's At90usb82 (8K flash) can do minimum usb mass storage. At90usb162 (16K) would be plenty of code space. There are lots of other chips as well.

Atmel's At90usb82 (8K flash) can do minimum usb mass storage. At90usb162 (16K) would be plenty of code space. There are lots of other chips as well.

TUSB3210?

Bob

And quite costly from an engineering perspective, let alone PCB real estate.

USB does not operate at 3 Volts.

Which company has cheap MB size serial RAM? The only one I know of is the nice ferroelectric nonvolatile RAM from Ramtron:

But is is expensive, e.g. 2MBit for $24.13 at Mouser, compared to about $5 for the same size for standard SRAM.

Should have said serial memory rather than this parallel memory.

Yes, if the OP needs the speed, true serial RAM would be expensive. But for 1KHz sample rate, serial Flash is more than enough to meet his need.

The device that connects to the usb does.

Bob

You *could* use a USB-to-RS232 chip, except ...

You need a microcontroller (or an FPGA, but a uC is a lot cheaper).

There's no practical way to build a USB drive with a RAM chip and discrete logic. The least impractical way to do it with discrete logic would be to build a microcontroller out of said discrete logic.

Which can be written to sans µP?

You can use a nice cheap serial flash to store the data (32 MBit parts are avaialble). Use an FTDI chip or module to do the USB interface. You might be able to get the FTDI part to talk directly to the serial flash but as others have suggested the only rational way to this project is to use a small micro to glue the flash, data source and USB interface together. You can do it with an FPGA but it's more work and more cost for parts. You'll need a lot more than a counter to control the memory device - RAM is simpler to control but harder to interface with USB. I have just done a similar job with a 2M byte 10nS RAM, FPGA and FTDI high speed USB module but eventually I need > 12Mbytes/second transfer rate - there is no way I would have used the FPGA for 1k bytes/s.

Michael Kellett