Serial RAM (5V ideally)

[JamesW, kent, England]

Hi folks,

I have an application that is using a digital still camera (ITM C-328 - v.good cheap serial camera worth a look) to take a picture and upload it to the internet.

The camera takes a jpg image (pre-compressed and ready to save) and you download it serially.

All working fine, but.......

I am currently saving the image (anything from 9Kb to 35kb depending on detail) to I2C eeprom.

This works great other than the 5ms per byte write time to the eeprom - which means for a 32k image it takes a very long time.

In my head I believe the solution is to use ram instead of rom, which will speed it up greatly.

However I cannot find a 5V I2C ram device anywhere!

Can anyone suggest such a device (I could live with spi if I had to, but all such devices I find don't work on 5V).

Or is there an easy method of interfacing a 5V pic with 3V memory?

Thanks

James

Current s

[treitmey]

That app is SCREAMING try FRAM
Should be a drop in replacement for something like a 24LC256.
Its a little more $$, but it has 0 wait writes and reads.

note:0 wait, means 0 wait in terms of I2C.
(Its faster then the I2C bus)

[JamesW, kent, England]

It is rather cool!

Can you recommend any particular part number, FRAM seems to throw up hundreds of parts

Cheers

James

[treitmey]

I use the Ramtron FM24C256-G that uses the same 'wide' 'SO8W footprint of a 24FC256-I/SM
http://www.mouser.com/Search/Refine.aspx?Keyword=24FC256-I%2fSM
http://www.mouser.com/Search/Refine.aspx?Keyword=FM24C256-G

[JamesW, kent, England]

Excellent - thanks for the help (sorry for the delay in replying, been at the Le Mans 24H race all weekend)

I will get some on order and try it.

I'll let you know how much it improves the speed.

Cheers

James

[JamesW, kent, England]

Awesome RAMS - thanks for the advice.

(note to anyone else - they are wider fooprint than the standard eeprom - for once in my life a [spam] up on the board worked in my favour, as I'd used the wider footprint by mistake and had to stretch the eeproms).

With the camera staring at a fixed image....


Using eeproms to save the image (640 x 480 full colour jpeg)
(Time to take photo and save to memory 138 seconds.)

Using the FRAMS 6 seconds!!!!!

Shame the application is limited by the speed of a GPRS connection. I am buying in some modem samples with EDGE tecnhology built in

If anyone wants a look at a couple of images taken

www.embeddeddesigns.demon.co.uk/pix


Cheers again

James

[treitmey]

Nice pictures.
Have you ramped up the I2C speed?

[JamesW, kent, England]

I'll have a look at the I2c - currently using 3k3 pullups and hardware i2c.

I'll give high speed a try.

Cheers

James