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JamesW, kent, England Guest
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Serial RAM (5V ideally) |
Posted: Thu Jun 11, 2009 8:11 am |
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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
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treitmey
Joined: 23 Jan 2004 Posts: 1094 Location: Appleton,WI USA
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Posted: Thu Jun 11, 2009 8:24 am |
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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) |
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JamesW, kent, England Guest
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Posted: Thu Jun 11, 2009 8:34 am |
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It is rather cool!
Can you recommend any particular part number, FRAM seems to throw up hundreds of parts
Cheers
James |
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treitmey
Joined: 23 Jan 2004 Posts: 1094 Location: Appleton,WI USA
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JamesW, kent, England Guest
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Posted: Tue Jun 16, 2009 3:54 am |
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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 |
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JamesW, kent, England Guest
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Posted: Thu Jun 25, 2009 5:31 am |
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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 |
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treitmey
Joined: 23 Jan 2004 Posts: 1094 Location: Appleton,WI USA
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JamesW, kent, England Guest
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Posted: Thu Jun 25, 2009 10:10 am |
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I'll have a look at the I2c - currently using 3k3 pullups and hardware i2c.
I'll give high speed a try.
Cheers
James |
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