Lpc2000

Sutton Mehaffey wrote:

>Thanks Richard.
>
>I think I discovered 99% of the problem.  Apparently, I was shipped
>samples of the Serial RAM FM24C256 chip that were true 5V parts and I
>asked for 3.3V.  Makes it a little difficult to get the chip to work
>:)  But, I will also change my pullups when I get the correct chip in.
> They are too high.  
>
>I've been a software designer for many years and I am trying to learn
>more about the hardware side and do some of the design myself.  I
>found I don't learn how the hardware works as well if I have someone
>else do all the hardware design.  So, sometimes I miss some things in
>the datasheet that are very important (4.7K pullups instead of 10K). 
>It's fun to learn, though.
>
>  
>

That's how we all did it, you can learn all you want in schools, but 
until you get into the real world ...

I've learned a lot by looking at other's designs, heh, I do not "know it 
all" and it is is fun to learn new stuff!

Enjoy,

TomW

>Sutton
>
>
>
>--- In lpc2000@yahoogroups.com, "rtstofer" <rstofer@...> wrote:
>  
>
>>--- In lpc2000@yahoogroups.com, "Sutton Mehaffey" <sutton@> wrote:
>>    
>>
>>>Charles,
>>>
>>>Using 10K pullups.
>>>
>>>      
>>>
>>10k isn't a pull-up when applied to I2C.  The absolute maximum that
>>might work on a good day is about 4.7k and a more realistic value is
>>    
>>
>2.2k.
>  
>
>>You never provided a link to the RAM device (that I recall) but in
>>looking at the FM24CL64, they recommend a 1.1k pull-up.  The reason it
>>is so small is the lower VDD.  Normally, at 5V VDD the pull-up can go
>>as low as 2k, maybe 1.8k.  At 3.3V the resistor would be somewhat
>>    
>>
>smaller.
>  
>
>>But, again, I don't know which device you are using.
>>
>>Richard
>>
>>    
>>
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>Yahoo! Groups Links
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-- 
Tom Walsh - WN3L - Embedded Systems Consultant
http://openhardware.net, http://cyberiansoftware.com
"Windows? No thanks, I have work to do..."
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