Lpc2000

Currently I have an LPC2129 and am trying to use the P0.2/SCL and 
P0.3/SDA/Eint1 pins for GPIO.

Running the software under simulation in KEIL shows the micro correctly 
changing the states of these pins however once applied to the physical 
chip on a board we've designed in house there's no signal - basically  
ground with a little noise. I've been over the schematics (as I didnt 
design this board) and there appears to be nothing obviously wrong. 
However given both of these pins are potentially used for I2C I was 
wondering if they additionally need pull-ups but I can't see anything 
anywhere in the errata etc to explicitly say they do...

Anyone had a similar problem with these particular pins? (I'm using 
P0.4, P0.5 etc for the same form of output to drive relays and they're 
all working fine).

Do you have a pull up on P0.2 as it is open drain for I2C compliance??


Michael J. Frazier
Software Engineer
Governors America Corp.
+1.413.786.5600 (Voice)
+1.413.789.7736 (Fax)

[Non-text portions of this message have been removed]

Currently there are no pull ups on either P0.2 or P0.3... we're not using
I2C but I'm guessing they're still required even for GPIO use.

-----Original Message-----
From: lpc2000@yahoogroups.com [mailto:lpc2000@yahoogroups.com]On Behalf
Of mfrazier@...
Sent: 03 March 2006 14:41
To: lpc2000@yahoogroups.com
Subject: Re: [lpc2000] LPC2129 GPIO issues with P0.2 and P0.4


Do you have a pull up on P0.2 as it is open drain for I2C compliance??


Michael J. Frazier
Software Engineer
Governors America Corp.
+1.413.786.5600 (Voice)
+1.413.789.7736 (Fax)

[Non-text portions of this message have been removed]




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--- In lpc2000@yahoogroups.com, "Andrew Berney" <amb@...> wrote:
>
> Currently there are no pull ups on either P0.2 or P0.3... we're not
using
> I2C but I'm guessing they're still required even for GPIO use.
> 

You have to put pullups on each pin that can be used with I2C since
these pins are open collector.
I found a similar problem using LPC2138 (it has 2 I2C units so there
are 4 open collector pins).
Effectively this is written in VERY small character in the pin
configuration section of user manual.
Regarding other pins you have to pull them (to gnd or vcc) if they are
programmed as inputs, to avoid a floating voltage.

Carlo Barbaro

Aye having just applied a couple of 2k2 resistors to pull the signals up on
the board they both work fine. All the inputs are pulled low atm.
Now I simply have to slap our resident hardware engineer for not putting the
input of our front panel switch on an IRQ line.

Cheers for the quick reply.

Andy

-----Original Message-----
From: lpc2000@yahoogroups.com [mailto:lpc2000@yahoogroups.com]On Behalf
Of c.barbaro
Sent: 03 March 2006 15:39
To: lpc2000@yahoogroups.com
Subject: [lpc2000] Re: LPC2129 GPIO issues with P0.2 and P0.4


--- In lpc2000@yahoogroups.com, "Andrew Berney" <amb@...> wrote:
>
> Currently there are no pull ups on either P0.2 or P0.3... we're not
using
> I2C but I'm guessing they're still required even for GPIO use.
>

You have to put pullups on each pin that can be used with I2C since
these pins are open collector.
I found a similar problem using LPC2138 (it has 2 I2C units so there
are 4 open collector pins).
Effectively this is written in VERY small character in the pin
configuration section of user manual.
Regarding other pins you have to pull them (to gnd or vcc) if they are
programmed as inputs, to avoid a floating voltage.

Carlo Barbaro







Yahoo! Groups Links

Andrew,
    2k pull ups are a bit low...you should use a 10k to start with to be 
safe.

Mike

[Non-text portions of this message have been removed]

Aye agreed, however I didnt have any surface mount ones to hand at the time
and simply wanted to check a practical application of the theory on our dev
board here. 2k2's worked well enough to prove it and the final drawings will
have this modified with the correct parts (most likely 10K pull ups I
imagine - not looked at whats ideally requried) to correct it
pre-fabrication.

Cheers though :)

Andy

-----Original Message-----
From: lpc2000@yahoogroups.com [mailto:lpc2000@yahoogroups.com]On Behalf
Of mfrazier@...
Sent: 03 March 2006 16:10
To: lpc2000@yahoogroups.com
Subject: RE: [lpc2000] Re: LPC2129 GPIO issues with P0.2 and P0.4


Andrew,
    2k pull ups are a bit low...you should use a 10k to start with to be
safe.

Mike

[Non-text portions of this message have been removed]




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